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Peer Reviewed
Aircraft Wings and Morphing–Evolution of the Concepts
This is a peer-reviewed entry published in Encyclopedia Journal, full entry can be found at 10.3390/encyclopedia5030101

This encyclopedia entry provides an updated appreciation of the evolution of morphing aircraft wings, organized as follows: first, lift concepts are briefly examined; second, patents related to lift enhancement are discussed, showcasing existing technology and its evolution; finally, several technologies for morphing wings and the role of UAVs as testbeds for many innovative concepts are highlighted. The background of morphing wings is presented through a recap of lift concepts and the presentation of representative patents that describe the evolution of leading-edge and trailing-edge devices, such as flaps, slats, spoilers, and control surfaces. Although these topics are not usually detailed in reviews of morphing wings, they are deemed relevant for this encyclopedia entry.

morphing airfoil aircraft wing leading edge trailing edge
Morphing, or the ability to change shape, aims to enhance or introduce new vehicle system performance characteristics suited to varying conditions. It generally targets two objectives: maximizing efficiency at all flight stages and facilitating different missions requiring distinct aircraft [1]. Morphing is recognized as one of twenty-five new technologies and operational improvements relevant to “green aviation” [2]. Morphing aircraft can adapt to multi-objective mission profiles, allowing them to operate more efficiently; but the adoption of morphing solutions requires attention to weight and life cycle costs, further to safety.
As with many engineering disciplines, aircraft design involves compromises among various flight condition requirements. For example, Sadraey [3] lists eighteen design constraints and requirements relevant to aircraft design, including aircraft types, maneuverability, pilot control, weight, and takeoff run, each further divided into several sub-items. A design cannot be optimized for all possible flight situations.
Wing design frequently addresses different requirements, such as takeoff and cruise phases, by incorporating movable components. Traditional solutions involving mechanisms to move parts separate from the wing’s main body, such as leading-edge slats and trailing-edge flaps, have been used for a long time. These components create a variable airfoil geometry to meet different flight needs, such as achieving higher lift or lower drag [4]. Conventional hinged control surfaces and high-lift devices that entail discrete geometry changes are often not regarded as morphing. In that sense, morphing refers to structures that undergo continuous geometric changes as a whole.
Morphing involves changes to the airframe configuration aimed at enhancing vehicle performance. There are various types and intensities of morphing. After observing the wing-sweep capability in flight—such as in the Grumman F-14 and the General Dynamics F-111—Abate and Shyy note “However, nearly all aircraft exhibit more subtle forms of morphing, such as flap deployment and retractable landing gear” [5]. In these scenarios, morphing is categorized as “active” to distinguish it from “passive” morphing, which occurs when changes in vehicle configuration do not depend on the pilot or control system, as seen in wing bending during parking or flight.
Morphing focuses on geometrical changes that optimize the fulfillment of mission profiles. While there is no universally accepted definition of morphing, discussions sometimes include conventional slats and flaps—a point that remains contentious, as many researchers argue that traditional control surfaces and high-lift devices do not belong in this category; in a stricter sense, morphing encompasses actuators, mechanisms and structures, flexible skins, and control, which may not always be integrated simultaneously [6][7]. A NATO Research and Technology Organization (RTO) publication defines morphing as a “real-time adaptation to enable multi-point optimized performance,” shifting the definition from the mechanics of morphing to the enhanced capabilities offered by a morphing vehicle (McGowan et al. [8]).
Since conventional control surfaces provide essential context for the subject, this encyclopedia entry includes them as a reference, even though they are frequently omitted from morphing discussions.
The industry’s adoption of advanced morphing technologies necessitates evidence of safety levels comparable to those of conventional control surface systems, along with aerodynamic performance and enhancements in weight and installation impact [9]. Due to the smaller scale of many unmanned aerial vehicles (UAVs) and the less stringent certification and safety constraints compared to other aviation sectors, UAVs serve as ideal platforms for innovative concepts and testing new structural solutions [10].
The growing interest in morphing aircraft is driven by the variety of new materials, including composites, rubbers, shape memory alloys (SMAs) and shape memory polymers (SMPs) in addition to traditional aeronautical materials such as aluminum alloys. Many of these materials demonstrate properties that are tailored throughout their volume, as observed in functionally graded materials (FGMs).
The design of morphing wings encompasses various scientific and engineering disciplines and innovative attitudes. Morphing can involve adjustments to the airfoil cross-section and/or wing extension (span and chord) and necessitates proper kinematics, actuation, and fulfillment of power requirements. Numerous approaches exist, each varying in complexity and ambition. Morphing studies examine cross-section design—whether constant (rectangular planform) or varying from the fuselage to the wingtip- and utilize 2D or 3D modeling techniques, comparing leading-edge (LE) and/or trailing-edge (TE) morphing with changes implemented through control surfaces like slats, flaps, and Krueger flaps. Aerodynamic pressure analysis over the wing can be simulated using Computational Fluid Dynamics (CFD) software, such as XFOIL, and interactions with wing torsion and bending are modeled comprehensively to account for aerodynamic loading, skin, reinforcement structures, and mechanisms. The optimization of morphed skin geometry, including local variations in skin thickness and adjustments in local radii, involves stress analyses in complex geometries and varying skin thickness, considering the materials used, which sometimes include less common options such as shape memory alloys or auxetic materials.
Wing morphing can be classified into three different forms of geometry alteration: (i) planform (span, chord, and sweep), (ii) out-of-plane (twist, dihedral/gull, and spanwise bending), and (iii) airfoil and profile transformations [7][11].
Vasista et al. published a critical review that compiled functional data related to various morphing-wing projects [12]. Especially noteworthy books include Smart, Intelligent Aircraft Structures (SARISTU) [13] edited by Wölcken and Papadopoulos and focused on a single EU research and development project, and Morphing Wing Technologies: Large Commercial Aircraft and Civil Helicopters [14] edited by Concilio et al., which remains one of the most thorough publications in this field. Adaptronics—Smart Structures and Materials by Sinapius [15], although not focused solely on wings, presents a comprehensive treatment of morphing.
Recent reviews of morphing wings include Li et al. [16], Ameduri and Concilio [17], Zhu et al. [18], Dong and Arief [19], and, focusing on developments in Japan, Tsushima and Tamayama [20]. These reviews are quite comprehensive; other reviews concentrate on specific aspects. For example, Mowla et al. [21] examine the use of artificial intelligence, Ahmad et al. [22] focus on polymer-based skins for morphing wing applications, and Ajaj et al. [23] investigate the aeroelasticity of morphing wings. This encyclopedia entry is not a substitute for those reviews. However, it addresses the background of the subject—the evolution of high-lift surfaces, such as flaps, slats, and Krueger flaps—which is typically not covered in the mentioned reviews but is relevant for an encyclopedia entry.
Emphasis will be placed on the morphing of wing cross-sections (airfoils). The following section outlines basic terminology and concepts related to this topic.

References

  1. Falcão, L.; Gomes, A.A.; Suleman, A. Aero-structural design optimization of a morphing wingtip. J. Intell. Mater. Syst. Struct. 2011, 22, 1113–1124.
  2. Agarwal, R.K. Review of technologies to achieve sustainable (green) aviation. In Recent Advances in Aircraft Technology; Agarwal, R.K., Ed.; InTech: London, UK, 2012; Chapter 19; pp. 424–464.
  3. Sadraey, M.H. Aircraft Design: A Systems Engineering Approach; Aerospace Series; Wiley: Chichester, West Sussex, UK, 2012.
  4. van Tooren, M.; Rao, A.G.; Obert, E.; van Buijtenen, J. Applied aerodynamics and propulsion foundations: Fixed wing vehicles. In Encyclopedia of Aerospace Engineering; Blockley, R., Shyy, W., Eds.; John Wiley & Sons: Hoboken, NJ, USA, 2010.
  5. Abate, G.; Shyy, W. Bio-inspiration of morphing for micro air vehicles. In Morphing Aerospace Vehicles and Structures; Valasek, J., Ed.; John Wiley & Sons: Chichester, West Sussex, UK, 2012; pp. 41–53.
  6. Reich, G.; Sanders, B. Introduction to morphing aircraft research. J. Aircr. 2007, 44, 1059.
  7. Sofla, A.Y.N.; Meguid, S.A.; Tan, K.T.; Yeo, W.K. Shape morphing of aircraft wing: Status and challenges. Mater. Des. 2010, 31, 1284–1292.
  8. McGowan, A.-M.R.; Vicroy, D.D.; Busan, R.C.; Hahn, A.S. Perspectives on highly adaptive or morphing aircraft. In Proceedings of the Morphing Vehicles Symposium RTO-MP-AVT-168, Évora, Portugal, 20–24 April 2009; Available online: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090017845.pdf (accessed on 1 April 2025).
  9. Apuleo, G. Aircraft morphing—An industry vision. In Morphing Wing Technologies: Large Commercial Aircraft and Civil Helicopters; Concilio, A., Dimino, I., Lecce, L., Pecora, R., Eds.; Butterworth-Heinemann: Oxford, UK, 2018; pp. 85–101.
  10. Gomez, J.C.; Garcia, E. Morphing unmanned aerial vehicles. Smart Mater. Struct. 2011, 20, 103001.
  11. Barbarino, S.; Bilgen, O.; Ajaj, R.M.; Friswell, M.I.; Inman, D.J. A review of morphing aircraft. J. Intell. Mater. Syst. Struct. 2011, 22, 823–877.
  12. Vasista, S.; Tong, L.; Wong, K.C. Realization of morphing wings: A multidisciplinary challenge. J. Aircr. 2012, 49, 11–28.
  13. Wölcken, P.C.; Papadopoulos, M. (Eds.) Smart Intelligent Aircraft Structures (SARISTU)—Proceedings of the Final Project Conference; Springer: Cham, Switzerland, 2016.
  14. Concilio, A.; Dimino, I.; Lecce, L.; Pecora, R. (Eds.) Morphing Wing Technologies: Large Commercial Aircraft and Civil Helicopters; Butterworth-Heinemann: Oxford, UK, 2018.
  15. Sinapius, J.M. Adaptronics—Smart Structures and Materials; Springer: Berlin/Heidelberg, Germany, 2021.
  16. Li, D.; Zhao, S.; Da-Ronch, A.; Xiang, J.; Drofelnik, J.; Li, Y.; Zhang, L.; Wu, Y.; Kintscher, M.; Monner, H.P.; et al. A review of modelling and analysis of morphing wings. Prog. Aerosp. Sci. 2018, 100, 46–62.
  17. Ameduri, S.; Concilio, A. Morphing wings review: Aims, challenges, and current open issues of a technology. Proc. Inst. Mech. Eng. Part C J Mech. Eng. Sci. 2020, 237, 4112–4130.
  18. Zhu, J.; Yang, J.; Zhang, W.; Gu, X.; Zhou, H. Design and applications of morphing aircraft and their structures. Front. Mech. Eng. 2023, 18, 34.
  19. Dong, C.; Arief, M.M. Morphing wing designs in commercial aviation. arXiv 2025, arXiv:2502.07182.
  20. Tsushima, N.; Tamayama, M. Recent researches on morphing aircraft technologies in Japan and other countries. Bull. JSME. Mech. Eng. Rev. 2019, 6, 19-00197.
  21. Mowla, M.N.; Asadi, D.; Durhasan, T.; Jafari, J.R.; Amoozgar, M. Recent advancements in morphing applications: Architecture, artificial intelligence integration, challenges, and future trends—A comprehensive survey. Aerosp. Sci. Technol. 2025, 161, 110102.
  22. Ahmad, D.; Parancheerivilakkathil, M.S.; Kumar, A.; Goswami, M.; Ajaj, R.M.; Patra, K.; Jawaid, M.; Volokh, K.; Zweiri, Y. Recent developments of polymer-based skins for morphing wing applications. Polym. Test. 2024, 135, 108463.
  23. Ajaj, R.M.; Parancheerivilakkathil, M.S.; Amoozgar, M.; Friswell, M.I.; Cantwell, W.J. Recent developments in the aeroelasticity of morphing aircraft. Prog. Aerosp. Sci. 2021, 120, 100682.
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Subjects: Engineering, Aerospace
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Sérgio M. O. Tavares
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Pedro V. Gamboa
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Paulo M. S. T. de Castro
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Online Date: 15 Jul 2025
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