Augmented Aircraft Performance with the Use of Morphing Technology for a Turboprop Regional Aircraft Wing.

biomimetics Article Augmented Aircraft Performance with the Use of Morphing Technology for a Turboprop Regional Aircraft Wing Frédéric Moens ONERA, The French Aerospace Lab, Aerodynamics Aeroelsaticity and Acoustics Department, 92190 Meudon, France; ; Tel.: +33-1-4673-4211 Received: 28 June 2019; Accepted: 5 September 2019; Published: 12 September 2019



 Abstract: This article presents some application of the morphing technology for aerodynamic performance improvement of turboprop regional aircraft. It summarizes the results obtained in the framework of the Clean Sky 2 AIRGREEN2 program for the development and application of dedicated morphing devices for take-off and landing, and their uses in off design conditions. The wing of the reference aircraft configuration considers Natural Laminar Flow (NLF) characteristics. A deformable leading edge morphing device (“droop nose”) and a multi-functional segmented flap system have been considered. For the droop nose, the use of the deformable compliant structure was considered, as it allows a “clean” leading edge when not used, which is mandatory to keep natural laminar flow (NLF) properties at cruise. The use of a segmented flap makes it possible to avoid external flap track fairings, which will lead to performance improvement at cruise. An integrated tracking mechanism is used to set the flap at its take-off optimum setting, and, then, morphing is applied in order to obtain a high-performance level for landing. Lastly, some performance improvements can be obtained in climb conditions by using the last segment of the flap system to modify the load distribution on the wing in order to recover some extended laminar flow on the wing upper surface. Keywords: morphing; droop nose; trailing-edge flap; Natural Laminar Flow wing 1. Introduction: The Different Uses of Morphing Technology for Aerodynamic Performance Enhancement 1.1. Use of Morphing Technology for Flight Control Since the beginning of aviation history, the use of deformable surfaces for controlling flight has been present. The most famous example is the Ader’s Eole airplane in which the design was inspired by an analogy of bat or bird wings (or Leonardo da Vinci drawings) (Figure 1). Surface shape modification by the use of flexible structures was used for flight control for most of the airplanes at this period (Figure 2). However, due to the increase of flight speed, and, consequently, of the dynamic pressure in flight conditions, these structures appear to be fragile and need to be reinforced, which leads to a dramatic increase of the weight of the deformation system. The use of rigid structures in combination with surface control elements became the standard. Note that, strictly speaking, the use of an aileron for flight control or the deployment of flaps or slats at take-off or landing phases can be considered as “morphing,” which means that the shape of the wing is modified in order to improve its performance for a flight “off design” condition. Currently, a shape is considered morphed if it includes deformation of the initial surface by the use of flexible materials or mechanical systems. Biomimetics 2019, 4, 64; doi:10.3390/biomimetics4030064 www.mdpi.com/journal/biomimetics Biomimetics 2019, 4, 64 Biomimetics 2019, 4, 64 2 of 20 2 of 21 (a) (b) Figure 1. How to fly? First ideas. (a) Leonardo da Vinci drawings [1]; (b) Clément Ader’s Avion III [2]. Surface shape modification by the use of flexible structures was used for flight control for most of the airplanes at this period (Figure 2). However, due to the increase of flight speed, and, consequently, of the dynamic pressure in flight conditions, these structures appear to be fragile and need to be reinforced, which leads to a dramatic increase of the weight of the deformation system. The use of rigid structures in combination with surface control elements became the standard. Note that, strictly speaking, the use of an aileron for flight control or the deployment of flaps or slats at take-off or landing phases can be considered as “morphing,” which means that the shape of the wing is modified in order to improve its performance for a flight “off design” condition. Currently, a shape (a) deformation of the initial(b) is considered morphed if it includes surface by the use of flexible materials or Figure mechanical systems. Figure How fly?First Firstideas. ideas.(a) (a)Leonardo LeonardodadaVinci Vinci drawings [1]; Clément Ader’s Avion [2]. 1. 1. How toto fly? drawings [1]; (b)(b) Clément Ader’s Avion IIIIII [2]. Surface shape modification by the use of flexible structures was used for flight control for most of the airplanes at this period (Figure 2). However, due to the increase of flight speed, and, consequently, of the dynamic pressure in flight conditions, these structures appear to be fragile and need to be reinforced, which leads to a dramatic increase of the weight of the deformation system. The use of rigid structures in combination with surface control elements became the standard. Note that, strictly speaking, the use of an aileron for flight control or the deployment of flaps or slats at take-off or landing phases can be considered as “morphing,” which means that the shape of the wing is modified in order to improve its performance for a flight “off design” condition. Currently, a shape is considered morphed if it includes deformation of the initial surface by the(b) use of flexible materials (a) or mechanical systems. Figure 2. Pioneer ages—Use morphing flight control surface. Wright brothers’ Flyer Figure 2. Pioneer ages—Use of of morphing forfor thethe flight control surface. (a)(a) Wright brothers’ Flyer [3],[3], Santos-Dumont’s Demoiselle (b)(b) Santos-Dumont’s Demoiselle [4].[4]. 1.2.1.2. Use of of Morphing Technology forfor Adaptation to Flight Conditions Use Morphing Technology Adaptation to Flight Conditions Later, introduction of of morphing technology onon military aircrafts hashas shown significant aircraft Later, introduction morphing technology military aircrafts shown significant aircraft performance improvements on a large spectrum of flight conditions. For instance, the use of a variable performance improvements on a large spectrum of flight conditions. For instance, the use of a swept wingswept in supersonic to improve performance transonic or low speed conditions is a variable wing inaircrafts supersonic aircrafts to improveatperformance at transonic or low speed good example (Figure 3). Biomimetics 2019,is 4, a 64good example (Figure 3). 3 of 21 conditions (a) (b) Figure 2. Pioneer ages—Use of morphing for the flight control surface. (a) Wright brothers’ Flyer [3], (b) Santos-Dumont’s Demoiselle [4]. 1.2. Use of Morphing Technology for Adaptation to Flight Conditions Later, introduction of morphing technology on military aircrafts has shown significant aircraft performance improvements on a large spectrum of flight conditions. For instance, the us (...truncated)