WO2023043313A1

WO2023043313A1 - Actuation device for actuating a high-lift device of a rotor blade

Info

Publication number: WO2023043313A1
Application number: PCT/NL2022/050522
Authority: WO
Inventors: Yasir ZAHOOR; Roeland De Breuker; Jurij SODJA; Mark VOSKUIJL
Original assignee: Technische Universiteit Delft
Priority date: 2021-09-17
Filing date: 2022-09-16
Publication date: 2023-03-23
Also published as: NL2029203B1

Abstract

Actuation device for a high-lift device of a rotor blade, comprising a first link, movable in a span- wise direction, outwardly by a centrifugal force, a biasing member, connected with the first link and configured to exert an opposite force thereon, so as to bias the first link inwardly in the span- wise direction, a second link, movable in a chord-wise direction and coupled with the high-lift device, and a translation member, coupled with the first link and the second link, wherein the translation member is movable by the first link in the span-wise direction, wherein the second link comprises an engagement end, engaged with the translation member, and an actuation end, coupled with the high-lift device, and the translation member comprises a guiding element, engaged with the engagement end, wherein the guiding element guides the second link in the chord-wise direction upon movement of the first link along the span-wise direction.

Description

ACTUATION DEVICE FOR ACTUATING A HIGH-LIFT DEVICE OF A ROTOR BLADE

The present application relates to an actuation device for actuating a high-lift device of a rotor blade, as well as a rotor blade comprising said actuation device, a rotor comprising said rotor blade, and an aircraft comprising said rotor.

Rotorcraft, such as helicopters, utilize rotors to produce aerodynamic lift forces. Such rotors may be used as a main lift generating system for a rotorcraft, or for countering the reactional torque of the main rotor on the fuselage of the rotorcraft (e.g., as a tail rotor), or the like. Fixed-wing aircraft may also use rotors for propulsion, which are generally referred to as propellers or airscrews. In the present disclosure, propellers and rotors will be generally referred to as rotors. Accordingly, concepts illustrated by means of rotors for rotorcraft may also apply to propellers for fixed-wing aircraft. In addition, the same principles may be applied to other relevant technical fields in which rotors are applied, such as wind turbines, propellers for marine applications, propellers for other types of aircraft, such as airships, et cetera.

Generally, a rotor comprises a number of rotary wings, which are hereinafter referred to as rotor blades. As well known in the art, rotor blades may generally be described as elongate airfoils. A rotor is formed by mounting one or more rotor blades to a central rotating mast. The rotating mast is driven in order to rotate the rotor blades around a common center point, thereby providing lift forces due to the downward displacement of air by means of the quickly rotating elongate airfoils, i.e., rotor blades.

Rotor blades may comprise so-called active components, which alter the aerodynamic characteristics thereof. For instance, the rotor blades may be mounted on a pitch hinge, or the like, to alter their pitch angle, i.e., to allow the rotor blades to be rotated about their longitudinal axes. In addition, rotor blades may (additionally) comprise high-lift devices, such as flaps and/or slats, in order to actively alter their airfoil, in particular the camber and/or chord length thereof. Active components, in particular high-lift devices, may significantly increase the complexity of rotor blades, but may provide advantages, such as increased lift, or the like.

Variable-speed rotorcraft may be capable of altering the rotational speed of their rotor(s) during flight. Changing the rotation speed of a rotor also changes the generated lift force. For example, lowering the rotation speed of a rotor generally decreases the amount of lift force that is generated, if no changes are made to the rotor’s configuration. Accordingly, variable-speed rotorcraft may benefit from active components, such as the ones described earlier. For instance, variable-speed rotorcraft may be equipped with rotor blades with adjustable pitch. Increasing the pitch of a rotor blade may increase the angle of attack of the rotor blade, and may thereby increase the amount of lift generated by the rotor blade. The pitch angle may be controlled by a pilot through a collective (also referred to as collective lever), such as those used in helicopters. Alternatively or additionally, high-lift devices, such as trailing edge flaps, may be used on rotor blades in order to (partially) replace or reduce the required controllable pitch angle range of the rotor blade.

For example, patent document US 5 570 859 A describes a spoiler flap that is pivotably mounted to the rearward portion of a wind turbine blade or wing to control or influence air flow over the surface of the blade or wing. The spoiler flap has forward and rearward edges. The spoiler flap can be pivoted to simultaneously raise the forward edge, into low pressure flow, and lower the rearward edge of the spoiler flap, into high pressure flow. The extent to which the spoiler flap is pivoted determines the extent to which the air flow over the surface of the blade or wing is influenced.

For example, patent document GB 800 890 A describes a rotary wing aircraft having two loadcarrying rotors rotatable in opposite directions at a predetermined speed ratio relative to one another and having rotor blades of airfoil contour, and further comprising means for controlling the directional heading of the aircraft having aerodynamic brakes at the tips of the blades of the rotors and means for selectively actuating such brakes to create a reaction torque differential tending to turn the aircraft about a vertical axis.

A disadvantage of high-lift devices on rotor blades is increased complexity in control and maintenance. Accordingly, manufacturing and maintenance costs of rotor blades for rotorcraft (or propellers for fixed-wing aircraft) which utilize high-lift devices are increased. In addition, the complexity of the control mechanism of the rotorcraft is increased as well.

It is an object of the present disclosure, amongst other objectives, to provide a rotor blade which mitigates or alleviates at least part of the aforementioned disadvantages.

For this purpose, according to a first aspect of the present disclosure, an actuation device for actuating a high-lift device of a rotor blade is provided, comprising a first link, movable in a substantially span-wise direction of the rotor blade, and outwardly in the substantially span-wise direction by a centrifugal force generated by rotation of the rotor blade, a biasing member, connected with the first link and configured to exert an opposite force thereon, opposite the centrifugal force, so as to bias the first link inwardly in the substantially span-wise direction, a second link, movable in a substantially chord-wise direction of the rotor blade and configured to be coupled with the high-lift device, and a translation member, coupled with the first link and the second link, wherein the translation member is configured to be movable by movement of the first link in the substantially span-wise direction, thereby effecting movement of the second link in the substantially chord-wise direction, so as to actuate the high-lift device, wherein the second link comprises an engagement end, engaged with the translation member, and an actuation end, configured to be coupled with the high-lift device, and the translation member comprises a guiding element, engaged with the engagement end of the second link, wherein the guiding element is configured to guide the second link in the substantially chord-wise direction upon movement of the first link along the substantially span-wise direction.

The actuation device according to the first aspect of the present disclosure is capable of passively actuating a high lift device. For instance, the actuation device may passively control the flap angle of a trailing-edge flap of a rotor blade. Specifically, the first link is movable along a span-wise direction of the rotor blade, preferably corresponding to a direction of a centrifugal force generated during use of the rotor blade, by means of the centrifugal force experienced by the rotor blade upon rotation thereof. In other words, with increasing rotation speed of the rotor, the first link moves further outwards, in the span- wise direction. With lower rotational speeds, the opposite force generated by the biasing member may (partially) overcome the centrifugal force, such that the first link moves inwardly in the span-wise direction. Accordingly, the first link and the biasing member provide proportional actuation on the basis of centrifugal force, i.e., on the basis of the rotational speed of the rotor. High-lift devices, such as trailing-edge flaps or leading-edge slats, generally require actuation in a chord- wise direction of the rotor blade, which is provided by the second link according to the present actuation device. In order to actuate the second link on the basis of the proportional actuation provided by the first link, a translation member is provided, which essentially transforms a span-wise movement to a chord-wise movement. In particular, the translation member is engaged with the first link, and movable thereby, and is in turn engaged with the second link, in order to move the second link based on the movement of the first link. Finally, by movement of the second link, which is couplable with a high-lift device, such as a trailing-edge flap, the high-lift device is actuated. Hence, the actuation device according to the first aspect of the present disclosure does not require active control components, thereby reducing the mechanical complexity of both the control system of the rotorcraft and the rotor blade, and in turn lowering the manufacturing and maintenance costs of both. In an exemplary embodiment of the actuation device, the high-lift device is a trailing-edge flap. For example, the biasing member may be designed such that at maximum rotational speed of a rotor, the first link is allowed to be extended to its furthest outward position in the span-wise direction, and the second link is configured such that the furthest outward position of the first link translates to a fully stowed position of the trailing-edge flap. For instance, the biasing member may further be designed such that at a threshold rotational speed of a rotor, being lower than the maximum rotational speed, the first link is allowed to be at its resting position, i.e., its furthest inward position, and the second link and/or the translation member is configured such that the furthest inward position of the first link translates to a fully deployed position of the trailing-edge flap. The threshold rotational speed of a rotor may for instance be 90% of the maximum rotational speed. The high-lift device may also be actuated to be somewhere between its fully stowed position and its fully deployed position. For instance, a trailing-edge flap may be controlled between 0° and 30° of rotation, or the like, wherein 0° may correspond to the fully stowed position and 30° may correspond to the fully deployed position.

Preferably, the substantially span- wise direction is substantially orthogonal to the substantially chord-wise direction. The span-wise direction preferably corresponds to the direction of centrifugal force generated by rotation of the rotor blade (about a rotation axis of the rotor), such that the first link is (substantially) in line with the centrifugal force. The span-wise direction may correspond, substantially, with a longitudinal axis of the rotor blade. The chord-wise direction preferably corresponds to a direction substantially orthogonal to the centrifugal force, and may correspond to a direction perpendicular to a longitudinal axis of the rotor blade, i.e., a transverse direction of the rotor blade.

It is preferred that the translation member is fixed (i.e., rigidly connected) to the first link, such that the translation member is movable in the substantially span-wise direction simultaneously with the first link. The translation member may in this case further provide additional weight to the first link, thereby increasing the centrifugal force acting on the first link and the translation member. Accordingly, the actuation effort, in order to move the second link, is effectively reduced. Preferably, the translation member is manufactured of a metal. Metals may have a relatively high specific weight, i.e., density, such that sufficient weight for purposes of the generation of centrifugal force may be comprised in a relatively small volume. Alternatively, the translation member may be manufactured of a different material, such as a plastic, a composite, a resin, or the like. It is further preferred that the guiding element comprises a guiding surface, configured to guide the engagement end of the second link, wherein the guiding surface defines a guiding path which lies substantially in a movement plane, defined by the substantially chord-wise and substantially spanwise directions (and/or defined by the first and second links). Preferably, the guiding path is a sloped guiding path, which is sloped with respect to the substantially span-wise direction. The sloped guiding path may be linear, or non-linear (e.g., curved). For instance, the translation member may have a wedge shape or a double wedge shape (e.g., a triangular shape), thus defining at least one sloped surface, against which the engagement end of the second link is engaged. Accordingly, upon movement of the first link in the span-wise direction, the sloped surface of the guiding element of the translation member forces the second link away from or toward the first link, as the engagement end of the second link remains in contact with the sloped guiding surface. Preferably, the movement of the second link is restricted such that it is only linearly movable, e.g., in the chord-wise direction. Accordingly, the sloped guiding surface enforces a certain distance between the first link and the second link, thereby actuating the high-lift device on the basis of movement of the first link.

It is further preferred that the guiding element comprises a guiding groove, which includes the guiding surface, wherein the engagement end of the second link is coupled with the guiding groove. Providing the guiding surface in a guiding groove further ensures movement of the second link in the movement plane, preventing out-of-plane movement of the second link (e.g., perpendicular to the movement plane), and specifically the engagement end of the second link. Accordingly, vibrations of the rotor blade affect the actuation of the high-lift surface to a lesser extent. The guiding groove may further comprise a retention element, which is configured to retain the engagement end of the second link in the guiding groove. For example, the guiding groove may comprise a base, formed by the guiding surface, and two sidewalls extending perpendicularly from the base. Additionally, for example, the guiding groove may comprise the retention element in the form of two retention plates, extending towards each other, perpendicularly from the two sidewalls as seen in cross-section of the guiding groove, wherein the free longitudinal edges of the retention plates thus face each other. In other words, for example, as seen in cross-section, the guiding groove is substantially U-shaped and the retention plates extend inwards from the two ends of the legs of the U-shaped guiding groove. The engagement end of the second link may then be formed such that the distal end of the engagement end is securely retained within the guiding groove. For example, the engagement end may be formed as a ball joint or the like.

It is further preferred that the engagement end of the second link is engaged with the guiding surface by means of a bearing, preferably a roller bearing. The bearing ensures low-resistance movement of the engagement end of the second link on the guiding surface of the translation member and/or through the guiding groove. For instance, in the above example of the guiding groove with the retention element, a roller bearing of the engagement end may engage with the base (formed by guiding surface) and the retention element(s), such that low-resistance movement of the engagement end of the second link within the guiding groove is ensured, regardless of whether the second link is extended or retracted in chord-wise direction.

It is further preferred that the biasing member is a spring. The spring may be an extension spring or a compression spring. The biasing member is preferably connected to a free end of the first link, and an anchor point. The anchor point may for instance be formed by a housing of the actuation device or by the rotor blade. As described above, the biasing member provides a force opposite the centrifugal force generated by the rotating rotor blade. The biasing member preferably generates an opposite force proportional to the position of the first link with respect to its resting position (i.e., its most inwardly position in the span-wise direction). In the case that the biasing member is a spring, the opposite force, opposite the centrifugal force, generated by the spring and applied to the first link, is preferably proportional to the extension of the spring (or compression of the spring, in case of a compression spring). The spring may, for instance, provide an opposite force following Hook’s law, in case the spring is not extended or compressed beyond its elastic limit, wherein Hook’s law is defined by F = — k ■ x, wherein F is the opposite force, k is the spring constant, and x is the distance over which the spring is extended (or compressed). Preferably, the characteristics of the biasing member, e.g., initial tension and stiffness of the spring, are chosen such that up to a minimum threshold rotational speed of the rotor blade, the first link is kept in its resting position. Preferably, the characteristics of the biasing member, e.g., initial tension and stiffness of the spring, are chosen such that above the minimum threshold rotational speed of the rotor blade, the first link moves from its resting position, outwardly in the substantially span-wise direction. The maximum outward position of the first link may be reached upon reaching a maximum threshold rotational speed of the rotor blade, which may be equal to the actual maximum rotational speed of the rotor blade, or another rotational speed higher than the minimum threshold rotational speed. The maximum outward position and/or minimum outward position of the first link may be enforced by a stopping member, configured to restrict movement of the first link beyond a certain point, or the opposite force generated by the biasing member, or both. For instance, the stopping member may be formed by a guide or support of the first link, configured to guide and/or support the first link. Alternatively, the biasing member may be a friction member, providing resistance against movement outwardly in the span- wise direction, or a piston member, pulling a vacuum upon movement of the first link outwardly in the span-wise direction, a magnetic element, a resistance pulley, an elastic member, or the like. It is further preferred that the first link and/or the second link is an elongate shaft. Preferably, the elongate shaft is constrained by supports, allowing movement of the elongate shaft in longitudinal direction thereof and supporting the elongate shaft, preferably wherein the supports are bearing supports. Preferably, movement of the elongate shaft is only allowed in longitudinal direction, such that the actuation of the high-lift device is relatively undisturbed by vibrations of the rotor blade and the like. The elongate shaft may for instance be formed by an elongate rod. The elongate shaft may comprise a cylindrical cross-section, an annular cross-section, or the like. The elongate shaft may be manufactured from a metal, or any other suitable material known to the skilled person, such as a composite material, a resinous material, a plastic, et cetera.

In a further preferred example of the actuation device, it further comprises a rotation mechanism, coupled with the second link and configured to be coupled with the high-lift device, wherein the rotation mechanism is configured to rotate the high-lift device upon movement of the second link in the substantially chord-wise direction. The rotation mechanism may be a pivoting lever, pivotally connected with the second link and rigidly connected with the high-lift device. Accordingly, a translational movement of the second link (in the chord-wise direction) may effect a rotational movement of the high-lift device (e.g., a rotation of a trailing-edge flap), thereby altering the camber of the rotor blade.

In a further preferred example of the actuation device, it further comprises an extension mechanism, coupled with the second link and configured to be coupled with the high-lift device, wherein the extension mechanism is configured to extend the high-lift device upon movement of the second link in the substantially chord-wise direction. Accordingly, the extension mechanism may physically extend the high-lift device from a fully stowed position (e.g., a fully retracted position) to a fully deployed position (e.g., a fully extended position) and any position between the fully stowed position and the fully deployed position, thereby altering the chord length, and thus the effective surface area, of the rotor blade.

In a further preferred example of the actuation device, it comprises both an extension mechanism and a rotation mechanism, as described above.

In an alternative example to the above, the translation member may be fixed to the second link instead of the first link. A guiding surface of the translation member may then engage with an engagement element of the first link. The engagement element of the first link may then be provided with bearings, such as roller bearings, engaging with the guiding surface. The above teaching may also be applied to such alternative example, without deviating from the scope of the present disclosure.

In a second aspect of the present disclosure, a rotor blade is provided, comprising a high-lift device and an actuation device according to the first aspect, as described above, wherein the actuation device is coupled with the high-lift device, and particularly, wherein the second link of the actuation device is coupled with the high-lift device. Accordingly, a rotor blade is provided which enables the use (e.g., deployment and stowing) of high- lift devices without adding significant mechanical and control complexity, as the high-lift device is passively actuated. In addition, such rotor blade may reduce the required pitch angle range thereof, i.e., the range of the collective, in comparison to a traditional rotor blade without the actuation device according to the present disclosure. The actuation device is preferably provided in the rotor blade.

Preferably, in the rotor blade of the second aspect of the present disclosure, the first link is movable between a resting position and a maximum outward position, wherein, in the resting position, the high-lift device is in (i.e., actuated to) a fully deployed state (through movement of the second link), and, in the maximum outward position, the high-lift device is in (i.e., actuated to) a fully stowed state (through movement of the second link).

Preferably, in the rotor blade of the second aspect, the high-lift device is at least one of a flap, preferably a trailing-edge flap, and a slat. The flap may be a morphing flap, a split flap, a slotted flap, a Fowler flap, a Junkers flap, a Gouge flap, et cetera. Alternatively or additionally, other actuable aerodynamic surfaces may be provided, which may be actuated by the actuation device of the present disclosure. Such aerodynamic surfaces may include, for instance, speed brakes, spoilers, and other aerodynamic surfaces known to the skilled person. A high-lift device according to the present disclosure may be replaced or supplemented with any other actuable surface without departing from the scope of the present disclosure.

In a third aspect of the present disclosure, a rotor (or propeller) is provided, comprising at least one rotor blade according to the second aspect, as described above. The advantages are described with regard to the rotor blade and actuation device as such.

In a fourth aspect, an aircraft is provided, comprising a rotor (or propeller) according to the third aspect, as described above. Preferably, said aircraft is a rotorcraft or a fixed-wing aircraft. Further preferably, the aircraft is a helicopter. The advantages are described with regard to the rotor blade and actuation device as such. In particular, rotorcraft equipped with the rotor according to the present disclosure benefits from increased lift with reduced rotor speed, which may be beneficial for hovering purposes, e.g., hovering during rescue missions or equipment lifting missions.

The present disclose will further be elucidated with the aid of the appended drawings, wherein:

Figures 1A and IB depict perspective views of an exemplary rotorcraft, specifically a helicopter, and an exemplary fixed-wing aircraft, specifically a propeller aircraft, respectively;

Figure 2 depicts an exemplary rotor;

Figure 3 depicts an exemplary airfoil of a rotor blade equipped with a trailing-edge flap, shown in different states;

Figure 4 depicts a perspective view of an exemplary high-lift device, in particular a trailing edge flap, for a rotor blade, and an exemplary actuation device for actuating the high-lift device; and

Figure 5 depicts a schematic view the exemplary high-lift and actuation devices of Figure 4.

In Figure 1 A, a rotorcraft is shown, in particular a helicopter 1 A. The main lift generating system of the helicopter 1 A is formed by a rotor 10 comprising a number of rotor blades 100. The helicopter 1 A further comprises a tail rotor 20, comprising a number of tail rotor blades 200, which provides a force countering the reactional torque of the main rotor 10 on the fuselage 30 of the helicopter 1 A. The fuselage 30 forms the main body of the helicopter 1 A.

Figure IB depicts a fixed-wing aircraft IB, having a propeller 10B as a main propulsion system. The propeller 10B comprises a number of propeller blades 100B, which rotate to produce an aerodynamic force to propel the aircraft IB. The aircraft IB further comprises a fuselage 30B, a main wing 3 IB for providing lift, and an empennage 32B for providing stability. In the present disclosure, the concepts described in relation to a rotorcraft, such as a helicopter 1A, a rotor 10, and rotor blades 100 may also apply to a fixed-wing aircraft IB, a propeller 10B, and propeller blades 100B, respectively.

In Figure 2, a rotor 10 of a helicopter 1 A is shown. The rotor 10 comprises four rotor blades 100, which are mounted on a rotor hub 11. In turn, the rotor hub 11 is mounted on and driven by a rotor mast 12, which is connected to a driving device (not shown), such as an engine. The rotor blades 100 rotate around a rotation axis 13, which corresponds in this example to the longitudinal axis of the rotor mast 12. In the depicted example, the rotation direction R is shown to be counterclockwise as seen from a top view of the rotor 10. The rotor 10 further comprises a main rotor retaining nut 14, which fixes the rotor 10 to the rotor mast 12.

In order for the helicopter pilot to adjust the pitch angle of the rotor blades 100, the rotor 10 comprises a swash plate assembly 15, comprising an upper swash plate 150, bearings 151, and a lower swash plate 152. The upper swash plate 150 is rotatable with respect to the lower swash plate 152, which is rotationally fixed, by means of the bearings 151, which are generally ball bearings. The upper swash plate 150 rotates together with the rotor 10. The control rods 16 are operable by the helicopter pilot in order to control the helicopter 1A. The control rods 16 control the tilt and height of the swash plate assembly 15. The pitch links 17 are configured to control the pitch angle of the rotor blades 100, and rotate with the rotor blades 100 and the upper swash plate 150.

By raising or lowering the control rods 16, the swash plate assembly 15, and thereby the pitch links 17, are simultaneously, i.e., collectively, raised or lowered, which is controlled by the collective lever operated by the pilot. Hence, the pitch angle of all rotor blades 100 is collectively controlled by the collective lever. Accordingly, the magnitude of the lift vector of the lift generated by the rotor 10 may be controlled with the collective lever, for instance for changing altitude or speed of the helicopter 1A.

The control rods 16 can also be controlled individually, i.e., separately, by means of the cyclic lever controlled by the pilot. By means of the cyclic the pilot is able to tilt the swash plate assembly 15, thereby locally raising or lowering the swash plate assembly 15. The pitch links 17 on the rotating upper swash plate 150 are thus locally raised or lowered during rotation, such that the pitch angle of a rotor blade 100 varies throughout a revolution thereof around the rotation axis 13. Hence, the amount of lift generated by a rotor blade 100 is different at one side of the rotor 10 as compared to another side of the rotor 10. Accordingly, the direction of the lift vector of the lift generated by the rotor 10 may be controlled by the cyclic lever, such that the helicopter 1A may be maneuvered by the pilot, for instance for moving forward, backward, leftward and rightward.

Still referring to Figure 2, the rotor blades 100 comprise a longitudinal axis, also referred to as the span-wise direction S, as the longitudinal axis runs along the span of the rotor blade 100. For each rotor blade 100 a chord-wise direction C is also defined, which is substantially perpendicular to the span- wise direction S. Both the span-wise direction S and the chord-wise direction C lie substantially in the rotation plane of the rotor 10, i.e., the plane wherein the individual span-wise directions S of the rotor blades 100 move upon rotation of the rotor blades 100. The chord-wise direction C may extend in the rotation plane when the pitch angle of the rotor blades 100 is at 0°. Each of the rotor blades 100 in the example of Figure 2 comprises a high-lift device in the form of a trailing-edge flap 200. The flaps 200 may be deployed by rotating them around a hinge axis H of the flap 200, in order to change the camber of the rotor blade 100. Alternatively or additionally, the flaps 200 may be deployed by extending them, i.e., moving them substantially in the chord-wise direction C in order to elongate the airfoil of the rotor blade 100, i.e., in order to increase the effective surface of the rotor blade 100 by increasing the chord length thereof.

In Figure 3 an exemplary airfoil (i.e., cross-sectional shape) of a rotor blade 100 equipped with a trailing-edge flap 200 is shown. In this example, the trailing-edge flap 200 is deployable by means of rotation. The amount of flap rotation is measured from the neutral position N, wherein the chord of the flap is in line with the chord of the airfoil of the rotor blade 100, as indicated in Figure 3. The neutral position N may be parallel to the chord- wise direction C of the rotor blade 100. Depending on circumstances, two or three characterizing rotational positions of the flap 200 may be defined. In the case of a rigid flap 200, two characterizing rotational positions may be identified, being a neutral position N or fully stowed position (rotation of 0° in this case) and a fully deployed position (rotation angle a). In the case of a flexible flap 200 A, such as a morphing flap, a third position may be identified (rotation angle 0), which may be referred to as a relaxed position wherein the flexible flap 200A hangs down due to its flexibility when the rotor 10 is not rotating, i.e., at power-off. The horizontal axis shows the position x along the chord, divided by the chord length c, and the vertical axis shows the position y along the chord, divided by the chord length c. For instance, the neutral position N of the flap 200 may be achieved at 100% RPM (rotations per minute), and the flap 200 may be rotated by rotation angle a at 90% RPM, or the like. Instead of 90%, another relevant or feasible RPM figure may be used, such as 50%, 60%, 70%, 75%, 80%, 85%, or 95%. For a flexible flap 200 A, the rotation of 0 degrees may be achieved at 0% RPM (stand-still), or up to a certain amount of RPM, such as up to 5% or up to 10% or up to 20% RPM, or the like.

Figure 4 shows a high-lift device, in particular a trailing-edge flap 200 and an actuation device 300 for actuation of the flap 200. The actuation device 300 comprises a first link, embodied by a first shaft 301, and a second link, embodied by a second shaft 302. The first shaft 301 extends in the span-wise direction S, and is coupled with a biasing element, embodied by an extension spring 303. The second shaft 302 extends in the chord-wise direction C, and is engaged with a translation member 304, which is fixed to the first shaft 301. The translation member 304 translates a movement of the first shaft 301 in the span- wise direction S to a movement of the second shaft 302 in the chord-wise direction C. The first shaft 301 is supported on span-wise bearing supports 305S, and the second shaft is supported on chord-wise bearing supports 305C. The span-wise bearing supports 305S allow movement of the first shaft 301 in the span-wise direction S, but restrict movement in other directions. The chord-wise bearing support 305C allows for movement of the second shaft 302 in the chord-wise direction C, but restricts movement in other directions. The actuation device 300 also comprises a pre-tensioning element 306 for adjusting the pre-tension on the spring 303.

Upon rotation of the rotor 10, the rotor blades 100 are subjected to a centrifugal force, which is in this example (Figures 4 and 5) directed along the span-wise direction S. The centrifugal force acts upon the first shaft 301 and the translation member 304, as well as the spring 303. Due to its dimensions, the translation member 304 (and thereby the first shaft 301) is movable between a minimum and a maximum outward position, in span-wise direction S, which is delimited in this example by the span- wise bearing supports 305S. The spring 303 applies a resistive, or opposite force to the first shaft 301 in order to (partially) counteract the centrifugal force, depending on the rotational speed of the rotor blades 100 around the rotation axis 13. For instance, when the rotation speed of the rotor blade 100 is decreased, the spring 303 partially of fully overcomes the centrifugal force, such that the first shaft 301 and the translation member 304 move inwardly in the span-wise direction S, i.e., towards the spring 303. For instance, when the rotation speed of the rotor blade 100 is increased, the centrifugal force partially or fully overcomes the opposite force generated by the spring 303, such that the first shaft 301 and the translation member 304 move outwardly in the span-wise direction S, i.e., away from the spring 303. In the example of Figure 4, the second shaft 302 is moved outwardly in the chord-wise direction C, i.e., away from the first shaft 301. The second shaft 302 is connected with the flap 200 through a rotation mechanism 201, which translates a movement of the second shaft 302 in the chord- wise direction C to a rotation of the flap 200 around its hinge axis H. The actuation device 300 further comprises a housing 307, fixed to the rotor 10, and specifically the rotor blade 100. The actuation device 300, and in particular the translation member 304 will be described in further detail with reference to Figure 5 below.

In Figure 5 a schematic view of the actuation device 300 and the flap 200 of Figure 4 is shown. The spring 303 is connected with the pre-tensioning element 306 and the first shaft 301. The pretensioning element is fixed to the housing 307 by means of fastening elements, such as nuts and bolts. The first shaft 301 is movable in the span-wise direction S, and is supported and guided by the span-wise bearing supports 305S. The translation element 304 is fixedly connected with the first shaft 301, and is movable between the span-wise bearing supports 305S simultaneously with the first shaft 301. Due to the dimensions of the translation element 304 the movement of the translation element 304 and the first shaft 301 is restricted by the span-wise bearing supports 305S. The second shaft 302 is guided and supported by the chord-wise bearing support 305C, and is therefore movable in the chord-wise direction C. The second shaft 302 is coupled, with its actuation end 3020, to the aforementioned rotation mechanism 201, for rotating the flap 200 about its hinge axis H. Furthermore, the second shaft 302 is coupled, with its engagement end 3021, with the translation element 304.

In particular, the engagement end 3021 of the second shaft 302 is engaged in a sloped guiding groove 3040 of the translation member 304. Preferably, the engagement end 3021 comprises roller bearings or the like, in order to be guided through the groove 3040 with low friction. The groove 3040 defines a sloped path, i.e., an inclined path, with respect to the first shaft 301, and thus the span-wise direction S. Due to the first shaft 301 and the second shaft 302 being restricted in movement in the span-wise S and chord-wise C directions, respectively, the guiding groove 3040 is able to move the second shaft 302 in the chord-wise direction C, upon movement of the first shaft 301 in the span-wise direction S. In the shown example, the guiding groove 3040 is configured such that the second shaft 302 is moved outwardly in the chord-wise direction C upon movement of the first shaft 301 in the span-wise direction S. In other words, the guiding groove 3040 increases the distance between the second shaft 302 and the first shaft 301 with increasing centrifugal force. Advantageously, the translation member 304 provides additional mass to the first shaft 301 in order to increase the effect of the centrifugal force upon the first shaft 301. The guiding groove 3040 may define a guiding path different than the exemplary one in Figure 5, depending on the needs. For instance, the guiding path provided by the guiding groove 3040 may be non-linear, in order to establish non-linear deployment (and stowing) of the high-lift device connected to the actuation device 300.

As described above, the present disclosure provides an actuation device 300 capable of passively controlling a high-lift device, such as a flap 200, based on centrifugal force experienced by the rotor blade 100 upon rotation of the rotor 10. For instance, a flap 200 may be deployed (e.g., deflected, rotated) when the rotation speed of the rotor 10 of an aircraft is reduced, so as to provide a greater lift force at reduced RPM (rotations per minute). In turn, the burden on the collective (the required pitch angle control range) is thereby decreased in that situation. The actuation device 300 may be tuned (e.g., by changing characteristics of the spring 303, by tuning the pre-tension on the spring 303 by means of the pre-tensioning element 306, et cetera) such that the collective requires little or no actuation upon reduction of the RPM of the rotor 10 from maximum RPM to a lower RPM (e.g., 70%, 80%, or 90% of the maximum RPM, or any other relevant and/or feasible reduced RPM figure). In the above examples, the high-lift device is a rotatable flap 200. However, as is to be understood from the present disclosure, the same teaching applies to extension of a flap 200, or simultaneous extension and rotation of a flap 200. In addition, the above examples relate to a high-lift device, and specifically a trailing-edge flap 200. However, as is to be understood from the present disclosure, the same teaching applies to different actuable surfaces, such as slats, air brakes, spoilers, and the like. Further, as is to be understood from the present disclosure, depending on the rotation or extension mechanism of the high-lift device, the direction of movement of the second link 302 may be reversed, in comparison to the above examples. For instance, a rotation of a flap 200 may be effected by either pushing or pulling the second link 302 by means of the translation member 304 fixed to the first link 301. In similar fashion, the order of “deploying” and “stowing” of the high-lift device may be reversed as well. For instance, at maximum centrifugal force, the high-lift device may either be stowed or deployed, depending on design constraints.

The figures and the accompanying description provided herewith are merely for illustrative purposes, i.e., exemplary purposes, in order to aid the reader in understanding the present disclosure. These above illustrated examples are not to be interpreted as limiting the scope of the present disclosure in any way or form.

Claims

CLAIMS Actuation device (300) for actuating a high- lift device (200) of a rotor blade (100), comprising: a first link (301), movable in a substantially span-wise direction (S) of the rotor blade (100), and outwardly in the substantially span-wise direction (S) by a centrifugal force generated by rotation of the rotor blade (100); a biasing member (303), connected with the first link (301) and configured to exert an opposite force thereon, opposite the centrifugal force, so as to bias the first link (301) inwardly in the substantially span-wise direction (S); a second link (302), movable in a substantially chord-wise direction (C) of the rotor blade (100) and configured to be coupled with the high-lift device (200); and a translation member (304), coupled with the first link (301) and the second link (302), wherein the translation member (304) is configured to be movable by movement of the first link (301) in the substantially span-wise direction (S), thereby effecting movement of the second link (302) in the substantially chord-wise direction (C), so as to actuate the high-lift device (200), wherein the second link (302) comprises an engagement end (3021), engaged with the translation member (304), and an actuation end (3020), configured to be coupled with the high-lift device (200), and the translation member (304) comprises a guiding element (3040), engaged with the engagement end (3021) of the second link (302), wherein the guiding element (3040) is configured to guide the second link (302) in the substantially chord-wise direction (C) upon movement of the first link (301) along the substantially span-wise direction (S). Actuation device (300) according to claim 1, wherein the substantially span-wise direction (S) is substantially orthogonal to the substantially chord-wise direction (C). Actuation device (300) according to claim 1 or 2, wherein the translation member (304) is fixed to the first link (301), such that the translation member (304) is movable in the substantially span-wise direction (S) simultaneously with the first link (301). Actuation device (300) according to any of the preceding claims, wherein the guiding element (3040) comprises a guiding surface, configured to guide the engagement end (3021) of the second link (302), wherein the guiding surface defines a guiding path which lies substantially in a movement plane, defined by the substantially chord- wise (C) and substantially span-wise directions (S). Actuation device (300) according to claim 4, wherein the guiding path is a sloped guiding path, which is sloped with respect to the substantially span-wise direction (S). Actuation device (300) according to claim 4 or 5, wherein the guiding element (304) comprises a guiding groove (3040), which includes the guiding surface, wherein the engagement end (3021) of the second link (302) is coupled with the guiding groove (3040). Actuation device (300) according to claim 6, wherein the guiding groove (3040) comprises a retention element, configured to retain the engagement end (3021) of the second link (302) in the guiding groove (3040). Actuation device (300) according to any one of claims 4 - 7, wherein the engagement end (3021) of the second link (302) is engaged with the guiding surface by means of a bearing, preferably a roller bearing Actuation device (300) according to any of the preceding claims, wherein the biasing member is a spring (303). Actuation device (300) according to any of the preceding claims, wherein the first link (301) and/or the second link (302) is an elongate shaft. Actuation device (300) according to claim 10, wherein the elongate shaft is constrained by supports (305S, 305C), allowing movement of the elongate shaft in longitudinal direction thereof, preferably wherein the supports are bearing supports (305S, 305C). Actuation device (300) according to any of the preceding claims, further comprising a rotation mechanism (201), coupled with the second link (302) and configured to be coupled with the high-lift device (200), wherein the rotation mechanism (201) is configured to rotate the high-lift device (200) upon movement of the second link (302) in the substantially chord-wise direction (C). 17 Actuation device (300) according to any of the preceding claims, further comprising an extension mechanism, coupled with the second link (302) and configured to be coupled with the high-lift device (200), wherein the extension mechanism is configured to extend the high-lift device (200) upon movement of the second link (302) in the substantially chord-wise direction (C). Rotor blade (100), comprising: a high-lift device (200); and an actuation device (300) according to any of the preceding claims, preferably provided in the rotor blade (100), coupled with the high-lift device (200). Rotor blade (100) according to claim 14, wherein the first link (301) is movable between a resting position and a maximized position, wherein, in the resting position, the high-lift device (200) is in a fully deployed state, and, in the maximized position, the high- lift device (200) is in a fully stowed state. Rotor blade (100) according to claim 14 or 15, wherein the high-lift device (200) is at least one of a flap, preferably a trailing-edge flap (200), and a slat. Rotor (10) for an aircraft (1A, IB), comprising at least one rotor blade (100) according to any one of claims 14 - 16. Aircraft (1A, IB) comprising a rotor (10) according to claim 17, preferably wherein said aircraft (1A, IB) is a rotorcraft (1A), and more preferably a helicopter (1A).