Patent Description:
Leading edge slats are provided on aircraft wings to increase the lift provided by an aircraft wing during take off and/or landing. Leading edge slats are typically provided with a stowed position, in which the leading edge slat sits during normal flight operations, and a deployed position into which the leading edge slat is moved for take off and/or landing.

It is known to provide leading edge slats with seals, such that in the deployed position the leading edge slat is sealed against the main aerofoil structure of the wing. Such an arrangement is shown in <CIT>. Providing a sealed leading edge slat may reduce the drag created by the leading edge slat when in the deployed position, which may also reduce the noise generated during take off and/or landing, and also have fuel efficiency benefits. However, there are also benefits to unsealed leading edge slats, which may provide better stall control benefits than sealed leading edge slats. At present, the choice between a sealed leading edge slat and unsealed leading edge slat represents a compromise. <CIT> discloses an aircraft wing with a moveable leading edge slat and carrier tracks arranged to move the leading edge slat. <CIT> discloses an aircraft wing with a moveable leading edge slat which may cover a chine on the wing in a stowed position, and expose the chine in a deployed position. <CIT> discloses an aircraft wing with a moveable leading edge slat. <CIT> discloses an aircraft wing with a high lift generator including a lower surface plate of a slat which includes concave and convex portions. Those portions are shaped to generate eddies.

The present invention seeks to mitigate one or more of the above-mentioned problems.

According to a first aspect, the invention provides an aircraft wing comprising a leading edge slat and a fixed aerofoil portion, the leading edge slat moveable between a stowed position and deployed position, wherein in the deployed position a trailing edge of the leading edge slat comprises a sealed portion and an unsealed portion, the sealed portion forming a seal with the fixed aerofoil portion and the unsealed portion providing an airflow gap between the leading edge flap and the fixed aerofoil portion wherein the leading edge slat comprises an inboard end and an outboard end, the inboard end located towards the root of the aircraft wing and the outboard end located towards the tip of the aircraft wing, wherein the unsealed portion is located at the outboard end of the leading edge slat and the sealed portion is located at the inboard end of the leading edge slat and extends across at least <NUM>% of the trailing edge of the leading edge slat (<NUM>), and the leading edge slat is fully sealed against the fixed aerofoil portion when in the stowed position.

The sealed portion may extend across at least <NUM>%, <NUM>%, <NUM>%, or <NUM>%, of the trailing edge of the leading edge slat. The direction in which the seal portion extends may be spanwise along the leading edge slat.

The leading edge slat comprises an inboard end and an outboard end, the inboard end located towards the root of the aircraft wing and the outboard end located towards the tip of the aircraft wing. The unsealed portion is located at the outboard end of the leading edge slat.

The aircraft wing may comprise a seal located to provide the sealed portion of the leading edge slat. The seal may be situated on one or both of the leading edge slat and the fixed aerofoil portion. In an alternative arrangement, the sealed portion may simply comprise part of the leading edge slat and part of the fixed aerofoil portion remaining in contact, such that a sealed portion is provided.

The unsealed portion may comprise the trailing edge of the leading edge slat being manipulated to create the airflow gap. For example, the trailing edge of the leading edge slat may be stepped to create an airflow gap. Alternatively or additionally, the profile of the fixed aerofoil portion may be manipulated to create the airflow gap. For example, the profile of the fixed aerofoil portion may be stepped or reduced in order to create the airflow gap.

The leading edge slat is fully sealed against the fixed aerofoil portion when in the stowed position. By fully sealed it is meant that the leading edge slat is sealed along <NUM>% of the span of the leading edge slat. The aircraft wing may comprise a seal configured to seal the leading edge slat in the stowed position.

The unsealed portion may be configured to manipulate the airflow between the trailing edge of the leading edge slat and the associated portion of the fixed aerofoil structure. For example, the unsealed portion may comprise one or more vortex generators.

The unsealed portion may be located adjacent to, or proximate to, part of the aircraft wing which disrupts airflow. For example, such a part may be a wing tip device or a wing-mounted engine. The inventors have realised that the benefits of a sealed leading edge slat may be reduced or eliminated at wing locations such as at a wing tip device or engine mounting. Such locations may also be potential stall points for air flow. The provision of the unsealed portion adjacent to, or proximate to, such locations has been found to improve the stall characteristics proximate to local aircraft wing structures.

The deployed position may be a take-off position. There may be a further position in which the leading edge slat is deployed such that no seal is created between the leading edge slat and the fixed aerofoil portion. Such a position may be a landing position. The stowed position may be a "normal flight" position, for example the leading edge slat may be stowed during cruising flight of the aircraft.

According to a second aspect, the invention provides an aircraft comprising an aircraft wing according to the first aspect of the invention.

According to a third aspect, the invention provides a leading edge slat for an aircraft wing according to the first aspect of the invention.

The aircraft may be a passenger aircraft. The passenger aircraft may comprise a passenger cabin comprising a plurality of rows and columns of seat units for accommodating a multiplicity of passengers. The aircraft may have a capacity of at least <NUM>, at least <NUM> passengers, or at more than <NUM> passengers. The aircraft may be a powered aircraft. The aircraft may comprise an engine for propelling the aircraft. The aircraft may comprise wing-mounted, for example, underwing, engines.

The term 'or' shall be interpreted as 'and/or' unless the context requires otherwise.

<FIG> shows an aircraft <NUM>. The aircraft <NUM> comprises first and second aircraft wings <NUM>. As the aircraft wings <NUM> are mirrors of each other, only elements relating to a single wing <NUM> will be described. A skilled person will understand that the elements described with regards to one wing are found mirrored on the other wing <NUM>. The wing <NUM> comprises a main body <NUM> and a wing tip device <NUM>. The main body <NUM> is a conventional fixed aerofoil portion of the aircraft wing <NUM>. The wing tip device <NUM> may be movable to reduce the wing span of the aircraft <NUM>, or it may be fixed. Two under wing engines <NUM> are mounted to the wing <NUM>. A plurality of leading edge slats <NUM> are provided at the leading edge of the wing <NUM>. As is conventional, and would be easily understood by a skilled person, the leading edge slats <NUM> have a deployed position, in which they are moved forwards and often downwards relative to the overall wing <NUM>, such that they create a higher lift wing <NUM> than when the leading edge slats <NUM> are in a stowed position, flush with the overall wing <NUM>. The leading edge slats <NUM> are moved into the deployed position when taking off or landing the aircraft <NUM>, to allow a sharper angle of attack for those manoeuvres. Once the aircraft <NUM> has taken off and is climbing less steeply, or has entered a level flying state, the leading edge slats <NUM> are moved into the stowed position to reduce drag compared to the deployed position, thereby allowing more efficient flight. The leading edge slats <NUM> may remain in the stowed position during the initial stages of a descent, only being moved into the deployed position as the angle of descent increases to a certain value, or the speed of the aircraft is reduced sufficiently. Various different actuators and actuation methods may be used to move the leading edge slats <NUM> between the deployed and stowed positions, as would be well understood by the skilled person. As such, no further description of the actuators or actuation methods will be provided.

As can be seen, the leading edge slats <NUM> extend across the majority of the leading edge of the wing. This results in portions of the leading edge slats <NUM> being located proximate to potential stall points where airflow may be disrupted moving over the wing. Such points include proximate to the under wing engines <NUM> and where the wing tip device <NUM> joins the main body <NUM>. <FIG> shows a section of a leading edge slat <NUM>' that is located at the distal end of the wing <NUM>, at the point the wing tip device <NUM> joins the main body <NUM>. In <FIG> the leading edge slat <NUM>' is in the stowed position. <FIG> shows a perspective view of leading edge slat <NUM>' in the deployed position. The leading edge slat <NUM>' is divided into two portions, a sealed portion <NUM> and an unsealed portion <NUM>. When the leading edge <NUM>' is in the deployed position, the sealed portion <NUM> is sealed against the main body <NUM>. Sealed leading edge slats may provide advantages such as reduced drag compared to leading edge slats that are not sealed, reduced fuel consumption, and/or reduced noise. When the leading edge <NUM>' is in the deployed position, the unsealed portion is not sealed against the main body <NUM> and provides an airflow gap <NUM> between the leading edge <NUM>' and the main body <NUM>. The airflow gap <NUM> may result in an accelerated air flow through the airflow gap which results in improved airflow local to the airflow gap. However, as the airflow gap is only present at a specified part of the leading edge slat <NUM>' the benefits of providing a sealed leading edge slat are generally maintained. In the embodiment shown in <FIG>, it can be seen that the unsealed portion <NUM> is created by reduction in the chord of the leading edge slat <NUM>', such that in the deployed position the trailing edge of the leading edge slat <NUM>' does not make contact with the main body <NUM>. In contrast, the trailing edge of the sealed portion <NUM> of the leading edge slat <NUM>' does make contact with the main body <NUM> when in the deployed position. One or more seal strips or elements may be provided extending from the leading edge slat <NUM>' or the main body <NUM> to ensure a good seal between the sealed portion <NUM> of the leading edge slat <NUM>' and the main body <NUM>. Alternatively, the seal may be provided by direct contact between the leading edge slat <NUM>' and the main body <NUM>.

In order to maintain the benefits of a sealed leading edge slat, the unsealed portion <NUM> makes up a small proportion of the leading edge slat <NUM>'. For example, the unsealed portion may comprise around <NUM>% of the span of the leading edge portion <NUM>', with the remaining <NUM>% being made up by the sealed portion <NUM>. The skilled person will appreciate that the benefits of the invention may still result with the unsealed portion <NUM> making up from <NUM>% to <NUM>% of the span of the leading edge portion <NUM>' with the sealed portion <NUM> making up the remainder.

The leading edge slat <NUM>' is shaped such that when in the stowed position all of the trailing edge of the slat is sealed against the main body <NUM>. This may also require suitable shaping of the main body <NUM>, or the provision of distinct seal strips or elements, to allow this.

<FIG> shows an alternative embodiment, similar in substance to the embodiment described with reference to <FIG>. Where similar elements are provided, the same reference numerals have been used. The difference shown in <FIG> is that the unsealed portion <NUM> of the leading edge slat <NUM> further comprises three vortex generators <NUM>. The vortex generators may further improve the airflow at the point where the main body <NUM> meets the wing tip device <NUM>.

<FIG> shows a cross-sectional view, taken perpendicular to the front edge of the leading edge slat, of a sealed portion of a wing according to the first embodiment of the invention. The initial view shows the stowed position and how the leading edge slat <NUM>' is located relative to the main body <NUM>. The second view shows the leading edge slat <NUM>' in a deployed take-off position. The trailing edge of the leading edge slat <NUM>' remains in contact with the main body <NUM>. The third view shows the leading edge slat <NUM>' in a deployed landing position. In this case, the trailing edge of the leading edge slat is not in contact with the fixed aerofoil portion, the leading edge slat <NUM>' having been extended beyond the deployed take-off position.

<FIG> shows a cross-sectional view, taken perpendicular to the front edge of the leading edge slat, of an unsealed portion of a wing according to the first embodiment of the invention. The initial view shows the leading edge slat in a stowed position, with the trailing edge of the leading edge slat <NUM>' in contact with the main body <NUM>. The second view shows the leading edge slat in a deployed take-off position, with a clear gap between the trailing edge of the leading edge slat <NUM>' and the main body <NUM>. In this case, the main body <NUM> has a consistent cross-section across the whole length of the leading edge slat <NUM> and the leading edge slat <NUM> includes a removed section in order to provide the unsealed portion. A consistent cross-section does not imply that the cross-section is identical, as the main body will taper in size as it moves out in a span wise direction, rather a consistent cross-section means that that any such taper is smoothly graduated. The third view shows the leading edge slat <NUM> in a deployed landing position. As in <FIG>, there is a clear gap between the trailing edge of the leading edge slat <NUM>' and the main body <NUM>.

<FIG> shows a cross-sectional view, taken perpendicular to the front edge of the leading edge slat, of an unsealed portion of a wing according to a second embodiment of the invention. In this embodiment, the unsealed portion is created by shaping the main body <NUM> to provide a gap between the main body and the leading edge flap <NUM>. The dashed line represents the cross-sectional profile of the main body <NUM> across the sealed portion of the leading edge slat <NUM>, and is as shown with reference to <FIG>. It can be seen that in the take-off position, the trailing edge of the leading edge slat <NUM> remains in contact with the main body <NUM>. As can be better seen in <FIG>, the trailing edge of the leading edge slat <NUM> is consistently shaped across the whole of the length of the leading edge slat <NUM>, in contrast to the first embodiment. The initial view shows the leading edge slat in a stowed position, with the trailing edge of the leading edge slat <NUM> in contact with the main body <NUM>. The second view shows the leading edge slat in a deployed take-off position, with a clear gap between the trailing edge of the leading edge slat <NUM> and the main body <NUM>. The third view shows the leading edge slat <NUM> in a deployed landing position. As in <FIG>, there is a clear gap between the trailing edge of the leading edge slat <NUM> and the main body <NUM> when in the deployed landing position.

<FIG> show a plan view of the first embodiment of the invention along with cross-sectional views taken along a first line A-A, showing the unsealed portion, and a second line B-B, showing the sealed portion. The leading edge portion <NUM>' is in the deployed position. The plan view in <FIG> shows the leading edge slat in the deployed take-off position, and the arrows indicate the airflow which passes through the unsealed portion.

<FIG> show a plan view of the second embodiment of the invention along with cross-sectional views taken along a first line A-A, showing the unsealed portion, and a second line B-B, showing the sealed portion. The leading edge portion <NUM> is in the deployed position. The plan view in <FIG> shows the leading edge slat in the deployed take-off position, and the arrows indicate the airflow which passes through the unsealed portion.

Alternative arrangements may be provided, as will be appreciated by a skilled person. In an example which is not covered by the appended claims, the leading edge slat may be located such that the unsealed portion is proximate to an alternative part of the wing. Such a location may be proximate to an underbody engine <NUM>.

Claim 1:
An aircraft wing (<NUM>) comprising a leading edge slat (<NUM>) and a fixed aerofoil portion (<NUM>), the leading edge slat (<NUM>) moveable between a stowed position and deployed position, wherein in the deployed position a trailing edge of the leading edge slat (<NUM>) comprises a sealed portion (<NUM>) and an unsealed portion (<NUM>), the sealed portion (<NUM>) forming a seal with the fixed aerofoil portion (<NUM>) and the unsealed portion (<NUM>) providing an airflow gap between the leading edge slat and the fixed aerofoil portion (<NUM>), wherein the leading edge slat (<NUM>) comprises an inboard end and an outboard end, the inboard end located towards the root of the aircraft wing (<NUM>) and the outboard end located towards the tip of the aircraft wing (<NUM>), wherein the unsealed portion is located at the outboard end of the leading edge slat (<NUM>), and the sealed portion is located at the inboard end of the leading edge slat and extends across at least <NUM>% of the trailing edge of the leading edge slat (<NUM>) and the leading edge slat (<NUM>) is fully sealed against the fixed aerofoil portion (<NUM>) when in the stowed position.