Aircraft empennage surface and aircraft

Abstract

The present invention relates to an aircraft empennage surface and an aircraft, and more particularly to a configuration of an aircraft empennage surface having a single projection for improving airflow control without or without loss of resistance negligible.

Description

Technical Field

[0001] The present invention relates to an aircraft fin surface and, more particularly, to a configuration of an aircraft fin surface having a single protrusion for improving air flow control without or with negligible drag loss. Background Art

[0002] The performance of aircraft fin surfaces, such as horizontal and vertical fin planes, is an important issue in global aircraft design because these surfaces are used to control the aircraft and must provide stabilizing forces under a range of challenging flight and environmental conditions.

[0003] A known configuration that affects the aerodynamics of fin surfaces is the vortex generator. Vortex generators are typically small protrusions spanning the air flow, usually placed on the low-pressure side of the airfoil of the fin surface. Some vortex generators are referred to as "dog teeth" and "notches" and are arranged on the leading edge of the fin surface.

[0004] Vortex generators generally represent discontinuities that generate vortices. The purpose of these vortex generators is to generate vortices in a controlled and predictable manner. Vortices are generally undesirable because they generate drag, but the vortices generated by these devices are beneficial because they delay wing stall. Stall occurs when the wing reaches a high enough angle of attack such that the air flow separates from its surface. This flow separation results in a rapid loss of lift and the aircraft may become uncontrollable. These vortices help to maintain the boundary layer of the flowing air attached to the wing.

[0005] Dog teeth and notched leading edges work in a similar manner to increase the flow velocity above a portion of the wing and delay stall. The difference between these devices lies in the strength of the vortices generated by each device, the conditions under which the vortices are formed, and the area of the wing affected by the vortex. Vortex generators are typically used in series to generate multiple small vortices above most of the wing. Dog teeth also generate a single strong vortex, and notches typically generate a pair of strong vortices, one from each edge of the notch.

[0006] Another example of a known configuration is fences and vortex diffusers. Fences are most commonly used as devices to control spanwise flow on swept wings. This type of flow occurs when the air flowing over a swept wing moves outward towards the wing tip as it travels along the wing. This movement is undesirable because it typically causes flow separation on the outer surface of the wing, resulting in a loss of aileron control effectiveness. The purpose of a fence is to redirect the flow back towards the trailing edge. Another benefit of a fence is that it can be used to generate vortices to locally increase the flow velocity and delay separation.

[0007] The vortex generators serve the same purpose on the lower surface of the wing and for this reason the device is often referred to as an underwing fence. Like traditional boundary layer fences, vortex generators can also be used to generate vortices on the lower side of the wing at low angles of attack. However, the vortex generators are more useful at large angles when a second vortex wraps around the leading edge and travels above the upper surface of the wing. This vortex helps to delay separation above the upper surface.

[0008] Most of the above configurations are typically seen on military aircraft, especially high-performance fighter jets. Leading edge extensions, dog teeth, and fences are particularly common on these aircraft because these devices increase the stall angle of attack and improve maneuverability. These modifications are rarely seen on commercial airliners that do not require excellent maneuverability. However, conventional vortex generators are very common on airliners to increase the effectiveness of flaps and other control surfaces during takeoff and landing. In any case, all of these vortex generating configurations provide a high drag penalty during cruise due to local flow separation.

[0009] Accordingly, different configurations have been designed in recent years to improve the performance of the aircraft empennage surface. The present invention provides a new and improved configuration for an aircraft empennage surface that optimizes its safety, performance, and maintenance and provides further related advantages. Summary of the Invention

[0010] The present invention provides an aircraft empennage surface according to one aspect and an aircraft according to another aspect. In other aspects of the present invention, embodiments of the present invention are defined.

[0011] In a first aspect of the invention, the present invention provides an aircraft empennage surface that includes a leading edge, a trailing edge, a tip, and a root, wherein the aircraft empennage surface further includes a single protrusion that projects from the leading edge, wherein the protrusion:

[0012] projects only in a direction opposite to the trailing edge from the leading edge, and the protrusion is positioned closer to the tip than to the root; and

[0013] includes a first lateral side and a second lateral side, the first lateral side and the second lateral side originating from different points along the wingspan of the empennage wing, the points not coinciding with the tip or the root; wherein the first lateral side is closer to the tip than the second lateral side;

[0014] and wherein the protrusion is entirely located within a section of the leading edge that includes between 50% and 95% of the wingspan measured from the root.

[0015] The present invention provides a modification to the fin surface based on a single protrusion protruding from the leading edge of the fin surface. That is, the present invention proposes to place only one protrusion as a flow control device that protrudes from the leading edge in the aircraft fin surface for enhancing the airflow control on the aircraft fin surface.

[0016] Specifically, the protrusion is arranged to protrude only in a direction opposite to the trailing edge from the leading edge. Additionally, the protrusion is closer to the tip than to the root.

[0017] The single protrusion includes two lateral sides, namely a first lateral side and a second lateral side. These lateral sides originate from different points along the fin span of the leading edge. The points from which the lateral sides originate do not coincide with the tip or the root of the aircraft fin surface. Moreover, the first lateral side is closer to the tip than the second lateral side.

[0018] Furthermore, the protrusion is entirely located in the section of the leading edge that includes between 50% and 95% of the fin span from the root. These percentages of the fin span correspond to the respective intersections between each lateral side of the protrusion and the leading edge. That is, the points on the leading edge from which the lateral sides of the protrusion originate are included in the said fin span range (50% to 95%) from the root, where position 0% corresponds to the root. In other words, the entire protrusion including the intersections of the lateral sides of the protrusion and the leading edge falls within the said fin span range.

[0019] In an embodiment, the protrusion is entirely located in the section of the leading edge that includes between 60% and 80% of the fin span from the root. In an embodiment, the point on the leading edge from which the second lateral side originates is located at one of the following positions: 66.6% and 75% of the fin span from the root.

[0020] Compared with prior art solutions such as fin surfaces without protrusions or with multiple protrusions, the aircraft fin surface including a single protrusion in this fin span section provides better performance in a series of aircraft fin metrics such as lateral force and drag versus sideslip angle. Advantageously, the protrusion provided in the fin surface improves the airflow control of the fin surface and achieves a greater surface control force, which allows reducing the aircraft fin weight and size, thereby resulting in enhanced fuel efficiency, material savings, and reduction of carbon emissions.

[0021] More specifically, setting such a protrusion on the aircraft fin surface provides a greater lateral force coefficient within the sideslip angle range while having a minimal adverse effect on the drag coefficient. The level of performance improvement in the lateral force coefficient is approximately 5% compared to the same aircraft fin surface without a protrusion.

[0022] In an embodiment, the first lateral side and the second lateral side of the protrusion converge at the tip of the protrusion. The tip of the protrusion is the part of the protrusion that is furthest from the leading edge.

[0023] In an embodiment, the fin surface of the aircraft is a swept surface or a forward-swept surface. In an embodiment, the first lateral side of the protrusion is longer than the second lateral side of the protrusion, or the second lateral side of the protrusion is longer than the first lateral side of the protrusion, or the first lateral side and the second lateral side of the protrusion have the same length. Specifically, for a swept surface, the first lateral side, i.e., the lateral side of the protrusion closer to the tip, is longer than the second lateral side, i.e., the lateral side closer to the root. However, for a forward-swept surface, the second lateral side is longer than the first lateral side.

[0024] In an embodiment, the first lateral side and / or the second lateral side of the protrusion is curved.

[0025] In an embodiment, the first lateral side and / or the second lateral side includes a convex shape.

[0026] In an embodiment, the protrusion includes a sinusoidal shape. In another embodiment, the protrusion includes a serrated shape. In other words, the combination of the lateral sides of the protrusion and the tip of the protrusion has a sinusoidal shape or a serrated shape.

[0027] In an embodiment, the first lateral side and the second lateral side of the protrusion are integrated into the leading edge of the fin surface by fitting with a smooth curve in terms of geometric configuration. This configuration improves the aerodynamics on the fin surface of the aircraft.

[0028] In an embodiment, the distance that the protrusion protrudes from the leading edge is between 4% and 12% of the mean aerodynamic chord of the fin surface of the aircraft.

[0029] In an embodiment, the protrusion extends along the fin span between 4% and 12% of the fin span, between the tip and the root, and preferably between 6% and 9% of the fin span. The extension of the protrusion along a% of the fin span will be understood as the length between the corresponding points of the leading edge from which the protrusion or the lateral sides of the protrusion originate. Therefore, the protrusion of this embodiment is very small relative to the fin span of the fin surface, and thus, the protrusion provides a greater lateral force coefficient within the range of sideslip angles, while having a minimal adverse effect on the drag coefficient, thereby allowing a possible reduction in the size of the fin surface of the aircraft, and this can lead to a weight reduction. These advantages contribute to improving fuel consumption without sacrificing the performance of the aircraft.

[0030] In an embodiment, the fin surface of the aircraft is a horizontal fin surface. In another embodiment, the fin surface of the aircraft is a vertical fin surface.

[0031] In an embodiment, the aspect ratio of the protrusion is included between 0.8 and 1.2, and preferably the aspect ratio of the protrusion is 1. In other words, the ratio between the length and the width of the protrusion is included between 0.8 and 1.2, and preferably this ratio is 1. The length of the protrusion is determined by the distance that the protrusion protrudes from the leading edge of the fin surface towards the tip of the protrusion. The width of the protrusion is determined by the maximum distance between the first lateral side and the second lateral side of the protrusion.

[0032] In a second aspect of the invention, the invention provides an aircraft comprising at least one fin surface of an aircraft according to the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In view of the detailed description of the invention that becomes apparent from the preferred embodiments of the invention, these and other features and advantages of the invention will be clearly understood. Referring to the drawings, the preferred embodiments are given only by way of example and are not limited thereto.

[0034] Figure 1 : The figure shows a schematic view of a fin surface of an aircraft according to an embodiment of the invention.

[0035] Figure 2 : The figure shows a schematic view of a fin surface of an aircraft according to an embodiment of the invention.

[0036] Figures 3A to 3E : The figures show different embodiments of the fin surface of an aircraft according to the invention.

[0037] Figure 4A : The figure shows a graph comparing the side force coefficient of a fin surface of an aircraft according to an embodiment of the invention with the side force coefficient at a rudder angle of 0°.

[0038] Figure 4B : The figure shows a graph comparing the drag coefficient of a fin surface of an aircraft according to an embodiment of the invention with the drag coefficient at a rudder angle of 0°.

[0039] Figure 5A : The figure shows a graph comparing the side force coefficient of a fin surface of an aircraft according to an embodiment of the invention with the side force coefficient at a rudder angle of 10°.

[0040] Figure 5B : The figure shows a graph comparing the drag coefficient of a fin surface of an aircraft according to an embodiment of the invention with the drag coefficient at a rudder angle of 10°.

[0041] Figure 6A: This figure shows a graph comparing the side force coefficient of the aircraft fin surface according to an embodiment of the present invention with the side force coefficient at a rudder angle of 20°.

[0042] Figure 6B : This figure shows a graph comparing the drag coefficient of the aircraft fin surface according to an embodiment of the present invention with the drag coefficient at a rudder angle of 20°.

[0043] Figure 7A : This figure shows a graph comparing the side force coefficient of the aircraft fin surface according to an embodiment of the present invention with the side force coefficient at a rudder angle of 30°.

[0044] Figure 7B : This figure shows a graph comparing the drag coefficient of the aircraft fin surface according to an embodiment of the present invention with the drag coefficient at a rudder angle of 30°.

[0045] Figure 8 : This figure shows a schematic diagram of an aircraft according to an embodiment of the present invention. Detailed Embodiments

[0046] Figure 1 and Figure 2 show the aircraft fin surfaces according to two embodiments of the present invention. Figure 1 and Figure 2 show the vertical fin surface 1, and according to each figure, the vertical fin surface 1 is provided with only one protrusion 3, but the protrusion is located at different points along the leading edge 2 of the vertical fin surface 1. Both figures show that the vertical fin surface 1 includes a leading edge 2 having a tip 2.1 and a root 2.2 and a trailing edge 5 opposite to the leading edge 2.

[0047] As described above, Figure 1 and Figure 2 these vertical fin surfaces 1 also include a single protrusion 3 protruding from the leading edge 2. Specifically, the protrusion 3 protrudes only in the direction opposite to the trailing edge 5 as a surface continuation of the vertical fin surface 1.2. In Figure 1 and Figure 2 both, the protrusion 3 is placed closer to the tip 2.1 than to the root 2.2. In addition, Figure 1 the protrusion 3 shown in Figure 2 is closer to the tip 2.1 than the protrusion 3 shown in

[0048] These Figure 1 and Figure 2The protrusion 3 shown in [description] includes a first lateral side 3.1 and a second lateral side 3.2. The first lateral side 3.1 is closer to the tip 2.1 than the second lateral side 3.2. Each of the first lateral side 3.1 and the second lateral side 3.2 originates from a point on the leading edge 2 along the wingspan of the vertical tail. These points do not coincide with each other and do not coincide with the tip 2.1 or the root 2.2 either. In addition, the protrusion 3 is entirely located in the section of the leading edge 2 that is between 50% and 95% of the wingspan of the vertical tail measured from the root 2.2. That is, both the intersection point of the first lateral side 3.1 and the leading edge 2 and the intersection point of the second lateral side 3.2 and the leading edge 2 are located within the range of 50% to 95% of the above-mentioned wingspan of the vertical tail.

[0049] According to these Figure 1 and Figure 2 In the embodiment shown in [description], the first lateral side 3.1 of the protrusion 3 is longer than the second lateral side 3.2. Additionally, the two lateral sides 3.1, 3.2 converge at the tip 3.3 of the protrusion and are curved. As can be observed in these figures, the first lateral side 3.1 and the second lateral side 3.2 have a convex shape.

[0050] In Figure 1 and Figure 2 In the embodiments shown in [description], the distance by which the protrusion 3 protrudes from the leading edge 2 is between 4% and 12% of the main aerodynamic chord of the vertical tail surface 1.2. Additionally, in these embodiments, the protrusion extends along the wingspan of the vertical tail between 6% and 9% of the wingspan of the vertical tail surface 1.2.

[0051] In the embodiment in which the aircraft tail surface 1 is the vertical tail surface 1.2, the protrusion protrudes 7.56% of the average aerodynamic chord of the vertical tail plane from the leading edge 2, extends 7.5% along the wingspan, and is located in the leading edge section that is between 85% and 92.5% of the wingspan measured from the root 2.2.

[0052] Figures 3A to 3E Several embodiments of the present invention are shown, in which the protrusion 3 is located at different positions along the wingspan of the vertical tail surface 1.2. The protrusion 3 of these embodiments includes a first lateral side 3.1 and a second lateral side 3.2. The first lateral side 3.1 is longer than the second lateral side 3.2 and the first lateral side 3.1 is closer to the tip 2.1 than the second lateral side 3.2. Each of the first lateral side 3.1 and the second lateral side 3.2 originates from different points on the leading edge 2 along the wingspan of the vertical tail, where these points do not coincide with the tip 2.1 and do not coincide with the root 2.2 either. Both the first lateral side 3.1 and the second lateral side 3.2 converge at the tip 3.1 of the protrusion. In this embodiment, the protrusion 3 includes a serrated shape.

[0053] InFigure 3A In [description], the intersection point of the second lateral side 3.2 of the protrusion 3 and the leading edge 2 is at 91.7% of the vertical fin span from the root 2.2. In Figure 3B In [description], the intersection point of the second lateral side 3.2 of the protrusion 3 and the leading edge 2 is at 82.3% of the vertical fin span from the root 2.2. In Figure 3C In [description], the intersection point of the second lateral side 3.2 of the protrusion 3 and the leading edge 2 is at 75% of the vertical fin span from the root 2.2. In Figure 3D In [description], the intersection point of the second lateral side 3.2 of the protrusion 3 and the leading edge 2 is at 66.6% of the vertical fin span from the root 2.2. In Figure 3E In [description], the intersection point of the second lateral side 3.2 of the protrusion 3 and the leading edge 2 is at 58.4% of the vertical fin span from the root 2.2. In Figures 3A to 3E In any embodiment of the [embodiment], the distance that the protrusion 3 protrudes from the leading edge 2 is included between 4% and 12% of the mean aerodynamic chord of the vertical fin surface 1.2. Additionally, also for these embodiments, the protrusion 3 extends along the vertical fin span between 4% and 12% of the vertical fin span.

[0054] At rudder angles of 0°, 10°, 20°, and 30°, for Figures 3A to 3E each embodiment of the [embodiment] (representing different positions of the protrusion along the leading edge in the vertical fin surface), the relationship between the side force coefficient "Cs" and the sideslip angle "β" has been compared with a baseline (representing a vertical fin surface without a protrusion according to the prior art). Additionally, at rudder angles of 0°, 10°, 20°, and 30°, for Figures 3A to 3E each embodiment of the [embodiment] (representing different positions of the protrusion along the leading edge in the vertical fin surface), the relationship between the drag coefficient "Cd" and the sideslip angle "β" has been compared with a baseline (representing a vertical fin surface without a protrusion). The rudder angle is the angle of the rudder relative to the vertical fin surface. The sideslip angle is the angle of attack of the vertical fin surface, that is, the angle between the aerodynamic profile of the vertical fin surface and the airflow impinging on the vertical fin surface. The term sideslip angle is used for the vertical fin surface, and the term angle of attack is used for the horizontal fin surface or the wing.

[0055] Considering a rudder angle of 0°, Figure 4A shows a graph of Cs versus β for Figures 3A to 3E each embodiment of the [embodiment] (respectively denoted as S1 to S5) compared with a baseline (denoted as BS). Additionally, Figure 4B shows a graph of Cd versus β for Figures 3A to 3E each embodiment of the [embodiment] (respectively S1 to S5) compared with a baseline (BS). Considering a rudder angle of 10°, Figure 5A shows forFigures 3A to 3E Graphs of Cs versus β comparing each of the embodiments (denoted as S1 to S5 respectively) with a baseline (denoted as BS). Additionally, Figure 5B shows Figures 3A to 3E graphs of Cd versus β comparing each of the embodiments (S1 to S5 respectively) with a baseline (BS) for Figure 6A Considering a rudder angle of 20°, Figures 3A to 3E graphs of Cs versus β comparing each of the embodiments (denoted as S1 to S5 respectively) with a baseline (denoted as BS). Additionally, Figure 6B shows Figures 3A to 3E graphs of Cd versus β comparing each of the embodiments (S1 to S5 respectively) with a baseline (BS) for Figure 7A Considering a rudder angle of 30°, Figures 3A to 3E graphs of Cs versus β comparing each of the embodiments (denoted as S1 to S5 respectively) with a baseline (denoted as BS). Additionally, Figure 7B shows Figures 3A to 3E graphs of Cd versus β comparing each of the embodiments (S1 to S5 respectively) with a baseline (BS) for

[0056] From Figures 4A to 7B these data comparisons in Figures 3A to 3E it can be concluded that for each of the embodiments of Figures 3A to 3E by providing a protrusion 3 according to the configuration of the present invention (specifically according to the embodiment shown in Figures 3A to 3E ), the side force coefficient Cs generated on the vertical fin surface 1.2 increases compared to the baseline. Thus, compared to the baseline, the control of the vertical fin surface 1.2 at high sideslip angles β is improved, and the influence on the drag coefficient Cd is very limited / zero. Therefore, the negative impact on fuel consumption is very small or non - existent.

[0057] Figure 8 shows an aircraft 6 according to an embodiment of the present invention. The aircraft 6 includes a horizontal fin surface 1.1 and a vertical fin surface 1.2, and the vertical fin surface 1.2 includes a protrusion 3 according to an embodiment of the present invention.

[0058] The project generating this application has received funding from the CleanSky 2 Joint Undertaking (JU) under grant agreement No. 864290. The Joint Undertaking has received support from the European Union's Horizon 2020 research and innovation programme and from CleanSky 2 Joint Undertaking members outside the European Union.

Claims

1. An aircraft tail surface (1), comprising a leading edge (2), a trailing edge (5), a tip (2.1) and a root (2.2), wherein: The aircraft tail surface (1) further comprises a single protrusion (3) protruding from the leading edge (2), wherein the protrusion (3): protrudes from the leading edge (2) only in a direction opposite to the trailing edge (5), and the protrusion (3) is located closer to the tip (2.1) than to the root (2.2); and The tail wing comprises a first lateral side portion (3.1) and a second lateral side portion (3.2), wherein the first lateral side portion (3.1) and the second lateral side portion (3.2) originate from different points of the leading edge (2) along the span of the tail wing, and the points do not coincide with the tip (2.1) or the root (2.2); wherein the first lateral side portion (3.1) is closer to the tip (2.1) than the second lateral side portion (3.2); And wherein the protrusion (3) is located entirely in a section of the leading edge (2) comprised between 50% and 95% of the span of the tail wing from the root (2.2).

2. Aircraft tail surface (1) according to the preceding claim, wherein: The first lateral side (3.1) and the second lateral side (3.2) of the protrusion (3) converge at a protrusion tip (3.3).

3. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The first lateral side (3.1) and / or the second lateral side (3.2) of the protrusion (3) is curved.

4. Aircraft tail surface (1) according to the preceding claim, wherein: The first lateral side (3.1) and / or the second lateral side (3.2) comprises a convex shape.

5. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The protrusion (3) comprises a sinusoidal shape.

6. Aircraft tail surface (1) according to any one of the preceding claims, wherein: The protrusion (3) comprises a sawtooth shape.

7. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The projection is located entirely in a section of the leading edge (2) between 60% and 80% of the span of the empennage from the root (2.2).

8. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The distance at which the protrusion (3) protrudes from the leading edge (2) is comprised between 4% and 12% of the mean aerodynamic chord of the aircraft tail surface (1).

9. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The protrusion (3) extends along the empennage span between 4% and 12% of the empennage span, and preferably between 6% and 9% of the empennage span.

10. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The aircraft tail surface (1) is a horizontal tail surface (1.1).

11. An aircraft tail surface (1) according to any one of claims 1 to 9, wherein: The aircraft tail surface (1) is a vertical tail surface (1.2).

12. An aircraft tail surface (1) according to any one of claims 1 to 9, wherein: The aircraft tail surface (1) is a swept back surface or a forward swept surface.

13. An aircraft tail surface (1) according to any one of the preceding claims, wherein: The aspect ratio of the protrusion (3) is comprised between 0.8 and 1.

2.

14. Aircraft tail surface (1) according to the preceding claim, wherein: The length-to-width ratio of the protrusion (3) is 1.

15. An aircraft (6) comprising at least one aircraft tail surface (1) according to any one of the preceding claims.

Images