Wing-winglet assembly with uninterrupted flap system

Abstract

Sailplane having a wing and a wing-tip device provided at an outermost end of a lifting section of the wing, the wing-tip device comprising: a root having a root airfoil matching a wing airfoil of the outermost end of the lifting section of the wing; 5 a winglet portion extending upwardly relative to the lifting section of the wing at a cant angle; a curved transition section rigidly connecting the root and the winglet portion; and a wing-tip device trailing edge flap comprising one or more flap segments; wherein the wing-tip device trailing edge flap extends in a spanwise direction from the root, 10 throughout the curved transition section and at least partially into the winglet portion.

Description

[0001] Eisenfuhr Speiser

[0002] Munich, 20 February 2026

[0003] Our Ref.: AM 5754-02WO MEB / MEB

[0004] Applicant: Achleitner Aerospace GmbH

[0005] serial Number: PCT Application with priority A 60031 / 2025

[0006] Achleitner Aerospace GmbH

[0007] Linzer StraBe 413, 4070 EFERDING

[0008] AUSTRIA

[0009] Wing-winglet assembly with uninterrupted flap system

[0010] FIELD

[0011] The application relates to wing-tip devices in particular for sailplanes, wings for sailplanes having such wing-tip devices, and sailplanes having such wings or wing-tip devices.

[0012] BACKGROUND

[0013] 5 Sailplanes (also referred to as gliders) typically operate by gaining altitude in atmospheric updrafts, such as thermal updrafts, and then use the gained altitude to glide a certain distance, such as a distance to another updraft, where the altitude expended for the glide can be regained. The altitude that can be gained is limited, by physical constraints such as atmospheric conditions and human performance at altitude, as well as legal constraints for 0 example in the form of restricted air spaces at high altitudes. To convert the limited altitude into a maximum gliding distance, and therefore be competitive, sailplanes strive for an exceptionally high lift-to-drag ratio.

[0014] Moreover, atmospheric updrafts are typically small scale phenomena. In orderto effectively use such atmospheric updrafts, i.e. maximize the altitude gained from the updraft, the time 5 spent in the area of the updraft is to be maximized. This can for example be achieved by flying substantially straight and slow or by circling in the area of the updraft. While circling may extend the time spent in the area of the updraft at the pilot’s will, it is desired to minimize the circling radius and thereby make use of even the smallest scale updrafts. Thus, even when circling in an updraft, a low speed is desired during such flight phases.

[0015] Conversely, in order to maximize overall cross country flight distance, a high speed is desired when gliding between updrafts.

[0016] Winglets are a specific type of wing-tip device, which add aerodynamic surfaces to the tips of aircraft wings to improve performance by reducing induced drag caused by wingtip vortices. However, they do so at the cost of an increase in parasitic drag, and to some extent also interference drag. In orderto achieve a net drag benefit, it is therefore necessary to tailor winglets fora certain airspeed. For passenger aircraft, such as airline jets, winglets are optimized for cruise speed, because that is where these aircraft operate a majority of the time, and therefore the highest fuel savings can be achieved. Existing sailplane winglets on the other hand are typically optimized for a speed close to or at best glide speed. However, during cross country flying, sailplanes operate a significant amount of time at air speeds higher than the best glide speed, necessitated by the desire for maximizing the total distance flown. At higher air speeds, existing winglets optimized for best glide speed can become a net producer of drag when the increase in parasitic drag outweighs the reduction in induced (and interference) drag. Using the most recent sophisticated CFD techniques, it is currently believed that modern winglet designs can largely eliminate this penalty, so that innovation in sailplane winglet design has stalled in recent years.

[0017] Fig. 1 shows an exemplary prior art outboard wing section or wing-tip device 100 comprising a winglet. The configuration shown in Fig. 1 is in principle representative for many existing aircraft designs, including sailplanes. Wing section 100 comprises a root 110 at which the wing extends substantially in a spanwise direction SW. Root 110 can be part of or connect to a lifting section of the wing (not depicted). The lifting section of the wing is section of the wing that is configured to produce a majority of the wing’s lift, as is commonly known in the art for aircraft wings. In Fig. 1 , the lifting section of the wing is the omitted portion of the wing which continues from root 110 along spanwise direction SW inboard towards the fuselage (also not depicted). Root 110 has a root airfoil 112 matching a wing airfoil of the outermost end of the lifting section of the wing (not shown). When attached to the wing, root airfoil 112 marks the boundary between outboard wing section 100 and the main lifting section of the wing.

[0018] At an outboard end of outboard wing section 100, a winglet portion 120 is provided extending upwardly relative to the lifting section of the wing at a cant angle p, which can be measured relative to spanwise direction SW. The term “upward” is defined with respect to the orientation of the wing during normal flight. Therefore, the “upward” side of the wing is a side in the direction of which the wing is configured to produce lift. Winglet portion 120and root 110 are connected by a curved transition section 130. Transition section 130 provides a smooth or kink-free transition between root 110 which extends substantially in spanwise direction SW, and winglet portion 120 that extends substantially out of plane of root 110 at cant angle p. Fig. 1 also shows a trailing edge flap 140 that extends in spanwise direction SW over a portion of root 110. Trailing edge flap 140 is typically an actively controlled control surface, such as an aileron or flaperon.

[0019] Preferably, the term “inboard” generally denotes a relative position along spanwise direction SW closer to where the wing meets the aircraft’s fuselage. Conversely, the term “outboard” generally denotes a relative position along spanwise direction SW further away from where the wing meets the aircraft’s fuselage. Where portions of the wing or wing-tip device extend at a noticeable angle or curvature relative to spanwise direction SW in a plane perpendicular to the direction of flight DOF, such as in transition section 130 or winglet portion 120, “inboard” and “outboard” relate to a direction that follows this angle or curvature. For the purposes of this description, the term “direction of flight DOF” is used synonymously with a longitudinal axis of the aircraft.

[0020] Fig. 2 shows a further exemplary prior art outboard wing section or wing-tip device 100 comprising a winglet, which differs from that shown in Fig. 1 that a second trailing edge flap 150 is provided that extends over a portion of winglet portion 120. No trailing edge flap is present in curved transition section 130. That is, curved transition section 130 continuously extends between leading edge 132 and trailing edge 134 with an airfoil or series of airfoils of fixed geometry. In other words, the camber of the airfoil(s) in transition section 130 cannot be changed.

[0021] Preferably, the term “leading edge” refers to the forward-most edge of a wing or wing-tip device, wherein the “forward” direction is defined in the direction of flight or DOF (cf. Fig. 3). At the leading edge, at least when the DOF coincides with the direction of relative wind (i.e. at 0° angle of attack), the airflow is separated into an upper airflow portion flowing over an upper surface of the airfoil, and a lower airflow portion flowing over a lower surface of the airfoil. Preferably, the term “trailing edge” refers to the most rearward edge of a wing or wing-tip device at which, under ideal conditions, the airflow can last make contact with the airfoil. If the airfoil is free of gaps connecting the upper and lower surfaces, the trailing edge is the edge at which the upper and lower airflow portions separated by the leading edge meet again. The “rearward” direction is defined opposite to the direction of flight or DOF (cf. Fig. 3). Preferably, a “trailing edge flap” is a rearward portion of the airfoil that comprisesthe trailing edge, and which, during flight, be deflected relative to a forward portion of the airfoil.

[0022] Preferably, the “curved transition section” relates to a portion of a wing-tip device connecting root and winglet portion, in which - when viewed in a plane perpendicular to direction of flight DOF - the leading edge is curved relative to spanwise direction SW.

[0023] Designs similar to that shown in Fig. 2 are described for example in US 2011 / 0186689 A1 (US’889). In the designs known from US’889, the second trailing edge flap is an actively controlled control surface, with an actuator enclosed within the upper and lower aerodynamic surfaces of the winglet (cf. e.g. Fig. 3 of US’889). US’889 describes the winglet as an aftermarket modification. In US’889, the second trailing edge flap is employed to keep spanwise section loads at or below originally designed values for an existing wing without a winglet, to allow modifying the existing wing with an aftermarket winglet without the need for extensive structural wing modifications. In US’889, any gain in aerodynamic efficiency is attributed to the addition of a winglet as such.

[0024] In other prior art designs having a second trailing edge flap 150 similar to that shown in Fig. 2, this additional control surface is provided to effect yaw of the aircraft. To this end, means for actively changing the angle of flap 150 are provided, which are directly or indirectly operated by the pilot using the flight controls. In conventional sailplane design, such additional control surfaces that extend over a portion of winglet portion 120 are thought to have no benefits that would outweigh the effort of providing active control means in the narrow design space provided by the winglet. Their use is thus limited to tailless sailplanes, such as the Akaflieg Karlsruhe AK-X, where they are the only option for providing a rudder-like control surface for yaw authority.

[0025] Fig. 3 provides a three-view sketch of the AK-X configuration. To achieve its intended effect of providing yaw stability, winglet section 120 of the AK-X is provided at a cant angle p of 90° relative to main lifting portion 160 of the wing authority. To provide yaw authority, second trailing edge flap 150 is provided in winglet section 120. Fig. 3 also shows how the position of root airfoil 112 marks a boundary between main lifting section 160 of the wing, and outboard wing section or wing-tip device 100. In this particular design, root airfoil 112 is angled outboardly relative to the direction of flight DOF. With exception of the airfoil at the boundary between main lifting section 160 and root 110, and unless indicated otherwise, all airfoils referenced herein are defined parallel to the direction of flight DOF. A direction of lift DOL is perpendicular to direction of flight DOF and also represents the“upward” direction. Preferably, spanwise direction SW is perpendicular to both direction of flight DOF and direction of lift DOL.

[0026] SUMMARY

[0027] The presently disclosed technology is based on the surprising finding that winglets in particular for use in sailplanes can be improved using a trailing edge flap. Unless indicated otherwise, all definitions provided in the above “BACKGROUND” section also apply to the presently disclosed technology.

[0028] In one aspect, the disclosed technology pertains to a wing-tip device comprising a root having a root airfoil matching a wing airfoil of an outermost end of a lifting section of a wing; a winglet portion extending upwardly relative to the lifting section of the wing at a cant angle; a curved transition section connecting the root and the winglet portion; and a wing-tip device trailing edge flap comprising one or more flap segments.

[0029] In another aspect of the disclosed technology, there is provided an aircraft, preferably a sailplane, having any wing-tip device according to the disclosed technology. In some configurations, the aircraft, preferably sailplane, has a substantially tubular fuselage; a tail with horizontal and / or vertical stabilizers at an aft end of the fuselage; and a wing comprising any wing-tip device of the disclosed technology. There is also provided a wing for an aircraft, preferably sailplane, comprising any wing-tip device of the disclosed technology.

[0030] Preferably, the terms “sailplane” and “glider” are interchangeable. Preferably, a sailplane is to be understood as an airplane optimized for unpowered flight. More preferably, a sailplane is understood as an airplane designed for compliance with the Certification Specifications for Sailplanes and Powered Sailplanes CS-22 issued by the European Aviation Safety Agency and / or for compliance with Joint Aviation Requirements JAR-22 and / or for compliance with the acceptable means of compliance according to Advisory Circular 21.17-2A of the Federal Aviation Administration and / or comparable regulatory requirements. Within the applicable regulatory requirements, term “sailplane” does not rule out the presence of an auxiliary engine, either for self-launch or as a sustaining engine.

[0031] Alternatively or additionally, the sailplane has a maximum weight which does not exceed 850kg. Alternatively or additionally, the sailplane has a wing span of 30m or less, of 26m or less, of 25m or less, of 21 m or less, of 20m or less, of 18m or less, or of 15m or less. Alternatively or additionally, a maximum L / D of the sailplane or wing for the sailplane hasa maximum L / D at an airspeed in the range of 80 km / h to 150 km / h. The speed of maximum L / D can be referred to as best glide speed. Alternatively or additionally, the sailplane is a single-seat sailplane or a two-seat sailplane. Alternatively or additionally, the sailplane has a never exceed speed VNEof 350km / h or less, 330 km / h or less, 300km / h or less, or 280km / h or less.

[0032] In some configurations, the wing-tip device trailing edge flap is a camber changing flap. In other configurations, the wing-tip device trailing edge flap is a split flap, or a Fowler flap. In some configurations, the sailplane, wing and / or wing-tip device also comprises a leading edge flap, in particular any of the leading edge flaps as described in WO 2023 / 104323 A1 , the contents of which are incorporated herein by reference in their entirety.

[0033] Fixed-geometry winglets - i.e. winglets lacking a trailing edge flap such as shown in Fig. 1 - cannot adjust their camber in unison with the wing's flaps. This limitation restricts the aircraft's ability to optimize the spanwise circulation distribution across different flight conditions and speeds. Providing a trailing edge flap can also enable reduction in winglet surface area, further contributing to a reduction in drag.

[0034] In some configurations, the curved transition section rigidly connects the root and the winglet portion. In other words, the cantangle at which the winglet portion extends upwardly relative to the lifting section of the wing is a fixed cant angle. In some configurations, the wing-tip device lacks any means that would allow changing the cant angle, such as hinges, pivot joints, or the like.

[0035] In some configurations, the wing-tip device trailing edge flap extends in a spanwise direction from the root and at least partially into the curved transition section. In other words, contrary to for example the prior art configuration shown in Fig. 2, at least one of the one or more flap segments of the wing-tip device trailing edge flap is provided in the curved transition section. In some configurations, the wing-tip device trailing edge flap extends throughout the entire curved transition section and at least partially into the winglet portion.

[0036] In some configurations, the wing-tip device trailing edge flap comprises a single flap segment that extends from the root and at least partially into the curved transition section. In some configurations, the wing-tip device trailing edge flap comprises a single flap segment that extends from the root, throughout the curved transition section and at least partially into the winglet portion. Preferably, in such configurations, upper and / or lower surfaces of the single flap segment follow the curvature of the curved transition section.In some configurations, each of the one or more flap segments has a straight hinge segment. Preferably, the hinge segment comprises or provides a hinge axis which defines an axis of rotation for the respective flap segment. For a straight hinge segment, the hinge axis is also straight. Hinge segments can be provided in the form of rigid-body or elastic hinges. An exemplary elastic hinge is a film hinge. In some configurations, the one or more flap segments are connected to forward portions of the wing-tip device via a continuous flexible skin or a thin layer of elastomeric material that allows bending without the need for mechanical hinges.

[0037] In some configurations, the single flap segment comprises multiple straight hinge segments. In other configurations, a plurality of hinge segments are present, each comprising a straight hinge segment.

[0038] In some configurations, the wing-tip device trailing edge flap is configured to be passively slaved to a trailing edge flap of the lifting section of the wing. In other words, the wing-tip device trailing edge flap is caused to follow a deflection of the trailing edge flap of the lifting section of the wing. The slaving is passive, because no additional actuators are required to effect deflection of the wing-tip device trailing edge flap. In so far, the trailing edge flap of the lifting section of the wing can be considered the sole actuator of for the wing-tip device trailing edge flap. Such passive slaving is opposed to active slaving, in which an additional actuator - that is, an actuator separate from the trailing edge flap of the lifting section of the wing - is provided to effect deflection of the wing-tip device trailing edge flap, with the deflection being dependent on or in sync with that of the trailing edge flap of the lifting section of the wing. In other configurations of the wing-tip devices however, the slaving is active. In yet other configurations, the wing-tip device trailing edge flap is actively controlled using a separate actuator, but is not necessarily slaved to the trailing edge flap of the lifting section of the wing.

[0039] Separate actuators for control surfaces (used in but not limited to active slaving) such as trailing edge flaps are typically provided at least partially inside of the wing, that is they are at least partially enclosed by the wing’s outer surfaces. While effective, such separate actuators add weight, complexity, and maintenance requirements to the aircraft. For sailplanes and other aircraft, where minimal weight and mechanical simplicity are paramount, the added complexity of such systems can be a significant drawback. In some configurations however, active control such as active slaving can have certain benefits. Active control such as active slaving can for example allow advanced control capabilities.In some configurations of a passively slaved wing-tip device trailing edge flap, the wing-tip device lacks any active control means that would allow to directly affect rotation of the flap segments around their respective hinge segments. Alternatively or additionally, means for interconnecting the wing-tip device trailing edge flap with the trailing edge flap of the lifting section of the wing are provided. Preferably, such means transfer a deflection of the trailing edge flap of the lifting section of the wing to the wing-tip device trailing edge flap. Alternatively or additionally, the interconnection is removable. This is particularly beneficial in configurations in which the whole wing-tip device is removable from the wing. Mechanisms or means for passive slaving can also be referred to as trailing systems.

[0040] In some configurations, the one or more flap segments comprise an inboard flap segment and at least one adjacent outboard flap segment. Preferably, the outboard flap segment is passively slaved to the inboard flap segment, similar to what has been described above. In other words, the outboard flap segment is caused to follow a deflection of the inboard flap segment. For example, means for interconnecting the inboard flap segment to the outboard flap segment are provided. Preferably, such means transfer a deflection of the inboard flap segment to the outboard flap segment. Alternatively or additionally, an innermost flap segment, such as a flap segment forming a trailing edge of the root, is passively slaved to the trailing edge flap of the lifting section of the wing. A flap segment outboard from and directly adjacent to the innermost flap segment is passively slaved to the innermost flap segment. In such a way, all or a subset of flap segments can be slaved to a flap segment that is directly adjacent and inboard of the respective flap segment. Thereby, an inboard flap segment can serve as the actuator for the adjacent outboard flap segment.

[0041] In some configurations, there is a spanwise gap between the inboard flap segment and the adjacent outboard flap segment. This can be useful to prevent collisions of the inboard and outboard flap segments at different flap angles, in particular in the curved transition section. In other configurations, adjacent flap segments share a continuous upper and / or lower surface. Preferably, in place of gaps, deformable sections can be provided between adjacent flap segments to account for changes in flap angle in particular over the curved transition section.

[0042] In some configurations, the wing-tip device comprises at least one flap segment in each of the winglet portion and the curved transition section. Preferably, more than one flap segment is provided in the curved transition section. More preferably, three flap segments are provided in the curved transition section. In some configurations, a flap segment is provided in the root section.In some configurations, the wing-tip device comprises a continuous upper and / or lower surface extending in spanwise direction from the root to an outboard tip of the winglet portion. Preferably, this continuous upper and / or lower surface extends in chordwise direction from a leading edge of the wing-tip device to a flap gap separating the continuous upper and / or lower surface and the wing-tip device trailing edge flap. In some configurations, the flap gap is a recess in the upper and / or lower surface in an area in which the hinge segment is located. In some configurations, the hinge axis is located in the area of the flap gap. Preferably, the “chordwise” direction is defined by the chord line, that is the straight line in a plane defined by the direction of flight DOF and the direction of lift DOL which connects the leading edge and the trailing edge.

[0043] In some configurations, the continuous upper and / or lower surface extends in chordwise direction from the leading edge of the wing-tip device to the trailing edge of the wing-tip device, formed by the wing-tip device trailing edge flap. Preferably, in such configurations, there is no flap gap in chordwise direction separating a forward portion of the wing-tip device’s upper and / or lower surface and the wing-tip device trailing edge flap. Such gapless configurations can be achieved using e.g. flexible shells as known in the art.

[0044] Enabling passive camber adjustment of the winglet in coordination with the wing's control surfaces without relying on internal actuators can be beneficial for aerodynamic efficiency, might contribute to reduced weight and complexity, and might contribute to improved overall aircraft performance across various flight regimes.

[0045] Further and / or alternatively preferred configurations will be described in detail in the following together with the drawings listed below. The following description together with the drawings are therefore fully referenced for the purpose of detailing the previous description of the disclosed technology. It has to be understood that any of the individual features described in the following and / or shown in the drawings can be combined with, or replace corresponding features of any of the aspects and / or configurations described above. Moreover, it has to be understood that the fact that a certain feature is recited by an independent claim and / or the description of any of the aspects or configurations, is not sufficient to indicate whether the feature is an essential feature. The applicant reserves the right to change the claimed scope to be broader than originally filed, and to file divisional applications directed at subject-matter other than that of the originally filed claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In the following, further aspects, implementations and examples of the disclosed technology are described in conjunction with the attached drawings. The skilled reader will immediately recognize that the attached drawings are derived from CAD (computer-aided design) models, and as such, are to scale. The combinations of absolute and relative dimensions reproduced in the attached drawings are representative of the depicted particular aspects, implementations and examples, and as such are not limiting or essential for the disclosed technology.

[0047] Fig. 1 shows an exemplary prior art outboard wing section comprising a winglet;

[0048] Fig. 2 shows a further exemplary prior art outboard wing section comprising a winglet;

[0049] Fig. 3 shows a prior art tailless glider, in particular the Akaflieg Karlsruhe AK-X;

[0050] Fig. 4 shows an exemplary wing-tip device 400 according to the disclosed technology, the configuration of which is generally similarto the prior art configurations shown in Figs. 1 and 2;

[0051] Fig. 5a shows a further exemplary implementation of a wing-tip device 500 according to the disclosed technology;

[0052] Fig. 5b is a bottom view of a detail of wing-tip device 500 shown in Fig. 5a;

[0053] Fig. 6a illustrates another configuration of a wing-tip device 600 that is generally similar to those of Figs. 4, 5a and 5b in a frontal view opposite to direction of flight DOF;

[0054] Fig. 6b is a view of wing-tip device 600 shown in Fig. 6a roughly outwardly along spanwise direction SW;

[0055] Fig. 7a shows a detail view of a wing-side portion of an exemplary passive slaving I trailing mechanism for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing;

[0056] Fig. 7b shows a wing-tip device side portion of a passive slaving I trailing mechanism for connection with the wing of Fig. 7a;Fig. 8a shows a detail view of a wing-side portion of another exemplary passive slaving I trailing mechanism for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing;

[0057] Fig. 8b shows a wing-tip device side portion of a passive slaving I trailing mechanism for connection with the wing of Fig. 8a;

[0058] Fig. 9 is an isometric view of a sailplane according to the disclosed technology.

[0059] DETAILED DESCRIPTION OF SPECIFIC EXAMPLES

[0060] In the following sections, further aspects, implementations and examples of the disclosed technology are described in conjunction with the attached drawings. Titles are provided for each of the following sections to enhance readability. The titles are not intended to be limiting for the disclosed technology. It is understood from the technical content of the following description that aspects, implementations and examples described in different sections are readily combinable, even where such a combination is not explicitly mentioned. Moreover, even though some elements are shown in combination in the attached drawings, these elements can generally also be present isolated from one another in other implementations. Insofarthe following description suggests a link between different elements shown in combination in the attached drawings, such link is not to be considered inextricable unless an indispensable technical requirement exists for such a combination.

[0061] Wing-tip device

[0062] Specific aspects and configurations of wing-tip devices according to the disclosed technology are detailed hereafter with reference to Figures 4-6b. As will become clearer from the following description, the wing-tip devices are not limited to the specific examples depicted in Figures 4-6b. In particular, it is not necessary that wing-tip devices according to the disclosed technology comprise all features depicted in or described in conjunction with Figures 4-6b, or that such elements - if present - are provided in the exact configuration and / or dimensions depicted in or described in conjunction with Figures 4-6b. Any disclosure in the context of Figures 4-6b also applies to all wing-tip devices, wings, and aircraft of the disclosed technology.

[0063] Fig. 4 shows an exemplary wing-tip device 400 according to the disclosed technology, the configuration of which is generally similar to the prior art configurations shown in Figs. 1 and 2. As such, wing-tip device 400 comprises a root 410 having a root airfoil 412 matchinga wing airfoil of an outermost end of a lifting section of a wing (not shown), to which wingtip device 400 can be attached. Wing-tip device 400 further comprises a winglet portion 420 extending upwardly relative to the lifting section of the wing at a cant angle p, which can be measured relative to spanwise direction SW as shown. Winglet portion 420 and root 410 are connected by a curved transition section 430. Transition section 430 is curved in that it provides a smooth or kink-free transition between root 410 which extends in spanwise direction SW, and winglet portion 420 that extends out of plane of root 410 at cant angle p.

[0064] Wing-tip device 400 differs from the prior art configurations of Figs. 1 and 2 in that a wingtip device trailing edge flap 440 comprising one or more flap segments 442, 444, 446a-c is provided, with wing-tip device trailing edge flap 440 extending in spanwise direction SW from root 410, throughout curved transition section 430 and at least partially into winglet portion 420. That is, contrary to the prior art configurations of Figs. 1 and 2, trailing edge flap segments 446a-c are provided throughout curved transition 430, in the depicted configuration three flap segments 446a-c. As such, contrary to the prior art configurations of Figs. 1 and 2, curved transition section 430 has no fixed-geometry airfoil. Instead, by virtue of trailing edge flap segments 446a-c, a camber of curved transition section 430 can be changed.

[0065] Each of flap segments 442, 444, 446a-c has a corresponding straight hinge segment providing a hinge axis AX1 , AX2, AX3a-c, which defines an axis of rotation for the respective flap segment. In this configuration, the hinge segments are configured as rigid-body hinges, such as in the form of a hinge having a knuckle or sleeve and a pin or rod. As a rigid-body hinge, hinges are to be understood, in which movement of two components linked by the hinge causes elements in the hinge to move relative to each other as rigid bodies, without deformation of hinge elements making any significant contribution to the hinge’s range of motion. Rigid-body hinges thus involve some degree of surfaces of hinge components sliding or rolling with respect to each other. Typical examples of rigid-body hinges are rolling bearings and plain bearings.

[0066] Further or alternative features of wing-tip device 400 are described with reference to the wing-tip devices of Figs. 5a-6b.

[0067] Fig. 5a shows a further exemplary implementation of a wing-tip device 500 according to the disclosed technology. For the sake of visual clarity, not all components of wing-tip device 500 are labelled with reference signs. However, their presence and function can beclearly inferred from Fig. 5a, particularly taking into account the preceding description relating to Fig. 4.

[0068] Fig. 5a particularly illustrates how root 510 can be configured for removably connecting wing-tip device 500 to the lifting section of the wing. For this purpose, connection means are provided. Such connection means are commonly used in sailplane design for providing removable wing-tip devices. In the illustrated configuration, the connection means comprise a tube 516 and a pin 518 extending inwardly in spanwise direction from a root rib 514. Other connection means for this purpose are well known and can also be used. In other configurations of the disclosed technology, the wing-tip device is permanently attached to the wing, and / or an integral part of the wing structure.

[0069] Fig. 5b is a bottom view of a detail of wing-tip device 500 shown in Fig. 5a. Fig. 5b illustrates some exemplary configurations of flap segments 542, 544, 546a-b. In the depicted configuration, at least some of flap segments 542, 544, 546a-b comprises a respective elastic hinge in the form of a film hinge. For example, root flap segment 542 has a straight hinge segment 543, inboard transition section flap segment 546a has a straight hinge segment 547a, and outboard transition section flap segment 546b has a straight hinge segment 547b. In the depicted configuration, hinge segments 543, 547a and 547b are provided as recessed portions of a skin or shell forming an outer aerodynamic surface of wing-tip device 500. Recessing portions of a skin or shell of wing-tip device 500 creates localized reductions in thickness, and thus bending stiffness. The recessed portions can thus act as film hinges, which enable rotation of flap segments 542, 544, 546a-b by elastic deformation of hinge segments 543, 547a and 547b.

[0070] Dashed lines in Figs. 5a and 5b represent preferred positions for boundaries between root 510, transition section 530 and winglet portion 520.

[0071] Fig. 5b also illustrates how adjacent flap-segments can be separated in spanwise direction by gaps 549, which serve to prevent collisions when deflecting wing-tip device trailing edge flap 540. Contrary to hinge segments 543, 547a and 547b, gaps 549 of the depicted configurations are cuts that extend through the entire thickness of flap segments 542, 544, 546a-b.

[0072] Different from Fig. 4, wing-tip device 500 of Figs. 5a and 5b has two transition section flap segments 546a-b, even though any other number of flap segments can be present in the transition section. Hinge section 545 of winglet section flap segment 544 of wing-tipdevice 500 can comprise a rigid body hinge, similar to wing-tip device 400, or a film hinge similar to hinge segments 543, 547a and 547b.

[0073] Figs. 6a and 6b illustrate another configuration of a wing-tip device 600 that is generally similar to those of Figs. 4, 5a and 5b. Fig. 6a is a frontal view opposite to direction of flight DOF and particularly illustrates curvature of leading edge 632 in transition section 630. In this and some other preferred configurations, leading edge 632 throughout winglet section 620 is substantially straight when viewed in this plane. A dashed line in Fig. 6a marks an exemplary position for the boundary between transition section 630 and winglet section 620.

[0074] In other configurations, the wing-tip device 600 lacks any notable straight winglet portion outboard of curved transition section 630. Such configurations are known for example from the winglets of the Rolladen-Schneider LS-8-18 sailplane. In some of these configurations, the wing-tip device of the disclosed technology may comprise a root and a curved section extending from the root up to an outboard tip of the wing-tip device. In some of these configurations, it might not be meaningful to define a cant angle, or the cant angle could be defined as the angle between the lifting section and a line connecting an inboard start of the transition section with the outboard tip of the wing-tip device. In some of these configurations, the wing-tip device trailing edge flap only extends partially into the curved section. In other words, it is not necessary that the wing-tip device trailing edge flap extends throughout the entire curved section. In other such embodiments, however, the wing-tip device trailing edge flap extends throughout the entire curved section.

[0075] Wing-tip device 600 of Figs. 6a and 6b particularly differ from those of Figs. 4, 5a and 5b in that root 610 lacks any notable straight spanwise extension of the main lifting section of the wing. That is, transition section 630 begins immediately at root profile 612. In other configurations however, root 610 comprises an extension portion 613 (indicated in dashed lines in Fig. 6a) that constitutes a spanwise extension of the main lifting section, in particular an extension thereof in which the leading edge is substantially straight when viewed in a plane perpendicular to direction of flight DOF.

[0076] Figs. 6a and 6b also show a spar stump 616 as an exemplary means for connecting wingtip device 600 to the main lifting section of the wing.

[0077] Fig. 6b is a view roughly outwardly along spanwise direction SW and details in particular transition section 630 of wing-tip device 600 with transition section flap segments 646a-cand their respective hinge portions 647a-c. In this configuration, at least the two inboard hinge portions 647a and 647b are configured as film hinges. In this particular configuration, at least for the two inboard hinge portions 647a and 647b, at least one of an upper shell 662 and a lower shell 664 (preferably a fiber reinforced composite shell, such as GFRP - glass fiber reinforced plastic - or CFRP - carbon fiber reinforced plastic) of a section 660 forward of wing-tip device trailing edge flap 640 continuously extends in chordwise direction throughout hinge portions 647a and 647b into flap segments 646a, 646b to form respective upper and or lower shells 666a, b; 668a, b thereof.

[0078] Fig. 6b also illustrates an exemplary configuration for passively slaving flap segments to a respective inboardly adjacent flap segment and / or to passively slave entire wing-tip device trailing edge flap 640 to a trailing edge flap of the main lifting section of the wing. For example, innermost flap segment 646a comprises a sleeve 670a extending substantially in spanwise direction in a space between upper and lower shells 666a, 668b. Sleeve 670a is configured to slidingly receive a pin (not depicted for illustrative clarity) extending in spanwise direction from the trailing edge flap of the main lifting section of the wing, to passively transfer deflection of the trailing edge flap of the main lifting section of the wing to innermost flap segment 646a. Similarly, flap segment 646b immediately outboard of innermost flap segment 646a can comprise a corresponding sleeve 670b configured to slidingly receive a pin (not depicted for illustrative clarity) extending in spanwise direction from innermost flap segment 646a, so as to passively transfer deflection of innermost flap segment 646a to flap segment 646b. By the same principle, a sleeve 670c in flap segment 646c immediately outboard of flap segment 646b can be employed to passively slave flap segment 646c to its inboard neighbor, flap segment 646b. In some configurations, each offlap segments 646a-c has a separate pin for coupling to a sleeve of its immediate outboard neighbor. Sliding of these pins within sleeves 670a-c is necessary to account for changes in the width of spanwise gaps 649 at different flap angles. In other configurations, a continuous wire can extend through two or more of sleeves 670a-c. Such configurations may benefit from some bending flexibility of the wire to account for the curvature of transition section 630.

[0079] Gaps 649 and all other gaps between adjacent flap segments and / or between a trailing edge flap and a forward section of any of the wing-tip devices disclosed herein can preferably be covered with suitable flap seals, as is commonly known in the art of sailplane design for covering flap gaps.Further passive slaving / trailing mechanisms

[0080] Specific aspects and implementations of further passive slaving / trailing mechanisms for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing are detailed hereafter with reference to Figures 7a-8b. As will become clearer from the following description, such mechanisms are not limited to the specific examples depicted in Figures 7a-8b. Any disclosure in the context of Figures 7a-8b also applies to all wing-tip devices, wings, and aircraft (such as sailplanes) of the disclosed technology. Moreover, while primarily described as mechanisms for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing, these mechanisms can also be employed as mechanisms for slaving individual flap segments of a wing-tip device trailing edge flap to one another.

[0081] Figs. 7a and 7b show an exemplary passive slaving I trailing mechanisms for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing.

[0082] The respective wing-side elements of this mechanism are depicted in Fig. 7a, which shows a detail view of an outermost end of a main lifting section 710 of a wing 700, with a trailing edge flap 720. In this configuration, a key or protrusion 722 extends in spanwise direction from an outermost end of trailing edge flap 720. Fig. 7a also shows flexible tape 730 as means to seal a gap between trailing edge flap 720 and a forward section 712 of wing 700.

[0083] Fig. 7b shows a detail view of respective wing-tip device side elements for this slaving mechanism. In particular, Fig. 7b illustrates an inboard end of wing tip device 800 with wingtip device trailing edge flap 840 comprising a slot 842 configured to slidingly receive key or protrusion 722 of main lifting section trailing edge flap 720, when wing-tip device 800 is attached to wing 700. Fig. 7b also demonstrates the use of flexible tape 730 to seal a flap gap.

[0084] In other configurations, wing-tip device trailing edge flap 840 can be provided with a key or protrusion while a corresponding slot is provided in main lifting section trailing edge flap 720.

[0085] Figs. 8a and 8b show another exemplary passive slaving / trailing mechanisms for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing.Fig. 8a provides a view of the wing-side elements of the mechanism. Here, trailing edge flap 920 of wing 900 comprises a protrusion 922 that is a spanwise extension of the bottom skin or shell of trailing edge flap 920. As can be seen in Fig. 8b, wing-tip device 1000 in its wing-tip device trailing edge flap 1040 has a corresponding recess 1042 in its bottom skin or shell. When wing-tip device 1000 is attached to wing 900, protrusion 922 extends into recess 1042 such that the protrusion’s upper surface contacts the recess lower surface. Upward deflection of trailing edge flap 920 is transferred to wing-tip device trailing edge flap 1040 by the upper surface of the protrusion 922 pushing against the lower surface of recess 1042. Downward deflection of trailing edge flap 920 is passively followed by wingtip device trailing edge flap 1040 by virtue of a flap moment biasing wing-tip device trailing edge flap 1040 towards downward deflection.

[0086] Other passive slaving I trailing mechanisms for passively slaving a wing-tip device trailing edge flap to a trailing edge flap of a main lifting section of a wing can be used with the disclosed technology, many of which are readily known from the prior art.

[0087] Sailplane

[0088] Specific aspects and configurations of sailplanes according to the disclosed technology are detailed hereafter with reference to Figure 9. As will become clearer from the following description, the sailplanes are not limited to the specific example depicted in Figure 9. In particular, it is not necessary that sailplanes according to the disclosed technology comprise all features depicted in or described in conjunction with Figures 9, or that such elements - if present - are provided in the exact configuration and / or dimensions depicted in or described in conjunction with Figure 9. Any disclosure in the context of Figures 9 also applies to all wing-tip devices, wings, and aircraft of the disclosed technology.

[0089] Fig. 9 shows a sailplane 1200 having a pair of wing-tip devices 1210a, 1210b according to the disclosed technology, with one wing-tip device 1210a, 1210b per wing 1220a, 1220b. Wing-tip devices 1210a, 1210b can be any wing-tip device of the disclosed technology described herein. Wings 1220a, 1220b each comprise respective wing-tip device 1210a, 1210b, and a respective main lifting section 1222a, 1222b. Wing-tip device root airfoils 1212a, 1212b mark a boundary between wing-tip devices 1210a, 1210b and respective main lifting sections 1222a, 1222b, similar to what was described with reference to Fig. 3.

[0090] Main lifting sections 1222a, 1222b comprise respective trailing edge flaps 1223a, 1223b. In some configurations, the wing-tip device trailing edge flaps are passively slaved torespective trailing edge flaps 1223a, 1223b, such as in any of the ways described elsewhere herein.

[0091] Each main lifting section 1222a, 1222b extends from fuselage 1230 at a respective wing root 1224b to an outboard or outermost end at which a wing airfoil matches root airfoil 1212a. 1212b of wing-tip device 1210a, 1210b. In Fig. 9, the wing root is only visible for wing 1220b, with the wing root of wing 1220a being obstructed from view by fuselage 1230. In the depicted configuration, the sailplane is of a mid-wing design. In other configurations, the sailplane is of a shoulder-wing design, similar to the Jonkers JS3, or of a high-wing design, similar to the Akaflieg Mlinchen Mii31 .

[0092] Wings 1220a, 1220b are typically removable from the fuselage 1230, as is known in the art of sailplane design, e.g. at the wing roots. Thus, wings 1220a, 1220b can exist independently of the fuselage.

[0093] In the depicted configuration, sailplane 1200 has a wingspan of about 18m. In other configurations, the sailplane can have a wing span of about 30m (or less), of about 26m (or less), of about 25m (or less), of about 21m (or less), of about 20m (or less), of about 18m (or less), of about 15m (or less), or of about 13.5m (or less).

[0094] In the depicted configuration, sailplane 1200 has a conventional tail or empennage 1240 with a horizontal stabilizer 1242 and a vertical stabilizer 1244. Particularly, in the depicted configuration, tail 1240 is a T-tail. That is, horizontal stabilizer 1242 is disposed on top of vertical stabilizer 1244. In other configurations, sailplane 1200 has a conventional tail 1240 with a horizontal stabilizer 1242 and a vertical stabilizer 1244 in another arrangement, such as in a cruciform configuration or in a fuselage mounted configuration. In yet other configurations, sailplane 1200 is tailless, such as shown in Fig. 3.

[0095] In the depicted configuration, sailplane 1200 is a single-seater. In other configurations, sailplane 1200 is a double-seater. In such configurations, the seats can be arranged in tandem (such as in an Alexander Schleicher ASK-21) or in a side-by-side configuration (such as in a Stemme S10).

[0096] Sailplane 1200 can also comprise an engine, such as a sustainer engine or an engine capable of self-launching the sailplane. The engine can an electric engine, or an internal combustion engine. It can be a turbine or a reciprocating engine or a rotary engine. In some configurations, the engine can drive a propeller. The engine and / or propeller can beretractable, such as is known in the art with retractable engines positioned in an engine bay aft of cockpit 1230. In other configurations, the engine and / or propeller is retractable and positioned in front of cockpit 1230 (such as in a Stemme S10). In other configurations, at least the propeller is not fully retractable, but e.g. folds onto the sides of the fuselage as is known from the Front Electric Sustainer- FES concept.

Claims

CLAIMS1. Sailplane having a wing and a wing-tip device provided at an outermost end of a lifting section of the wing, the wing-tip device comprising:a root having a root airfoil matching a wing airfoil of the outermost end of the lifting section of the wing;a winglet portion extending upwardly relative to the lifting section of the wing at a cant angle;a curved transition section rigidly connecting the root and the winglet portion; and a wing-tip device trailing edge flap comprising one or more flap segments; wherein the wing-tip device trailing edge flap extends in a spanwise direction from the root and at least partially into the curved transition section;preferably wherein the wing-tip device trailing edge flap extends throughout the entire curved transition section and at least partially into the winglet portion.

2. Sailplane of claim 1 , wherein each of the one or more flap segments has a straight hinge segment.

3. Sailplane of any one of the preceding claims, wherein the wing-tip device trailing edge flap is configured to be passively slaved to a trailing edge flap of the lifting section of the wing.

4. Sailplane of any one of the preceding claims, wherein the one or more flap segments comprise an inboard flap segment and at least one adjacent outboard flap segment.

5. Sailplane of claim 4, wherein the outboard flap segment is passively slaved to the inboard flap segment.

6. Sailplane of any one of claims 4 or 5, comprising a chordwise gap between the inboard flap segment and the outboard flap segment.

7. Sailplane of any one of the preceding claims, comprising at least one flap segment in each of the winglet portion and curved transition section.

8. Sailplane of any one of the preceding claims, comprising a continuous upper surface extending in spanwise direction from the root to an outboard tip of the winglet portion.

9. Sailplane of claim 8, wherein the continuous upper surface extends in chordwise direction from a leading edge of the wing-tip device to a flap gap separating the continuous upper surface and the wing-tip device trailing edge flap.

10. Sailplane of any one of the preceding claims, comprising a continuous lower surface extending in spanwise direction from the root to an outboard tip of the winglet portion.

11. Sailplane, wherein the continuous lower surface extends in chordwise direction from a leading edge of the wing-tip device to a flap gap separating the continuous lower surface and the wing-tip device trailing edge flap.

12. Sailplane of any one of the preceding claims, wherein the wing-tip device trailing edge flap is a camber changing flap.

13. Sailplane of any one of the preceding claims, wherein the root comprises connection means for removably connecting the wing-tip device to the lifting section of the wing.

14. Wing for a sailplane as defined in any one of claims 1 to 13.

15. Wing-tip device for a sailplane as defined in any one of claims 1 to 13.

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