Patent Description:
Lift spoiling and drag devices are typically used to disrupt airflow around aerodynamic bodies. The devices are designed to be actuated to deploy into the airflow over the aerodynamic surface to disrupt the oncoming airflow over that surface. The devices may retract either to form part of the aerodynamic profile of the structure or inside that structure behind the aerodynamic surface.

Lift spoiling and drag devices may be generally termed as flow control devices and have a control surface, i.e. the aerodynamic surface of the flow control device that is primarily acting to alter the airflow. There are a wide variety of such known flow control devices, including spoilers, lift dumpers, air brakes (also known as speed brakes or dive brakes). Generally, lift spoiling devices reduce the lift-to-drag ratio and require a higher angle of attack to maintain lift, whereas drag devices are designed to increase drag with little change to lift. Sometimes the function of these lift spoiling or drag devices may be combined with the function of other flow control devices, e.g. on an aircraft a spoileron acts as both a spoiler and an aileron for roll control.

These flow control devices are actuated and deployed by a variety of means, including linkages, linear and rotary mechanisms, and the like. Depending on the kinematic of the deployment some of these mechanisms may be complex and may be cumbersome and occupy a large volume of space within the structure. The aperture or opening through which the control surface deploys, or the void created in the aerodynamic surface of the structure when the control surface deploys, may be large. In some circumstances it is desirable to reduce the size of this aperture and to make the control surface deployment mechanism small in order to enhance the aerodynamic performance of the aerodynamic body when the control surface is retracted, deployed or both. <CIT> describes a control device for airplanes.

According to an aspect of the invention, there is provided an aerodynamic control surface assembly comprising: a structure with an aerodynamic surface; an aerodynamic control surface having a height dimension and configured to move between an extended and a retracted position, wherein the aerodynamic control surface has a curved profile in the height dimension; an actuation mechanism coupled to the aerodynamic control surface and configured to move the aerodynamic control surface between the extended and retracted positions,wherein the aerodynamic control surface is arranged to deploy through an aperture in the aerodynamic surface and into an oncoming airflow over the aerodynamic surface when in the extended position and is arranged to retract out of the airflow when in the retracted position,wherein the actuation mechanism is configured such that the control surface follows a curved kinematic path as the control surface moves between the extended and retracted positions, and wherein the actuation mechanism remains fully behind the aerodynamic surface throughout the movement of the aerodynamic control surface between the extended and retracted positions, and wherein the curved kinematic path has variable radii along the path length.

An aerodynamic control surface is a device which controls the direction of air flow over the structure with an aerodynamic surface.

The actuation mechanism does not extend into an oncoming airflow over the aerodynamic surface. The actuation mechanism does not disrupt the airflow over the aerodynamic surface of the structure.

The curved kinematic path can be optimised to maximise the disruption to the oncoming airflow over the aerodynamic surface of the structure.

The actuation mechanism may comprise a four-bar linkage mechanism.

The motion of the four-bar link mechanism may cause motion of the aerodynamic control surface along the curved kinematic path. The deployment and retraction of the aerodynamic control surface may be effected by reciprocating motion of the four-bar link mechanism. The four-bar link mechanism may occupy a relatively small space within the structure and the lengths of each bar of the four-bar link mechanism may be tuned to achieve a desired curved kinematic path.

The four-bar linkage mechanism may comprises: a grounded link fixed with respect to the structure; a first crank pivotably coupled at one end to the grounded link and pivotably coupled at a second end to a coupling link; a second crank pivotably coupled at one end to the grounded link and pivotably coupled at a second end to the coupling link; wherein the aerodynamic control surface is rigidly fixed with respect to either the coupling link or one of the first and second cranks.

The pivoting movement of the first crank and the second crank provides a reciprocating motion of the coupling link. Rigidly fixed means that the aerodynamic control surface does not rotate with respect to the coupling link.

The coupling link may have an extension which extends away from the pivotal connections of the coupling link towards the grounded link.

The extension of the coupling link may be rigidly fixed with respect to the aerodynamic control surface. The extension may have a proximal end nearest the pivotal connections of the coupling link and a distal end nearest the grounded link.

The aerodynamic control surface may be rigidly fixedly connected to the extension at the distal end of the extension.

The aerodynamic control surface may have a flow surface facing the oncoming airflow which is convex or concave.

The aerodynamic control surface may be formed as a blade.

A blade may be a panel, in particular a thin sheet or plate.

The blade may have a substantially constant thickness or a taper of reducing thickness towards a cantilevered free end of the blade, i.e. further from the attachment to the actuation mechanism.

The profile of the blade may have a curvature which substantially matches the path of variable curvature of the actuation mechanism such that the aperture in the aerodynamic surface has a width substantially the same as the maximum thickness of the blade.

As the blade moves along the kinematic curve path, due to the curved profile of the blade, the aperture only needs to be as wide as the local thickness of the blade along the curved kinematic path followed by the blade during deployment and retraction. (with a toleranced clearance) to pass through. This may be equal to or greater than the maximum blade thickness. This may reduce the size of aperture needed in the structure, which may beneficially avoid disruption to airflow over the aerodynamic surface when the control surface is retracted (i.e. the aerodynamic 'clean' state of the aerodynamic surface).

The aerodynamic control surface may be non-linear in a direction transverse to the oncoming airflow direction.

The non-linear profile of the control surface in the direction transverse to the oncoming airflow may help improve the stiffness of the control surface for a given length, height and weight of the control surface.

The shape of the control surface in the transverse direction may be a corrugation.

The aerodynamic control surface may be rigid.

The aperture in the structure may be tapered towards the aerodynamic surface.

The tapered profile of the aperture through the structure (e.g. through a cover panel having the aerodynamic surface) may allow sufficient clearance with the control surface during deployment along the curved kinematic path, while ensuring the aperture dimension at the aerodynamic surface of the structure is minimised. The local angle of the control surface with the aperture may change during the movement along the kinematic path and so the profile of the aperture through the structure may be tapered to avoid any clash. The aperture can be sized to match the kinematic path of the aerodynamic control surface and reduce any unwanted drag effects caused by larger apertures.

The aerodynamic control surface may further comprise a seal for sealing the aperture.

The seal may sit flush in the aperture to seal the aperture when the aerodynamic control surface is in the retracted position. This may provide a smoother airflow over the aerodynamic surface of the structure.

The actuation mechanism may further comprise an actuator, preferably a rotary or linear actuator.

The flow surface of the aerodynamic control surface may not form part of the aerodynamic surface of the structure.

When the aerodynamic control surface is in the retracted position, airflow over aerodynamic profile of the structure with the aerodynamic surface may have fewer disruptions and surface discontinuities as compared to the airflow over the structure when flow control devices arranged to retract and form part of, or sit continuous with, the aerodynamic surface of the structure.

The aerodynamic control surface assembly may be used in or on a vehicle, such as a car, truck, bus, ship, aircraft or helicopter, or structures which control aerodynamic flow, such as wind turbines or water turbines.

An aircraft assembly may comprise the aerodynamic control surface assembly.

In an aircraft, the aerodynamic control surface may be a spoiler, spoileron, lift dumper, air brake, speed brake or dive brake.

The aerodynamic control surface assembly may be on the fuselage, empennage, tailplanes, or wings.

The structure may be an aircraft wing and the aerodynamic surface may be a surface of the wing.

The aerodynamic control surface may be on an upper and/or lower aerodynamic surface of the wing.

In a further aspect of the invention there is a method of controlling airflow over a structure with an aerodynamic surface using an aerodynamic control surface, wherein the aerodynamic control surface has a height dimension and has a curved profile in the height dimension, the method comprising:actuating an actuation mechanism coupled to the aerodynamic control surface to: i) move the aerodynamic control surface through an aperture in the aerodynamic surface into an oncoming airflow over the aerodynamic surface to place the aerodynamic surface in an extended position, and ii) move the aerodynamic control surface through the aperture in the aerodynamic surface into a space behind the aerodynamic surface and out of the airflow to place the aerodynamic surface in a retracted position, wherein the actuation mechanism is configured such that the control surface follows a curved kinematic path as the control surface moves between the extended and retracted positions,wherein the actuation mechanism remains fully behind the aerodynamic surface throughout the movement of the aerodynamic control surface between the extended and retracted positions, and wherein the curved kinematic path has variable radii along the path length.

<FIG> shows an aircraft <NUM> with port and starboard fixed wings, <NUM>, <NUM>, a fuselage <NUM> and a nose end <NUM> and a tail end <NUM> including horizontal and vertical stabilising surfaces 6a, 6b. Each wing has a leading edge 2a, 3a and trailing edge, 2b, 3b. The aircraft <NUM> is a typical jet passenger transonic transport aircraft but the invention is applicable to a wide variety of fixed wing aircraft types, including commercial, military, passenger, cargo, jet propeller, general aviation etc. with any number of wings attached to the wings or fuselage. The invention may also be applied to rotary wing aircraft and other aerodynamic bodies such as wind turbine blades, land vehicles, etc..

The axes shown in <FIG> represents the usual reference orthogonal axes of the aircraft <NUM>. The X-axis defines the longitudinal fore-aft direction of the aircraft; the Y-axis defines the spanwise direction and the Z-axis defines the vertical up-down direction of the aircraft.

Each wing <NUM>,<NUM> of the aircraft has a cantilevered structure with a length extending in a spanwise direction from a root to a tip, the root being joined to the aircraft fuselage <NUM>. The wing portion near the root is in the inboard region. The wing portion near the tip is called the outboard region. The wing has an upper aerodynamic surface <NUM> and the lower aerodynamic surface <NUM>. At the tip end of each wing <NUM>, <NUM> is a wing tip device <NUM> outboard of a main portion of the wing.

The wing has an outer aerodynamic surface. The wings <NUM>,<NUM> are aft swept and have a number of aerodynamic flight control surfaces. The flight control surfaces can be adjusted during flight to adjust the aircraft flight attitude or wing performance. There are a number of flight control surfaces, such as ailerons, elevator, rudders, spoilers, flaps, slats and air brakes. These are typically located on the wing <NUM>,<NUM> or on the horizontal stabiliser 6a or vertical stabiliser 6b of the aircraft <NUM>.

The main lift dumping spoilers are typically found on the trailing edge 2b, 3b of the aircraft just forward of the flaps. The aerodynamic control surface <NUM> shown in <FIG> is configured as a lift dump spoiler. The aerodynamic control surface <NUM> can be moved between a retracted position <NUM> and a deployed position <NUM>. While the aerodynamic control surface <NUM> is shown in <FIG> to be located outboard of the aircraft wing, near the wing tip device <NUM>, the spoiler <NUM> may be at any suitable position along the span of the wing <NUM>.

<FIG> shows the aerodynamic control surface <NUM> arranged on the wing <NUM>, shown schematically in <FIG>. As shown in <FIG>, the aerodynamic control surface <NUM> extends away from the upper surface <NUM> to disrupt the oncoming airflow A over the wing <NUM> in the deployed position <NUM>.

As the wings <NUM>, <NUM> are similar in construction, the wing <NUM> may have a similar aerodynamic control surface <NUM> for symmetry with the wing <NUM>. It will be understood that each aerodynamic control surface <NUM> may be deployed simultaneously or independently.

The aerodynamic control surface <NUM> has a proximal end 20a and a distal end 20b. The distal end 20b of the aerodynamic control surface <NUM> extends away from the proximal end 20a towards an aperture <NUM> in the upper surface <NUM> of the wing <NUM>. The aerodynamic control surface <NUM> has a length L and a thickness T. The aerodynamic control surface has a flow surface (facing the oncoming airflow A), 20c and an opposing surface (reverse) 20d. The flow surface 20c may be concave to disrupt the oncoming airflow A, as shown in <FIG>. Alternatively, the flow surface 20c may be convex (as shown in <FIG>). The method of controlling the airflow over the wing <NUM> using the aerodynamic control surface <NUM> with one of the exemplary actuation mechanisms <NUM>, <NUM> and <NUM>, which will be described in greater detail below.

<FIG> shows a schematic of the cross-section (through A-A of <FIG>) of an aircraft wing <NUM> with an aerodynamic control surface <NUM> in an example not being part of the claimed subject-matter. This example relates to an aerodynamic control surface <NUM> actuated by actuator mechanism <NUM>. <FIG> shows the aerodynamic control surface <NUM> in a retracted state <NUM>, and <FIG> show the aerodynamic control surface <NUM> deploying through intermediate position <NUM> to a fully extended position <NUM>.

The aerodynamic control surface <NUM> is in a fully retracted position <NUM> in an initial or first position 52a of the actuator mechanism as shown in <FIG>. In the first position 52a, the aerodynamic control surface <NUM> does not extend past the upper aerodynamic surface <NUM> of the wing <NUM>. In a third position 52c, corresponding to the fully deployed state <NUM>, the aerodynamic control surface <NUM> extends through the aperture <NUM> in the wing aerodynamic surface <NUM> into the oncoming airflow moving in direction A. The actuator mechanism <NUM> is a linear linkage with a length, AL. The actuation mechanism <NUM> is pivotally connected to the structure of the aircraft wing at a first end <NUM> of the linear linkage for simple rotation about point <NUM>.

The proximal end 20a of the aerodynamic control surface is rigidly fixed to a second end <NUM> of the linear linkage of the actuation mechanism <NUM> opposite the first end <NUM>. That is to say, the proximal end 20a of the aerodynamic control surface <NUM> does not rotate with respect to the linear linkage but moves with the rotation of the linear linkage about the pivot at <NUM>. The proximal end 20a may be attached by any suitable mechanical means, for example, bolting or welding. The actuation mechanism <NUM> is operated by an actuator, either directly or indirectly, such as a rotary or linear actuator (not shown) to move the actuation mechanism <NUM> from the first position 52a to the third position 52c. The actuation mechanism <NUM> may be deployed from the first position 52a through to 52c or may be deployed from only the first position 52a to the second position 52b. The range of movement of the control surface <NUM> is shown by the dotted line <NUM> in <FIG>. The actuation of the actuator mechanism <NUM> may be controlled by a control system of the aircraft <NUM>.

<FIG> shows the actuation mechanism <NUM> in a second position 52b and with the first position 52a in dotted lines. The second position 52b of the actuation mechanism moves the aerodynamic control surface <NUM> through the aperture <NUM> in the wing <NUM>. The aerodynamic control surface <NUM> moves along a curved kinematic path <NUM> as the actuation mechanism <NUM> moves from the first position 52a towards the final position 52c. The curved kinematic path <NUM> indicates the path that the aerodynamic control surface <NUM> moves from the retracted state <NUM> to the deployed state <NUM>.

<FIG> shows the deployed state <NUM> of the aerodynamic control surface <NUM> and the third position 52c of the actuator mechanism <NUM> and with the first position in dotted lines. In the third position 52c the actuation mechanism <NUM> has rotated from the first position 52a until the linear linkage is approximately parallel with the aerodynamic surface <NUM> and the second end <NUM> of the linear linkage is directly below the aperture <NUM>. The aerodynamic control surface <NUM> extends through the aperture <NUM> into the oncoming airflow A. As the actuation mechanism <NUM> moves from the first position 51a to the third position 52c, the actuation mechanism <NUM> does not extend through the aperture <NUM>. That is to say, the actuation mechanism <NUM> remains at all times behind the aerodynamic surface <NUM> of the wing <NUM>. As the actuation mechanism <NUM> does not extend through the aperture <NUM>, this naturally limits the extent of deployment of the aerodynamic control surface <NUM> but means that the size of the aperture <NUM> is only large enough for the curved control surface <NUM> to pass through and does not need to accommodate any part of the action mechanism <NUM>, thus minimising the size of the aperture <NUM>.

The curved kinematic path <NUM> of the spoiler <NUM> is defined by the length AL of the actuator mechanism <NUM> as it rotates around the pivot point <NUM>. The curved kinematic is therefore a simple radius about point <NUM>. The curved kinematic path <NUM> of the spoiler <NUM> can be tailored by altering the length of the actuator mechanism <NUM>. The proximity of the aerodynamic control surface <NUM> or the actuation mechanism <NUM> to the aerodynamic surface <NUM> can also be altered to tailor the curved kinematic path <NUM>. The curvature of the concave control surface substantially matches the curved kinematic path <NUM> so that the radius of the curved flow surface 20c is substantially identical to the radius of the kinematic path <NUM>. The control surface <NUM> may have a substantially constant thickness T along its height H so that the size of the aperture <NUM> may be minimised. Alternatively, the control surface <NUM> may have a taper of reducing thickness towards the cantilevered free end of the control surface, furthest from the actuation mechanism. Additionally or alternatively, the control surface <NUM> may have one or more stiffeners spaced width-wise along the length of the control surface on the reverse surface opposite the flow surface.

In the extended position <NUM>, the flow surface 20c of the aerodynamic control surface <NUM> faces towards the oncoming airflow A, i.e. is concave. This alters the flow of air over the wing by spoiling the lift and decreases the lift of the local aerofoil section and hence reduces the lift and/or increases the drag generated by the wing <NUM>. The spoiler <NUM> is retracted back into the wing <NUM> in the opposite manner i.e. the actuating mechanism <NUM> moves between the spoiler <NUM> from a third position 52c back to the first position 52a.

In the example described above with respect to <FIG>, the actuation mechanism <NUM> is configured as a linear linkage or arm that rotates around a single point <NUM>. <FIG> and <FIG> shows the schematic views cross-section (through A-A of <FIG>) of an aircraft wing <NUM> with a spoiler <NUM> in a second and third example. These examples relate to an aerodynamic control surface arranged with a four-bar link mechanism actuation system. Similar to <FIG>, <FIG> and <FIG> show the aerodynamic control surface <NUM> deploying from a fully retracted position <NUM> and deploying through intermediate positions <NUM> to a fully extended position <NUM> and the second exemplary actuation mechanism <NUM> and the third exemplary actuation mechanism <NUM> moving through a first position 152a, 252a to a final position 152c, 252c, respectively.

<FIG> shows the spoiler <NUM> in a fully retracted position <NUM> in the initial position 152a of the horizontal four-bar link mechanism <NUM>. Similar to the example described in <FIG>, the aerodynamic control surface <NUM> moves from below the aerodynamic upper surface <NUM> of the wing <NUM> through the aperture <NUM> into the oncoming airflow A. The actuation mechanism <NUM> comprises a four-bar link mechanism with a grounded link <NUM> which is shown schematically in <FIG> but has been omitted from <FIG> for clarity. The grounded link <NUM> is secured to or forms part of the wing <NUM>, or another structural element within the wing. The four-bar link mechanism <NUM> has a first crank <NUM> with a first end 156a and a second end 156b. The four-bar link mechanism <NUM> also has a second crank <NUM> with a first end 158a and a second end 158b. The first end of the first crank 156a is pivotally connected to the grounded link <NUM> at the connection point 156c. Similarly, the first end of the second crank 158a is pivotally connected to the grounded link <NUM> at the connection point 158c.

The first crank <NUM> pivots around the grounded link <NUM> at the connection point 156c and the second crank <NUM> pivots around the grounded link <NUM> at the connection point 158c as the four-bar link mechanism moves from the first position 152a to the deployed position 152c.

The second end 156b of the first crank <NUM> is pivotably coupled to a coupling link <NUM>. Similarly, the second end 158b of the second crank is pivotably coupled to the coupling link <NUM> at a point spaced along the coupling link away from the second end 156b of the first crank. The coupling link <NUM> extends between the second ends 156b, 158b of the first and second crank. The aerodynamic control surface <NUM> is rigidly fixed to the coupling link <NUM> at the proximal end of the spoiler 20a, i.e. the control surface <NUM> does not rotate with respect to the coupling link <NUM>.

As shown in <FIG>, the aerodynamic control surface <NUM> is in a retracted state <NUM> and the second exemplary actuation mechanism <NUM> is in the first position 152a. In the first position 152a, the spoiler <NUM> does not extend beyond the upper surface <NUM> of the wing <NUM>. As the four-bar link mechanism <NUM> moves to the deployed position 152c (where the spoiler <NUM> is in a fully deployed position <NUM>), the first crank <NUM> and the second crank <NUM> pivot around the grounded link <NUM> to extend the aerodynamic control surface <NUM> through the aperture <NUM>. The movement of the first crank <NUM> and the second crank <NUM> moves the coupling link <NUM> and consequently the spoiler <NUM> along a complex curved kinematic path <NUM> (shown in dotted lines in <FIG>). The curved kinematic path <NUM> has a variable radii along the path <NUM>.

As shown in <FIG> and <FIG>, the first crank <NUM> and the second crank <NUM> are configured to rotate around the grounded link <NUM> in the same direction until the aerodynamic control surface <NUM> extends through the aperture <NUM> and the flow surface 20c is facing into the oncoming airflow direction A.

Alternatively, the aerodynamic control surface <NUM> may be rigidly secured to the second end 156b of the first crank <NUM>, or the second end 158b of the second crank <NUM>.

<FIG> shows the deployed state <NUM> of the spoiler <NUM> and the third position 152c of the four-bar link mechanism <NUM>. In the third position 152c, the first crank <NUM> and the second crank <NUM> rotate around the ground link <NUM> until the coupling link <NUM> is adjacent the reverse face of the wing cover having the aerodynamic surface <NUM>. The aerodynamic control surface <NUM> extends through the aperture <NUM> into the oncoming airflow A. As the four-bar link mechanism <NUM> moves from a first position 152a to the third position 152c, the four-bar link mechanism <NUM> does not extend through the aperture <NUM>. That is to say, the four-bar link mechanism <NUM> remains below the upper surface <NUM> of the wing <NUM>. As the four-bar link mechanism <NUM> does not extend through the aperture <NUM>, this naturally limits the extent of deployment of the aerodynamic control surface <NUM> but means that the size of the aperture <NUM> is only large enough for the curved control surface <NUM> to pass through and does not need to accommodate any part of the action mechanism <NUM>, thus minimising the size of the aperture <NUM>.

Since the actuation mechanism <NUM> is a four-bar linkage and not a simple linear linkage (like in the actuation mechanism <NUM>), the kinematic path is not a simple radiused curve but has complex curvature. This means that the control surface <NUM> can have a profiled curvature in the height direction H which is also not a simple radius but can have a curvature of variable radii along its height dimension. The curvature of the profile of the control surface <NUM> can be tailored to minimise the size of the aperture <NUM> for a given kinematic of the actuation mechanism <NUM>. The kinematic of the actuation mechanism <NUM> can be tailored by adjusting the lengths of the linkages of the four bar linkage mechanism. The proximity of the aerodynamic control surface <NUM> or the actuation mechanism <NUM> to the aerodynamic upper surface <NUM> can also be altered to tailor the complex curved kinematic path <NUM>. This provides a great deal of flexibility to design the shape of the kinematic path and the shape of the flow surface of the control surface to meet various design criteria. These criteria may include a space envelope within the wing <NUM> for accommodating the actuation mechanism, a particular profile of the curved control surface, a desired drag or lift spoiling characteristic of the control surface, etc..

<FIG> show another example of a four-bar link mechanism <NUM> moving from a first position 252a to a final position 252c. <FIG> shows the spoiler <NUM> in a fully retracted position <NUM> in the initial position 252a of the third exemplary actuation mechanism <NUM>. Similar to the example in <FIG>, the third exemplary actuation mechanism <NUM> comprises a four-bar link mechanism <NUM> with a first crank <NUM> with a first end 156a and a second end 156b. The four-bar link mechanism <NUM> also has a second crank <NUM> with a first end 158a and a second end 158b. The second end of the first crank 156b is pivotally connected to a grounded link <NUM> at the connection point 156b. Similarly, the second end of the second crank 158b is pivotally connected to the grounded link <NUM> at the connection point 158b. The grounded link has been omitted from <FIG>- and 6B for clarity but is shown in <FIG>.

The first end 156a of the first crank <NUM> is pivotably coupled to one end 259a of the coupling link <NUM>. Similarly, the first end 158a of the second crank <NUM> is pivotably coupled to another end 259b of the coupling link <NUM>. The coupling link <NUM> has an extension 259d which extends away from the pivotal connections (between i. the first end 156a of the first crank <NUM> and the end 259a of the coupling link and ii. the first end 158a of the second crank <NUM> and the end 259b of the coupling link <NUM>) towards the grounded link (not shown in <FIG>). The extension 259d extends to an apex 259c. In this example, the coupling link <NUM> and the extension are unitary and form a generally triangular plate. The aerodynamic control surface <NUM> is rigidly fixed to the coupling link <NUM> at the apex 259c by the proximal end of the aerodynamic control surface 20a. It will be understood that the coupling link and the extension may take a variety of shapes and need not be triangular, for example, it may be T-shaped with the coupling link forming the top of horizontal top of the T shape and the extension forming the vertical leg of the T shape. The four-bar mechanism <NUM> with the coupling link <NUM> having the extension 259d may be a commonly known Roberts mechanism.

The first crank <NUM> pivots around the grounded link <NUM> at the connection point 156b and the second crank <NUM> pivots around the grounded link <NUM> at the connection point 158b as the four-bar link mechanism moves from the first position 252a to the deployed position 252c.

As shown in <FIG>, the aerodynamic control surface <NUM> is in a retracted state <NUM> and the four-bar link mechanism <NUM> is in the first position 252a. In the first position 252a, the aerodynamic control surface <NUM> does not extend beyond the upper surface <NUM> of the wing <NUM>. As the four-bar link mechanism <NUM> moves to the deployed position 252c (where the aerodynamic control surface <NUM> is in a fully deployed position <NUM>), the first crank <NUM> and the second crank <NUM> pivot around the grounded link <NUM> to extend the aerodynamic control surface <NUM> through the aperture <NUM>. The movement of the first crank <NUM> and the second crank <NUM> moves the coupling link <NUM> and consequently the aerodynamic control surface <NUM> along a curved kinematic path <NUM> (shown in dotted lines). The curved kinematic path <NUM> has variable radii along the path <NUM>.

<FIG> shows the deployed state <NUM> of the aerodynamic control surface <NUM> and the third position 252c of the four-bar link mechanism <NUM>. In the third position 252c, the first crank <NUM> and the second crank <NUM> rotate around the ground link <NUM> until the apex of the coupling link <NUM> is directly below the aperture <NUM>. The aerodynamic control surface <NUM> extends through the aperture <NUM> into the oncoming airflow A. As the four-bar link mechanism <NUM> moves from a first position 252a to the third position 252c, the four-bar link mechanism <NUM> does not extend through the aperture <NUM>.

The variable radii curved kinematic path <NUM> of the aerodynamic control surface <NUM> is defined by the length and arrangement of the first crank <NUM>, the second crank <NUM> and the shape of the coupling link <NUM>. As such, the curved variable radii kinematic path <NUM> of the aerodynamic control surface <NUM> can be tailored, similar to the tailoring of the actuation mechanism <NUM>. The proximity of the aerodynamic control surface <NUM> or the actuation mechanism <NUM> to the aerodynamic upper surface <NUM> can also be altered to tailor the variable radii curved kinematic path <NUM>. The curved profile of the control surface <NUM> in the height dimension can also be tailored depending on the kinematic path of the actuation mechanism <NUM>, e.g. to minimise the size of the aperture <NUM>.

In the example described in <FIG>, the first crank <NUM> and second crank <NUM> are arranged to rotate around the grounded link <NUM> in the same direction at an approximately equivalent angular rate. That is the say, the second end of the first and second cranks 156b, 158b rotate in the same direction with respect to the coupling link <NUM> as the first crank <NUM> and the second crank <NUM> rotate around the grounded link <NUM>. The first crank <NUM> and second crank <NUM> are arranged generally parallel to each other in this example in all positions of the actuation mechanism.

In the four-bar linkage of the actuation mechanism <NUM> shown in the example in <FIG>, whilst the first crank <NUM> and second crank <NUM> are arranged to rotate around the grounded link <NUM> in the same direction, the first and second cranks rotate at different angular rates during the deployment. In this example, the first crank <NUM> and the second crank <NUM> are not arranged parallel to each other. Instead, the distance between second end of the first crank 156b and the second end of the second crank 158b is greater than the distance between the first end of the first crank 156a and the first end of the second crank 158a. The end of the coupling link <NUM> that is pivotally connected at 259a and 259b to the first and second cranks <NUM>, <NUM> generates a mechanical advantage at the apex 259c so that relatively small angular rotations of the first and second cranks <NUM>, <NUM> causes a larger movement of the apex 259c of the coupling link <NUM>. Since the control surface <NUM> is fixed to the apex 259c of the coupling link, the angular deployment of the control surface <NUM> along the variable radius kinematic path is greater than the angular movement of the first and second cranks <NUM>, <NUM>. The space envelope of the actuation mechanism <NUM> is therefore comparatively smaller than for the actuation mechanisms <NUM> and <NUM>.

In addition, since the angular rotation of the coupling link <NUM> is in the opposite direction to the angular rotation of the first and second cranks <NUM>, <NUM>, the curved profile of the control surface <NUM> can be convex rather than concave as with the actuation mechanism <NUM>. By way of further explanation it can be seen that the first and second cranks of the actuation mechanism <NUM> rotate anticlockwise to deploy in the direction of the oncoming airflow A so the flow surface of the control surface <NUM> is concave to minimise the size of the aperture <NUM>. By contrast the first and second cranks of the actuation mechanism <NUM> rotate clockwise to deploy in the direction counter to the oncoming airflow A so the flow surface of the control surface <NUM> is convex to minimise the size of the aperture <NUM>. Of course, it will be appreciated that any of the actuation mechanisms <NUM>, <NUM>, <NUM> may be oppositely handed to suit either a convex or concave control surface <NUM>.

The actuation mechanism <NUM> may be actuated by an actuator coupled to either the first or second cranks in a similar manner to that described above for the actuation mechanisms <NUM>, <NUM>.

By deploying the aerodynamic control surface <NUM> along a curved kinematic path with variable radii, the deployment of the spoiler <NUM> can be tailored, e.g. to maximise the disruption to the oncoming airflow A. This is because the angle that the aerodynamic control surface <NUM> makes with the aerodynamic surface <NUM> at the aperture <NUM> is constantly changing because of the variable radii. The profile of the aerodynamic control surface <NUM> has a curvature which may match the path of variable curvature <NUM>, <NUM> so that the aperture <NUM> in the wing <NUM> has a width substantially the same as the maximum thickness T of the aerodynamic control surface <NUM>. Furthermore, the four-bar link mechanism <NUM>, <NUM> can be used to deploy the spoiler <NUM> in a smaller space in comparison to the actuator mechanism <NUM>, which needs a larger space to rotate the actuation mechanism <NUM>. Therefore, the four-bar link mechanism arrangement <NUM>, <NUM> can be utilised in wings with smaller spaces, such as high aspect ratio wings.

The aerodynamic control surface <NUM> can be actuated by the actuation mechanism <NUM>, <NUM>, <NUM> anywhere on the wing, such as the leading edge, mid-span, the trailing edge or the wing tip. The aerodynamic control surface <NUM> may be on arranged on an upper surface <NUM> or lower aerodynamic surface <NUM> of the wing <NUM>.

While the above examples have described in detail a single aerodynamic control surface <NUM> arranged to deploy from the wing <NUM>, it will be understood that multiple aerodynamic control surface <NUM> may be arranged on the wing <NUM>. Each aerodynamic control surfaces may be actuated simultaneously or independently by an actuation mechanism <NUM>, <NUM>, <NUM>. A plurality of actuation mechanisms may be coupled with each control surface and synchronised in their deployment. One actuator may control movement of several actuation mechanisms, or each actuation mechanism may have a respective actuator. Where a plurality of actuation mechanisms are connected to the same control surface, the type or arrangement of each actuation mechanism may differ, e.g. the number of linkages in each mechanism may be different, or the lengths of the linkages may be different. A linkage arrangement may be provided at each end of the control surface, optionally with one or more further linkages between the end linkages. The linkages may be tuned along the length of the control surface to provide a conical deployment, e.g. for a tapered wing or fuselage.

Whilst in <FIG> the control surface <NUM> is shown having a curved profile in the height dimension (to achieve the concave or convex flow surface) but a linear projection in the length dimension L, the control surface may instead be non-linear in the length dimension L.

As shown in <FIG>, the flow surface 20c and opposing surface 20d may be corrugated in the transverse direction (i.e. the length dimension L of the control surface transverse to the oncoming flow direction A) to create a corrugated profile <NUM>. In all other respects the control surface is the same as that shown in <FIG>. <FIG> show schematic plan views of the aerodynamic control surface <NUM> with different transverse profiles <NUM>.

The aerodynamic control surface <NUM> may have one or more curved corrugations, i.e. a non-linear curvature, and/or may have one or more vertexes along the length L. As shown in <FIG>, the aerodynamic control surface <NUM> may have a corrugated profile achieved by either vertexes 21a or a smooth curvature 21b. The number of corrugations in the aerodynamic control surface <NUM> may be varied depending on the location of the aerodynamic control surface, length of the aerodynamic control surface and the desired rigidity of the aerodynamic control surface. For example, <FIG> shows an aerodynamic control surface <NUM> with two corrugations (achieved through vertex 21a or smooth curvature 21b), while <FIG> shows a corrugated aerodynamic control surface with six vertexes 21a or smooth curvature 21b. It will be understood that any number of vertexes and/or curves (including one, to create a simple concave or convex transverse profile) may be used along the length L of the spoiler <NUM> to achieve a corrugated profile of the flow surface 20c and opposing surface 20d. The corrugated shape of the aerodynamic control surface <NUM> provides strength and rigidity to the aerodynamic control surface <NUM>. While the corrugated profile <NUM> of the aerodynamic control surface <NUM> has been described in relation to a single aerodynamic control surface <NUM>, it will be understood that multiple aerodynamic control surface <NUM> may be arranged adjacent along the length of the wing <NUM>. The aerodynamic control surface may be placed adjacent to each other at varying angles and orientations to achieve a corrugated profile along the span of the wing <NUM>.

In the case of a corrugated aerodynamic control surface <NUM>, the length of the linkages of the actuation mechanism <NUM>, <NUM> or <NUM> can be tailored depending on which part of the corrugated aerodynamic control surface <NUM> is rigidly fixed to the coupling link <NUM>, <NUM> to enable smooth deployment of the aerodynamic control surface from the retracted state <NUM> to the deployed state <NUM>.

The aerodynamic control surface <NUM> does not form part of the upper surface <NUM> of the wing <NUM>. That is to say, the flow surface 20c and opposing surface 20d do not form the upper surface <NUM>, (i.e. the aerodynamic profile) of the wing <NUM>. Instead, the aerodynamic control surface <NUM> moves from a retracted position <NUM> to an extended position <NUM> through an aperture <NUM> in the upper surface <NUM> of the wing <NUM>. <FIG> show a schematic plan view of the aperture <NUM> in the upper surface <NUM> of the wing <NUM>.

The aperture <NUM> has a width AW and a length AL. As the aerodynamic control surface <NUM> deploys through a curved kinematic path, the size of the aperture <NUM> matches the maximum thickness of the aerodynamic control surface <NUM>. That is to say, the width AW of the aperture <NUM> is substantially similar to the maximum thickness T of the aerodynamic control surface <NUM>. As shown in <FIG>, the aperture <NUM> may be slot-shaped, or as shown in <FIG>, the aperture <NUM> may be shaped to match the corrugated profile <NUM> of the spoiler <NUM>. While the aperture <NUM> is shown to be serpentine-shaped in <FIG>, it will be understood that the aperture <NUM> may be any suitable shape for a corrugated aerodynamic control surface <NUM> to extend through.

The actuating mechanisms <NUM>, <NUM> and <NUM> enable the aerodynamic control surface <NUM> to extend through a smaller aperture <NUM> in comparison to conventional flow control systems. The smaller aperture <NUM> reduces the drag effects over the upper surface <NUM> of the wing <NUM> when the aerodynamic control surface <NUM> is in the retracted position <NUM>. This is advantageous, as the combined movement of the actuation mechanism <NUM>, <NUM>, <NUM> and the profile of the aerodynamic control surface <NUM> results in a 'cleaner' aerofoil profile when the aerodynamic control surface <NUM> is in the retracted position <NUM>. That is to say, as the spoiler <NUM> does not form part of the upper surface <NUM> of the wing <NUM>, the aerodynamic profile of the wing <NUM> is not altered by any protrusions caused by aerodynamic control surface arranged on the wing <NUM>.

The distal end 20b of the spoiler may also include a seal <NUM> (shown in <FIG> and <FIG>). The seal extends along the entire length L of the aerodynamic control surface <NUM>. When the spoiler <NUM> is in the retracted state <NUM>, the seal <NUM> sits in the aperture <NUM> to seal the aperture. The seal <NUM> is dimensioned to be seated within the aperture <NUM> to form a smooth aerodynamic profile with the wing <NUM>. That is to say, the seal preferably does not protrude past the upper surface <NUM> of the wing <NUM>. The seal <NUM> therefore reduces any unwanted drag effects over the aperture <NUM>. The seal <NUM> may be made of an elastic material so that the seal <NUM> can deform to fully be seated in the aperture <NUM>. The seal <NUM> may any suitable cross-section to seal the aperture, such as a T-shape, top-hat, L-shaped or V-shaped. The seal <NUM> is secured to the distal end 20b of the aerodynamic control surface by any suitable means, such as adhesive.

In another example, the seal <NUM> may be made of a rigid material. The rigid seal may be integral with the control surface <NUM>. An elastomeric material may be provided around the aperture <NUM> when the seal <NUM> is made of a rigid material. Preferably, the seal is L-shaped or T-shaped such that when the aerodynamic control surface <NUM> is in the extended position <NUM>, the distal portion of the seal <NUM> (i.e. furthest from the flow surface) is parallel with the upper surface <NUM>. That is to say, the distal portion of the seal <NUM> is at right angles (or angled away) from the flow surface. This enables the seal <NUM> to act as a Gurney flap of the control surface when the control surface is deployed into the airflow. The Gurney flap may add power to the lift spoiling function of the control surface when deployed.

The aerodynamic control surface <NUM> is preferably a blade. That is to say, the aerodynamic control surface <NUM> is preferably made of a thin sheet or plate. The aerodynamic control surface <NUM> may be made of any suitable material, such as a metal, or composite material such as fibre reinforced matrix composite (e.g. carbon fibre reinforced plastic, CFRP). The thickness T of the aerodynamic control surface <NUM> can be any suitable thickness to withstand the oncoming airflow direction A. The control surface may be tapered with a taper of reducing thickness towards the cantilevered free end furthest from the actuation mechanism. The control surface may be reinforced with stiffeners.

<FIG> shows a cross-section of the wing <NUM> along line X-X in <FIG> which shows the aperture <NUM> in greater detail. The aperture <NUM> in the wing <NUM> is tapered towards the upper surface <NUM>. The aperture <NUM> has a first side wall 18c and a second side wall 18d. The first side wall 18c and second side wall 18d may be angled so that the aperture <NUM> is tapered. Alternatively, the side walls 18c and 18d may be generally parallel or may be curved. The walls of the aperture may be shaped to be just large enough to accommodate the kinematic path of the control surface deployment. In the example shown in <FIG>, the aperture <NUM> is tapered towards the upper surface <NUM> in the wing <NUM>. The aperture <NUM> has width 18A at the upper surface <NUM> that is larger than the width 18B at the opposite end of the aperture <NUM>. As the aerodynamic control surface <NUM> moves from the retracted position <NUM> to the deployed position <NUM>, the shape of the aperture <NUM> matches the curved kinematic path <NUM>, <NUM>, <NUM> of the aerodynamic control surface to avoid disrupting the path of the aerodynamic control surface <NUM>, and minimises any unnecessary space between the side walls 18c,18d of the aperture and the path of the spoiler <NUM>. While the side walls 18c and 18d of the aperture <NUM> is shown to be angled, it will be understood that only one side wall may be angled, or one or both of the side walls may be perpendicular to the surface <NUM>, or that the aperture <NUM> has a smaller width nearer the upper surface <NUM> of the wing <NUM>.

The aerodynamic control surface <NUM> may have a substantially constant thickness along the entire cross-section of the spoiler. Alternatively, the aerodynamic control surface <NUM> may be thicker at the end nearest the actuation mechanism, and thinner towards the cantilevered free end furthest from the actuation mechanism. The thickness of the aerodynamic control surface <NUM> can be tailored as required. The width AW of the aperture <NUM> has a width substantially same as the maximum thickness T of the aerodynamic control surface <NUM> so that the any gap between the first and second side wall 18c, 18d of the aperture in the upper surface <NUM> of the wing <NUM> and the spoiler <NUM> is reduced as the spoiler <NUM> moves from the retracted position <NUM> to the deployed position <NUM>.

The aircraft wing aerodynamic control surface <NUM> examples described above in detail are designed to provide lift reduction on airflow over the wing, but similar aerodynamic control surface may be attached to the lower aerodynamic surface <NUM> of the wing, as shown in <FIG>. The wing <NUM> may have both upper and lower surface aerodynamic control surface <NUM>.

Similarly, while the examples above are described in relation to a wing lift spoiling device, it will be understood that the aerodynamic control surface <NUM> may be any other type of device that controls the airflow over an aerodynamic surface, such as a spoileron, lift dumper, air brake of speed brake. As shown in <FIG>, the aerodynamic control surface <NUM> may be arranged on the fuselage <NUM>, or any other suitable aerodynamic surface, such as the tail <NUM>.

Whilst the examples above have been described in the context of an aircraft or aircraft, it will be appreciated that all examples of the control surfaces and the actuation mechanisms described may be used in any combination in other industries, e.g. on a wind turbine or a land vehicle, for example.

Claim 1:
An aerodynamic control surface assembly comprising:
a structure (<NUM>) with an aerodynamic surface (<NUM>);
an aerodynamic control surface (<NUM>) having a height dimension (H) and configured to move between an extended (<NUM>) and a retracted position (<NUM>), wherein the aerodynamic control surface has a curved profile in the height dimension;
an actuation mechanism (<NUM>, <NUM>) coupled to the aerodynamic control surface and configured to move the aerodynamic control surface between the extended and retracted positions,
wherein the aerodynamic control surface is arranged to deploy through an aperture (<NUM>) in the aerodynamic surface and into an oncoming airflow (A) over the aerodynamic surface when in the extended position and is arranged to retract out of the airflow when in the retracted position,
wherein the actuation mechanism is configured such that the control surface follows a curved kinematic path (<NUM>, <NUM>) as the control surface moves between the extended and retracted positions,
wherein the actuation mechanism remains fully behind the aerodynamic surface throughout the movement of the aerodynamic control surface between the extended and retracted positions, and characterised in that the curved kinematic path has variable radii along the path length.