Patent Description:
Aircraft lifting surfaces have a span direction and a chord direction. They comprise a stationary part and they may comprise one or more movable parts.

The stationary part is stationary with respect to the rest of the aircraft, for instance, with respect to the fuselage. The stationary part may be a central or torsion box.

The movable part is movable with respect to the stationary part of the lifting surface. The movable part may be one or more control surfaces.

Movable parts are movable with respect to stationary parts between at least a first position and a second position. Movable parts may have a rotation movement around an axis or they may have a translation and rotation movement.

For aircraft lifting surfaces, empennage lifting surfaces and wing surfaces are known.

Empennage lifting surfaces comprise control surfaces that are rigid structures that are movable with respect to a central torsion box of the lifting surface. Specifically, the movement of the control surfaces comprises a rotation of the control surface around a hinge axis in the span direction.

Control surfaces are moved by hydraulic, electric or hybrid actuators located in the aircraft lifting surface. The actuator may produce a displacement of the control surface such that the lifting surface extends to increase the lifting area. In another embodiment, the control surface may rotate around a hinge axis. This rotation produces a change in angle of the control surface resulting in an increase of camber of the aircraft lifting surface profile. This increase of camber produces the desired lift increase.

The actuation system and the hinges are located rearward of a rear spar of the torsion box which is normally located around at <NUM>% of the chord. Around <NUM>% of the chord of the profile is required for the installation of the actuator and hinge, so only the remaining <NUM>% of the chord is available for the control surface itself.

The space between the rear spar and the control surface, where the actuator and the hinge are located, is covered by a rigid aerodynamic fairing. These rigid fairings cannot deform, so they are not able to contribute to increase the camber of the profile, and, as a consequence, to increase the lift of the lifting surface.

The control surfaces of a wing lifting surface are more complex than empennage ones. In this case the structure of the wing is the main body producing lift. The control surfaces produce both an increase of camber and an increase of chord on the aircraft lifting surface profile so that an increased lift performance is achieved.

Control surfaces may be located at the leading edge and/or at the trailing edge of the aircraft lifting surface.

According to the above, the most efficient lifting surface is achieved when the control surfaces are located at the same time on the trailing edge and on the leading edge and producing a change of camber and an increase of chord.

It is also known to locate the rotation axis outside the aircraft lifting surface to achieve the desired combination of translation and rotation. By rotating around the mentioned axis, the control surface achieves at the same time an increase of incidence angle and a translation in the chord direction. When the rotation axis is located outside the aerodynamic profile of aircraft lifting surface it requires one or multiple actuators and a heavy support structure for these actuators. For this reason, it needs to be covered by additional fairings. For instance, for several conventional flaps located in wings, multiple support structures and fairings are located along the span of the wing. As previously stated, said fairings are located outside the aerodynamic profile of the lifting surface resulting in a significant weight increase and drag penalty.

The prior art is illustrated by document <CIT> disclosing a lift flap bearing apparatus, a lift flap assembly, an airfoil and an aircraft.

Prior art document <CIT> proposes an aircraft with reduced environmental impact. It discloses an acoustic masking device comprising a masking element, such as a flap, which can move between a position in which it is retracted into the wing, and a position in which it is extended toward the rear of the wing.

Further prior art documents are <CIT>, <CIT>, <CIT> and <CIT> that disclose known flap mechanisms.

The proposed invention consists of an aircraft lifting surface comprising at least one actuation system that allows the movement of the movable part with respect to the stationary part of the lifting surface with a simple system and easy to adapt to current aircraft lifting surfaces.

An aircraft lifting surface object of the invention comprises:.

The end of the movable part is the portion where the movable part begins and is located in a position adjacent to the root of the lifting surface, i.e., adjacent to the fuselage of the aircraft. A second end of the movable part may be located at the tip of the lifting surface or, in an alternative, at an intermediate position along the span of the aircraft lifting surface. Intermediate position is understood as located in a span position between the root and the tip of the lifting surface.

The actuation system of the aircraft lifting surface of the invention comprises a sliding system causing the movable part to slide with respect to the stationary structure. The sliding system is joined to:.

The stationary structure is located adjacent to the end of the movable part, for instance, adjacent to a control surface. The stationary structure may be located in a plane perpendicular to the span direction of the movable part. The stationary structure is also located adjacent or, what is the same, nearby and immediately following the movable part in the span direction.

The sliding system may be of the kind that comprises a guide track and a complementary element. The guide track and the complementary element are configured to move relative to each other. The complementary element may be movable along the guide track or, alternatively, the guide track may be movable with respect to a static complementary element. The complementary element may be a bearing wheel, a pin, etc,
The sliding system is joined to the end of the movable part on one side and to the stationary structure on the other side. It means that the sliding system may be located between the end of the movable part and the stationary structure or in an alternative, the guide track and/or the complementary element may be located in a recess at the end of the movable part and/or at the stationary structure. In another alternative, the shape of the end of the movable part may act as a guide track.

According to the above, the movable part and the stationary structure are in movable coupling by the sliding system.

Therefore, the movable part, the stationary structure and the sliding system are configured so that the relative movement of the complementary element and the guide track forces the movable part to follow the guide track so that the movable part is moved with respect to the stationary structure between at least a first position and a second position.

Attending to the shape of the guide track of the sliding system, the actuation system may generate a rotation and/or translation in the movable part. If both movements are achieved, it results in an increase of camber and an increase of the chord of the profile with minimum intermediate supports.

The movable part is forced to follow the track shape between at least a first and a second position, for instance, a forward and a rear position separated by a longitudinal distance. On those positions the reaction of the track produces a force normal to the track. In each instant of the movement of the movable part, the projection of the normal reaction to the track, in a plane close to the perpendicular to the span of the lifting surface, can be either parallel, so that the resultant displacement will be a pure translation, or they can intersect at a point, so that the resultant displacement of the movable will be a rotation about those intersections.

The lifting surface objects of the invention provide the following advantages:.

Therefore, the actuation system object of the invention provides additional structure efficiency and reduces aerodynamic drag.

It has to be noted that in this application by aircraft lifting surface it is understood a wing, a vertical tail plane or a horizontal tail plane, or any other aerodynamic surface that may provide significant lift or maneuverability to the aircraft.

To complete the description and to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate preferred embodiments of the invention. The drawings comprise the following figures.

<FIG> shows a perspective view an embodiment of an aircraft showing the different aircraft lifting surfaces (<NUM>) and their control surfaces or movable parts (<NUM>). The invention can be applied, for instance in a wing (<NUM>), a vertical tail plane (<NUM>) or a horizontal tail plane (<NUM>).

The shown lifting surfaces (<NUM>) have a span direction and a chord direction and comprise a central box as stationary parts (<NUM>) and control surfaces as movable parts (<NUM>). The movable parts (<NUM>) can be located at the leading edge, trailing edge or at both. The movable parts may be ailerons, elevators, rudders, spoilers, flaps or slats, among others.

Movable parts (<NUM>) are movable with respect to the central box of the aircraft lifting surface (<NUM>). Movable parts (<NUM>) can be moved towards different positions, at least between a first position and a second position.

Movable parts (<NUM>) comprise at least an end (<NUM>) in the span direction. Depending on the length and position of the movable part (<NUM>), the end (<NUM>) of the movable part (<NUM>) may be located at the root of the lifting surface (<NUM>), at the tip of the lifting surface (<NUM>) or at an intermediate position along the span direction of the lifting surface (<NUM>) located between the root and the tip of the lifting surface (<NUM>).

<FIG> discloses an embodiment of the actuation system. The depicted system comprises:.

In this way, the movement of the complementary element (<NUM>) along the guide track (<NUM>) forces the movable part (<NUM>) to follow the guide track (<NUM>) so that the movable part (<NUM>) is moved with respect to the stationary structure (<NUM>) between at least a first position and a second position.

More particularly, the stationary structure (<NUM>) comprises a slot (<NUM>) housing the guide track (<NUM>). The end (<NUM>) of the movable part (<NUM>) comprises the complementary element (<NUM>) such that the complementary element (<NUM>) is configured to fit in the slot (<NUM>) to follow the guide track (<NUM>).

In this embodiment, the complementary element (<NUM>) comprises at least one rolling element (<NUM>) adapted to roll in the guide track (<NUM>). The complementary element (<NUM>) also comprises a shaft joined to the movable part (<NUM>). The rolling element (<NUM>) is adapted to rotate around the shaft.

More particularly, the end (<NUM>) of the movable part (<NUM>) comprises a set of shafts and rolling elements (<NUM>) that may contact the guide track (<NUM>). The guide track (<NUM>) is structurally attached to the stationary structure (<NUM>) of the aircraft and has the required curved shape to force the rolling element (<NUM>) to follow a predetermined path.

Alternatively, the guide track (<NUM>) may be located at the end (<NUM>) of the movable part (<NUM>) and the complementary element (<NUM>) may be located in the stationary structure (<NUM>).

The above embodiment is disclosed in <FIG>. In this embodiment, the stationary structure (<NUM>) comprises at least a first and a second complementary element (<NUM>). In the shown embodiment, the stationary structure (<NUM>) comprises several rolling elements (<NUM>). The end (<NUM>) of the movable part (<NUM>) forms the guide track (<NUM>) by, for instance, a curved shape of the movable part (<NUM>). The end (<NUM>) of the movable part (<NUM>) is configured to be located between the first and the second complementary elements (<NUM>) so that the end (<NUM>) of the movable part (<NUM>) is adapted to move relative to the first and the second complementary elements (<NUM>) in a curved manner.

In the embodiment, the complementary element (<NUM>) comprises a set of rolling elements (<NUM>) such that the end (<NUM>) of the control surface or movable part (<NUM>) rolls between them. More specifically, the end (<NUM>) of the movable part (<NUM>) is located between a first row and a second row of complementary rolling elements (<NUM>).

In the above embodiment, the end (<NUM>) of the movable part (<NUM>) is a male guide track (<NUM>), contrary to the embodiment disclosed in <FIG> in which the guide track (<NUM>) located in the stationary structure (<NUM>) acts as a female guide track (<NUM>).

The guide track (<NUM>) may comprise a rectilinear portion, a linear portion or both.

A rectilinear portion would impart the movable part (<NUM>) with a translation in the chord direction with respect to the stationary part (<NUM>). It is partly shown in the left side of <FIG>.

<FIG> and the right side of <FIG> show a curved portion such that the movement of the movable part (<NUM>) with respect to the stationary part (<NUM>) is a rotation around an axis (<NUM>) located in the span direction.

In the embodiments shown in <FIG>, the complementary element (<NUM>) comprises a rolling element (<NUM>) and a shaft.

<FIG> discloses an actuator (<NUM>) in connection with the movable part (<NUM>) and the stationary part (<NUM>) to impart a force to the movable part (<NUM>) for its movement between a first position and a second position with relation to the stationary part (<NUM>).

The actuator (<NUM>) is located in the portion (<NUM>) of the fuselage.

The advantage of allocating the actuator (<NUM>) in the fuselage is that it does not require space inside the aerodynamic profile of the lifting surface (<NUM>) reducing the available space for, for instance, the torsion box.

In a configuration that is not covered by the claims, the actuator (<NUM>) may be located in the movable part (<NUM>).

The shown actuator (<NUM>) is a linear actuator having a longitudinal axis. The longitudinal axis is approximately tangent to the curve described by the guide track (<NUM>). The extension and retraction of the actuator (<NUM>) produces a displacement of the end (<NUM>) of the movable part (<NUM>) along the guide track (<NUM>).

This would make the efforts to move the movable part (<NUM>) as minimal as possible.

In an embodiment, the portion of the movable part (<NUM>) fitting the fuselage through a slot (<NUM>) comprises attaching means, for instance, lugs, axis and bearings, to which the actuator (<NUM>) is attached.

An actuation system may also be applied to an end (<NUM>) of a movable part (<NUM>) located at the tip of the lifting surface (<NUM>) and/or at an intermediate position of the lifting surface (<NUM>).

According to the invention, the stationary structure is a portion (<NUM>) of the fuselage of the aircraft and the end (<NUM>) of the movable part (<NUM>) is located in a root of the aircraft lifting surface (<NUM>) in the span direction.

An end (<NUM>) of the movable part (<NUM>) may be located at the tip of the aircraft lifting surface (<NUM>) in the span direction with a stationary structure being a fairing adjacent to the end (<NUM>) of the movable part (<NUM>) at the tip of the lifting surface (<NUM>) and connected to the stationary part (<NUM>). The wing tip fairing may for example be a wing tip plate or a wing tip fence.

As in the embodiment shown in <FIG>, at the tip of the lifting surface (<NUM>) the movable part (<NUM>) comprises an end (<NUM>) that fits in a slot (<NUM>) of the wing tip fairing (<NUM>), said fairing forming a stationary structure of the lifting surface (<NUM>).

Another option is that an end (<NUM>) of the movable part (<NUM>) is located at an intermediate position along the span of the lifting surface (<NUM>). A stationary structure may comprise a fairing in the vicinity of the end (<NUM>) of the movable part (<NUM>) at said intermediate position along the lifting surface. The movable part (<NUM>) may be joined to such intermediate stationary part (<NUM>).

In an embodiment, actuation systems may be applied to two ends (<NUM>) in the span direction of the movable part (<NUM>). The movable part (<NUM>) would comprise a second end in the span direction and the sliding system would comprise a second sliding system joined to the second end of the movable part and configured to be joined to a stationary structure of the aircraft.

Said second end (<NUM>) may be located at the tip of the lifting surface (<NUM>) and/or at an intermediate position of the lifting surface (<NUM>).

Claim 1:
Aircraft lifting surface (<NUM>) having a span direction, the lifting surface (<NUM>) comprising:
- a stationary part (<NUM>),
- a movable part (<NUM>), movable with respect to the stationary part (<NUM>) and comprising an end (<NUM>) in the span direction,
- a portion (<NUM>) of a fuselage of an aircraft,
- an actuation system configured to actuate the movable part (<NUM>) with respect to the stationary part (<NUM>),
the actuation system comprising a sliding system joined to:
- the end (<NUM>) of the movable part (<NUM>), and
- joined to a stationary structure of the aircraft, said stationary structure being:
• located adjacent in the span direction to the end (<NUM>) of the movable part (<NUM>), and
• connected with the stationary part (<NUM>) of the lifting surface,
so that the sliding system allows the movable part (<NUM>) to slide with respect to the stationary structure, the stationary structure being the portion (<NUM>) of the fuselage of the aircraft and the end (<NUM>) of the movable part (<NUM>) being located at a root of the aircraft lifting surface (<NUM>) in the span direction, characterized by an actuator (<NUM>) located in the portion (<NUM>) of the fuselage and in connection with the movable part (<NUM>), the actuator (<NUM>) being configured to impart a force to the movable part (<NUM>) for its movement between at least a first position and a second position.