WO2012136978A1

WO2012136978A1 - An aircraft landing gear

Info

Publication number: WO2012136978A1
Application number: PCT/GB2012/050622
Authority: WO
Inventors: Stuart Lacy; Geoff CUMNER
Original assignee: Messier-Dowty Limited
Priority date: 2011-04-05
Filing date: 2012-03-22
Publication date: 2012-10-11
Also published as: GB201105766D0; GB2489715A

Abstract

An aircraft landing gear (10) comprising a noise-inducing component region (12) and an airflow disruption element (16) having a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, the noise-inducing component region such that, in use with the landing gear deployed, the airflow disruption element faces, and at least partially disrupts, an airflow(A) moving towards the noise-inducing component region, wherein the cross-sectional area of the airflow disruption element is less than the cross-sectional area of the noise-inducing component region.

Description

An Aircraft Landing Gear

Background

Aircraft can generate considerable noise during a landing approach. Some of this noise is caused by air flowing around the deployed landing gear. Although the aircraft may be travelling at around 80 metres per second, the localised air flow around a noise-inducing component of the landing gear may reach speeds of around 300 metres per second, thereby generating considerable noise. Such noise is particularly undesirable because of the fact that airports are often located close to cities or other densely populated areas.

In an attempt to address such noise problems, it is known to provide an aircraft landing gear with fairings. Fairings are basically covers, usually made from metal or composite materials, arranged to shield a noise-inducing component of the landing gear from air flow during landing.

However, the present inventors have identified that fairings can considerably increase the total envelope of the landing gear and/or affect articulation of the landing gear for stowage and/or affect the kinematics of the landing gear during landing and ground operation including inspection because they are each designed to shield a noise-inducing component. Also, fairings may increase the total weight of the landing gear by an undesirable amount.

Summary

In accordance with a first aspect of the present invention, there is provided an aircraft landing gear comprising a noise-inducing component region and an airflow disruption element having a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, the noise-inducing component region such that, in use with the landing gear deployed, the airflow disruption element faces, and at least partially disrupts, an airflow moving towards the noise-inducing component region, wherein the cross-sectional area of the airflow disruption element is less than the cross- sectional area of the noise-inducing component region. Thus, the relatively small airflow disruption element is provided upstream from the noise- inducing component region and is spaced from it. As such, the airflow disruption element generates downstream turbulence that may reduce the noise generated by the noise- inducing component region relative to the noise that would otherwise be generated by a generally laminar airflow negotiating the noise-inducing component region. The airflow disruption element is thus arranged to reduce the noise created by the noise-inducing component region. This advantage may be provided for relatively little additional weight and size because of the fact that the airflow disruption element is spaced from, and thus can be smaller than, rather than being designed to shield, the noise-inducing component region.

The airflow disruption element may have a second configuration in which it is located closer to the landing gear than in the first configuration, the landing gear including an actuator arranged to move the airflow disruption element between the first and second configurations. The actuator may be arranged to move the airflow disruption element between the first and second configurations in a pivotal or linear manner.

Thus, in such a case, the airflow disruption element may be movable to a second configuration that is more suitable for stowing the landing gear. This means that in the first configuration the airflow disruption element may be spaced at an optimum disruption, or noise-reducing, distance from the noise-inducing component region irrespective of whether such a spacing is suitable for stowing the landing gear.

The airflow disruption element may be mounted on an elongate arm that is coupled to the landing gear. The mounting arm may be a tube or the like.

Thus, in such a case, the airflow disruption element may be mounted on thin, elongate arm such as a low-weight tube made from composite material. The airflow disruption element may be operable to increase or decrease its cross-sectional area in response to a control signal. The airflow disruption element may include one or more vanes pivo tally movable so as to increase or decrease the cross-sectional area of the airflow disruption element. Thus, in such a case, the cross-sectional area of the airflow disruption element may be enlarged for use and decreased for stowing. Enlargement of the cross-sectional area of the airflow disruption element may increase the downstream turbulence generated by the airflow disruption element.

The airflow disruption element may be arranged to vibrate and/or rotate.

Thus, in such a case, the downstream turbulence generated by the airflow disruption element may be increased relative to a non- vibrating and/or non-rotating airflow disruption element.

The airflow disruption element may be arranged to articulate in a generally lateral plane and/or in a generally vertical plane.

Thus, in such a case, the articulation of the airflow disruption element may improve airflow disruption over the noise-inducing component in a crosswind approach and/or improve airflow disruption over the noise-inducing component for varying vertical descent velocity of the aircraft, respectively.

The airflow disruption element may, when in the first configuration, be spaced from the noise-inducing component region by a distance determined in a wind tunnel test, or computer fluid dynamic analysis, for specific configurations of airflow disruption element and noise-inducing component. In some embodiments the spacing may be at least 3mm, at least 5mm, at least 10mm, at least 15mm, at least 20mm, at least 25mm, at least 30mm, at least 40mm, at least 50mm, at least 60mm, at least 70mm, at least 80mm, at least 90mm, at least 100mm, at least 110mm, at least 120mm, at least 130mm, at least 140mm, or at least 150mm. The cross sectional area of the airflow disruption element may smaller than the cross sectional area of the noise-inducing component region that the airflow disruption element is arranged to affect by an amount determined in a wind tunnel test, or computer fluid dynamic analysis, for specific configurations of airflow disruption element and noise- inducing component. In some embodiments the airflow disruption element may be at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 400% or 500% smaller than the cross sectional area of the noise-inducing component region 12 that the airflow disruption element is arranged to affect.

The noise-inducing component region may comprise a component of the aircraft landing gear such as a main fitting, strut, stay, spar, lock link, axle, bogie, torque link, pin assembly, actuator, valve, manifold, dressing, brake component or the like.

The aircraft landing gear may comprise a plurality of noise-inducing regions and a plurality of airflow disruption elements, each airflow disruption element having a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, a respective one of the noise-inducing component regions such that, in use with the landing gear deployed, the airflow disruption element faces, and at least partially disrupts, an airflow moving towards the noise-inducing component region, wherein the cross-sectional area of the airflow disruption element is less than the cross-sectional area of the noise- inducing component region. A plurality of the airflow disruption element may include one or more of the optional features described above with reference to the first aspect.

In accordance with a second aspect of the present invention, there is provided an airflow disruption element specially adapted for use with an aircraft landing gear according to the first aspect. In accordance with a third aspect of the present invention, there is provided an aircraft including an aircraft landing gear according to the first aspect.

Brief Description of the Drawings By way of example only, certain embodiments of the invention will now be described by reference to the accompanying drawings, in which; Figure 1 is a schematic, side view of an aircraft landing gear according to a first embodiment of the present invention;

Figure 2 is a schematic, side view of the aircraft landing gear of Figure 1, showing the airflow disruption element in a retracted configuration;

Figure 3 is a schematic, side view of an aircraft landing gear according to a second embodiment of the present invention;

Figure 4 is a schematic, side view of an aircraft landing gear according to a third embodiment of the present invention, showing the airflow disruption element with an enlarged cross sectional area;

Figure 5 is a schematic, side view of the aircraft landing gear of Figure 4, showing the airflow disruption element with an reduced cross sectional area; and

Figure 6 is a schematic, side view of an aircraft landing gear according to a fourth embodiment of the present invention, including a plurality of airflow disruption elements. Detailed Description

Figures 1 and 2 show a schematic side view of a landing gear 10 according to a first embodiment of the present invention. The landing gear 10 is shown in a deployed configuration, suitable for takeoff and landing. Due to the motion of the aircraft to which it is coupled, the landing gear moves generally in the direction of arrow M, which will be referred to as the landing gear motion direction M. Consequently, airflow moves relative to the landing gear 10 generally in the direction of arrow A, which will be referred to as airflow A. Airflow A can be considered to be a primary or resultant airflow from both the aircrafts forward and vertical velocity and will usually also include a crosswind component.

The landing gear 10 comprises a noise-inducing component region 12 that, due to its configuration, would generate noise as airflow A negotiates it i.e. moves around and beyond the noise-inducing component region 12.

The landing gear 10 further comprises and an airflow disruption element 16. The airflow disruption element 16 has a first configuration in which it is spaced from the noise- inducing component 12. The airflow disruption element 16 is arranged in an upstream relationship with respect to noise-inducing component region 12. Thus, in use with the landing gear 10 deployed, the airflow disruption element 16 faces, and at least partially disrupts, the airflow A moving towards the noise-inducing component region 12. The cross-sectional area of the airflow disruption element 16 is less than the cross-sectional area of the noise-inducing component region 12.

The term "cross sectional area" when used in conjunction with the airflow disruption element 16 means the area of a cross section through the airflow disruption element 16 that is generally orthogonal with respect to the landing gear motion direction M. As will be appreciated, the landing gear motion direction M will be generally parallel with respect to the longitudinal axis of the aircraft (not shown). In some embodiments of the invention, the cross sectional area may be the largest cross sectional area of the airflow disruption element 16 that is generally orthogonal to the landing gear motion direction M, which in the illustrated embodiment would be the rear or downstream face of the airflow disruption element 16, or the mean cross sectional area.

The term "cross sectional area" when used in conjunction with the noise-inducing component region 12 means a cross section through the noise-inducing component region 12 that is generally orthogonal to the landing gear motion direction M. In some embodiments of the invention, the cross sectional area may be the largest cross sectional area of the noise-inducing component or component region 12 that is generally orthogonal to the landing gear motion direction M, or the mean cross sectional area. Thus, in terms of the airflow A, the relatively small airflow disruption element 16 is provided upstream from the noise-inducing component region 12 and is spaced from it. As such, the airflow disruption element 16 generates downstream turbulence that may reduce the noise generated by the noise-inducing component region 12 relative to the noise that would otherwise be generated by generally laminar airflow negotiating the noise-inducing component region 12. This advantage may be provided for relatively little additional weight and size because of the fact that the airflow disruption element 16 is spaced upstream from, and thus may be smaller than, rather than being designed to shield, the noise-inducing component region 12. In the illustrated embodiment, the airflow disruption element 16 is mounted on an elongate arm 18, the other end of which is coupled to a part of the landing gear, such as a strut. The mounting arm 18 may be a tube or the like formed from any suitable material, such as aluminium or composites. It should however be noted that the airflow disruption element 16 may be mounted in any suitable manner.

In the illustrated embodiment, the arm 18 is longitudinally extendable and thus may increase and decrease in length. The arm 18 may comprise a rod and piston actuator. When the arm 18 is relatively long, the airflow disruption element 16 is in the first configuration in which it is spaced from the noise-inducing component 12. When the arm 18 is relatively short, the airflow disruption element 16 is in a second configuration in which it is located closer to the centre of the landing gear 10 than in the first configuration. The arm 18 is thus arranged to move the airflow disruption element 16 between the first and second configurations in a linear manner, with a displacement E. The arm 18 may be controlled in any conventional manner, such as by a control system arranged to automatically deploy the disruption element 16 to the first configuration once the landing gear 10 is fully deployed, and to automatically retract the disruption element 16 as the landing gear 10 begins to move towards a stowed configuration. Thus, in such embodiments, the airflow disruption element 16 may be movable to a second configuration that is more suitable for stowing the landing gear. This means that in the first configuration the airflow disruption element 16 may be spaced at an optimum disruption or noise-reducing distance from the noise-inducing component region 12 without consideration as to whether such spacing is suitable for stowing.

As noted above, in use, with the landing gear 10 deployed, the airflow disruption element 16 faces, and at least partially disrupts, the airflow A moving towards the noise-inducing component region 12. Consequently, the airflow A is manipulated by the airflow disruption element 16 i.e. the airflow disruption element 16 pushes at least some of the airflow out of the way of the noise-inducing component region 12, as schematically illustrated by airflow disruption line T. This creates turbulent airflow downstream of he airflow disruption element 16, the turbulent airflow generally causing less noise as it negotiates the noise-inducing component region 12 than would be the case for an undisrupted airflow. Thus, in some embodiments, the airflow disruption element 16 can be considered to act as an aero acoustic spike.

Referring to Figure 3, a schematic side view of a landing gear 20 according to a second embodiment of the present invention is shown. The landing gear 20 is similar to landing gear 10 of the first embodiment except that the arm 18 is a rigid linkage pivotally movable by an actuator 24. The arm 20 is thus arranged to move the airflow disruption element 16 between the first and second configurations in an arc. Referring to Figures 4 and 5, a schematic side view of a landing gear 30 according to a third embodiment of the present invention is shown. The landing gear 30 is similar to landing gear 10 of the first embodiment except that, in the third embodiment, the airflow disruption element 16 is operable to increase and decrease its cross-sectional area in response to a control signal. Many suitable control systems will be apparent to a skilled person for generating the control signal. The increase and decrease in cross-sectional area may be achieved by any suitable means, such as the airflow disruption element 16 including one or more vanes 32 pivotally movable so as to increase or decrease the cross- sectional area of the airflow disruption element 16. As shown in Figure 4, with the vanes 32 deployed the cross sectional area through a part of the airflow disruption element 16 in the region of the vanes 32 is larger than the cross sectional area of the airflow disruption element 16 when the vanes are retracted, as shown in Figure 5. Thus, in the illustrated embodiment the cross-sectional area of the airflow disruption element 16 may be enlarged for use and decrease for stowing. Referring to Figure 6, a schematic side view of a landing gear 40 according to a fourth embodiment of the present invention is shown. The landing gear 40 comprises a plurality of noise-inducing regions and a plurality of airflow disruption elements 42. Each airflow disruption element 42 has a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, a respective one of the noise-inducing component regions 12 such that, in use with the landing gear deployed, the respective airflow disruption element 42 faces, and at least partially disrupts, an airflow A moving towards the respective noise-inducing component region 12. The airflow disruption elements 42 each have a maximum cross sectional area that is smaller than the maximum cross sectional area of the airflow disruption element 16 described above and consequently are mounted closer to the noise-inducing component regions 12. Due to this, the airflow disruption elements 42 may be permanently maintained in the first configuration, such as by being rigidly mounted.

A plurality of the airflow disruption elements 42 of the landing gear 40 according to the fourth embodiment of the present invention may include one or more of the features described above with reference to the first, second or third embodiments of the invention. In any of the embodiments of the invention, the airflow disruption element may, when in the first configuration, be spaced from the noise-inducing component region by a distance determined in a wind tunnel test, or computer fluid dynamic analysis, for specific configurations of airflow disruption element and noise-inducing component. In some embodiments the spacing may be at least 3mm, at least 5mm, at least 10mm, at least 15mm, at least 20mm, at least 25mm, at least 30mm, at least 40mm, at least 50mm, at least 60mm, at least 70mm, at least 80mm, at least 90mm, at least 100mm, at least 110mm, at least 120mm, at least 130mm, at least 140mm, or at least 150mm.

In any of the embodiments of the invention, the cross sectional area of the airflow disruption element may be smaller than the cross sectional area of the noise-inducing component region that the airflow disruption element is arranged to affect by an amount determined in a wind tunnel test, or computer fluid dynamic analysis, for specific configurations of airflow disruption element and noise-inducing component. In some embodiments the airflow disruption element may be at least 5%, 10%, 15%, 20%>, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 400% or 500% smaller than the cross sectional area of the noise-inducing component region 12 that the airflow disruption element is arranged to affect i.e. reduce the noise. In any of the embodiments of the invention, the noise-inducing component region 12 may comprise a component of the aircraft landing gear such as a main fitting, strut, stay, spar, lock link, axle, bogie, torque link, pin assembly, valve, actuator, manifold, dressing, brake component or the like. In any of the embodiments of the invention, the airflow disruption element(s) 16, 42 may be arranged to vibrate, expand and/or rotate. Thus, in such a case, the downstream turbulence generated by the airflow disruption element(s) 16, 42 may be increased relative to a non-vibrating airflow disruption element. Many suitable vibrations means will be apparent to a skilled person, such as providing a resiliently flexible property to at least some of the arm 18, 22 or providing an eccentric, rotatably actuated mass in the airflow disruption element(s) 16, 42, and any suitable means may be provided to cause the airflow disruption element(s) 16, 42 to vibrate.

In any of the embodiments of the invention, the airflow disruption element(s) 16, 42 may be arranged to articulate in a lateral plane and/or in a vertical plane. Many suitable mechanisms and control systems for achieving this will be apparent to a skilled person, such as through pivotal movement of the arm 20. The articulation of the airflow disruption element(s) 16, 42 may improve airflow disruption over the noise-inducing component region(s) 12 in a crosswind approach and/or improve airflow disruption over the noise- inducing component region(s) 12 for varying vertical descent velocity of the aircraft, respectively. In any of the embodiments of the invention, the landing gear according to embodiments of the invention may be a main landing gear assembly.

In any of the embodiments of the invention, the airflow disruption element(s) 16, 42 may be a provided exclusively for the purpose of at least partially disrupting the airflow A moving towards the noise-inducing component region 12.

In any of the embodiments of the invention, the airflow disruption element(s) 16, 42 may be implemented at the micro scale, mounted on multiple hair-like spikes, rather than the macro scale as described in at least some of the embodiments above.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parenthesis shall not be construed as limiting the claims. The word "comprising" can mean "including" or "consisting of and therefore does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice- versa. Parts of the invention may be implemented by means of hardware comprising several distinct elements, and/or by means of a suitably programmed computer. In a device claim enumerating several parts, several of these parts may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An aircraft landing gear comprising a noise-inducing component region and an airflow disruption element having a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, the noise-inducing component region such that, in use with the landing gear deployed, the airflow disruption element faces, and at least partially disrupts, an airflow moving towards the noise-inducing component region, wherein the cross-sectional area of the airflow disruption element is less than the cross- sectional area of the noise-inducing component region.

2. An aircraft landing gear according to claim 1, wherein the airflow disruption element has a second configuration in which it is located closer to the landing gear than in the first configuration, the landing gear including an actuator arranged to move the airflow disruption element between the first and second configurations.

3. An aircraft landing gear according to claim 2, wherein the actuator is arranged to move the airflow disruption element between the first and second configurations in a pivotal or linear manner.

4. An aircraft landing gear according to any preceding claim, wherein the airflow disruption element is mounted on an elongate arm that is coupled to the landing gear.

5. An aircraft landing gear according to any preceding claim, wherein the airflow disruption element is arranged so as to be operable to increase or decrease its cross- sectional area in response to a control signal.

6. An aircraft landing gear according to claim 5, wherein the airflow disruption element includes one or more vanes pivotally movable so as to increase or decrease the cross-sectional area of the airflow disruption element.

7. An aircraft landing gear according to any preceding claim, wherein the airflow disruption element is arranged to vibrate and/or rotate.

8. An aircraft landing gear according to any preceding claim, wherein the airflow disruption element is, when in the first configuration, spaced from the noise-inducing component region by one or more of the following: at least 3mm, at least 5mm, at least 10mm, at least 15mm, at least 20mm, at least 25mm, at least 30mm, at least 40mm, at least 50mm, at least 60mm, at least 70mm, at least 80mm, at least 90mm, at least 100mm, at least 110mm, at least 120mm, at least 130mm, at least 140mm, at least 150mm.

9. An aircraft landing gear according to any preceding claim, wherein cross sectional area of the airflow disruption element is at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 400% or 500% smaller than the cross sectional area of the noise-inducing component region 12 that the airflow disruption element is arranged to affect.

10. An aircraft landing gear according to any preceding claim, wherein the noise- inducing component region comprises a component of the aircraft landing gear such as a main fitting, strut, stay, spar, lock link, axle, bogie, torque link, pin assembly, actuator, valve, manifold, dressing, brake component or the like.

11. An aircraft landing gear according to any preceding claim comprising a plurality of noise-inducing regions and a plurality of airflow disruption elements, each airflow disruption element having a first configuration in which it is spaced from, and arranged in an upstream relationship with respect to, a respective one of the noise-inducing component regions such that, in use with the landing gear deployed, the airflow disruption element faces, and at least partially disrupts, an airflow moving towards the noise-inducing component region, wherein the cross-sectional area of the airflow disruption element is less than the cross-sectional area of the noise-inducing component region.

12. An aircraft landing gear according to any preceding claim, wherein the airflow disruption element is arranged to articulate in a generally lateral plane and/or in a generally vertical plane.

13. An aircraft landing gear substantially as herein described with reference to the accompanying drawings.

14. An airflow disruption element specially adapted for use with an aircraft landing gear according to any of claims 1 to 13.

15. An aircraft including an aircraft landing gear according to any of claims 1 to 13.