Wing tip device having configurations for flight and ground-based operations

Abstract

An aircraft including a wing, the end of the wing having a wing tip device, wherein the wing tip device includes a moveable region that is rotatable, about an axis of rotation extending out of the plane of the wing tip device, between: (i) a high-altitude cruise configuration in which the moveable region extends downwardly below the wing; and (ii) a ground-operating configuration in which the moveable region extends rearwardly behind the wing such that the ground clearance of the wing tip device is increased.

Claims

1. A wing for an aircraft, the wing including an end and comprising: a wing tip device at the end, wherein the wing tip device is configurable between: (i) a high-altitude cruise configuration in which the wing tip device extends downwardly below the wing; and (ii) a ground-operating configuration in which the wing tip device extends rearwardly such that the ground clearance of the wing tip device is increased and an effective span of the wing is decreased.

2. The wing according to claim 1, wherein the wing tip device comprises a moveable region that is rotatable about an axis of rotation extending out of a plane of the wing tip device, such that: in the high-altitude cruise configuration the moveable region extends downwardly below the wing; and in the ground-operating configuration the moveable region extends rearwardly behind the wing.

3. The wing according to claim 1, wherein the aircraft is suitable for high-altitude flight between 15,000 and 45,000 ft.

4. The wing according to claim 1, wherein the aircraft is suitable for flight at speeds of between Mach 0.5 and Mach 0.9.

5. The wing according to claim 1 wherein the wing is a dihedral wing.

6. The wing according to claim 1, wherein the end of the wing comprises a bulbous body protruding beyond an airfoil cross-section of the wing, the wing tip device extending from the bulbous body.

7. The wing according to claim 1, the end of the wing having a second wing tip device, and wherein second wing tip device extends upwardly above the wing.

8. An aircraft comprising at least one wing according to claim 1.

9. An aircraft comprising: a wing including an end; a wing tip device at the end of the wing, wherein the wing tip device comprises a moveable region that is rotatable, about an axis of rotation extending out of a plane of the wing tip device, between: (i) a high-altitude cruise configuration in which the moveable region extends downwardly below the wing; and (ii) a ground-operating configuration in which the moveable region extends rearwardly such that the ground clearance of the wing tip device is increased.

10. The aircraft according to claim 9 wherein the wing tip device comprises a fixed region which extends downwardly from the wing and is fixed relative thereto, and wherein the moveable region is rotatably mounted on the fixed region.

11. A method of configuring a wing tip device on a wing of an aircraft, the method comprising: during flight of the aircraft, configuring the wing tip device in a high-altitude cruise configuration, wherein the wing tip device downwardly extends below the wing; and during ground-based operations of the aircraft, configuring the wing tip device in a ground-operating configuration, wherein the wing tip device extends rearwardly behind the wing to increase the ground clearance of the wing tip device and to decrease an effective span of the wing and wing tip device.

Description

DESCRIPTION OF THE DRAWINGS

(1) Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings of which:

(2) FIG. 1 is a front view of an aircraft according to a first embodiment of the invention;

(3) FIG. 2 is a slightly-off end-on view of the wing and wing tip device on the aircraft of FIG. 1;

(4) FIG. 3 is a plan view of the wing and wing tip device on the aircraft of FIG. 1;

(5) FIG. 4 is a front view of the wing and wing tip device on the aircraft of FIG. 1;

(6) FIG. 5 is a perspective view of a wing and wing tip device on an aircraft according to a second embodiment of the invention;

(7) FIG. 6 is an end-on view of the wing and wing tip device of FIG. 5;

(8) FIG. 7 is a front view of the wing and wing tip device of FIG. 5;

(9) FIGS. 8 and 9 are front views of a wing and wing tip device according to further embodiments of the invention;

(10) FIG. 10 is a perspective view of a wing and wing tip device on an aircraft according to yet another embodiment of the invention;

(11) FIG. 11 is an end-on view of the wing and wing tip device of FIG. 10;

(12) FIGS. 12a and 12b are perspective views of a wing and wing tip device according to a further embodiment of the invention, the wing tip device being shown in the high-altitude cruise and the ground-operating configurations respectively; and

(13) FIG. 12c is a front view of the wing tip device in FIG. 12b.

DETAILED DESCRIPTION

(14) FIG. 1 is a front view of one side of an aircraft 1 having a dihedral wing 3 and a downwardly extending wing tip device 5. The aircraft 1 is a passenger aircraft designed for cruise flight between 35,000 and 42,000 ft at around Mach 0.80-0.85. The planar wing tip device 5 is shown in a high-altitude cruise configuration in which the device 5 extends at a cant of around 160 degrees (i.e. 70 degrees below the horizontal).

(15) The aerodynamic benefits of wing tip devices per se (typically in reducing induced drag) are well known. It can be desirable to have relatively long wing tip devices, but the length of downwardly extending wing tip devices tends to be limited by airport operating rules which govern various clearances required when maneuvering around the airport (such as the span and/or ground clearance required for gate entry).

(16) FIGS. 2, 3 and 4 show the wing tip device on the aircraft of the first embodiment of the invention from end, plan and front elevations respectively. For the sake of clarity, the effective span increase s, created by the wing tip device, is exaggerated in the plan view of FIG. 3.

(17) The wing tip device 5 is formed of a fixed region 7 adjoining the aircraft wing 3, and a moveable region 9. A thin extension element (not shown) on the moveable region 9 overlaps the underside of the fixed region 7. The moveable region 9 is rotatably mounted on the fixed region 7 about an axis of rotation 11 (see FIG. 4) that passes through the overlap.

(18) In FIG. 2, the structure defining the moveable region 9 is drawn as a continuous line to show the wing tip device 5 in a high-altitude cruise configuration, and is drawn as a dashed line to show the wing tip device 5 in a ground-operating configuration (described in more detail below). In FIG. 4, the rotatable region 9 is drawn as a dashed line to show the wing tip device 5 in the high-altitude cruise configuration, and is not visible in the ground-operating configuration (because it is obscured by the structure of the fixed region 7).

(19) Referring to FIGS. 2 and 4, in the high-altitude cruise configuration, the moveable region 9 of the wing tip device 5 extends downwardly a distance D below the underside of the wing 3. Due to the cant of the wing tip device, it also increases the effective span of the wing 3 by a distance S. Such geometry is beneficial in reducing induced drag, but the downward and spanwise extensions D, S of the wing tip device are too great for airport clearance rules. To mitigate this, the wing tip device is configurable to the ground-operating configuration in which the moveable region 9 of the wing tip device 5 extends rearwardly behind the wing 3 substantially in line with the streamwise direction. The axis of rotation 11 of the moveable region 9 extends perpendicularly out of the plane of the wing tip device 5 such that the moveable region 9 rotates in its own plane. This reduces the downward extension of the wing tip device to a distance d and also reduces the contribution to the effective span to a reduced distance s, such that the aircraft (when the wing tip device 5 is in the ground-operating configuration) complies with airport clearance rules. The aircraft of the present invention can therefore benefit from the aerodynamic improvements of the wing tip device during flight, especially high-altitude cruise flight, whilst still being able to manoeuvre on the ground.

(20) In the first embodiment of the invention, the wing tip device is substantially planar (no curve or camber) and of aerofoil cross-section. The fixed region 7 is set back a short distance from the leading edge of the wing 3 (see FIG. 3), but has the same sweep angle alpha. When the wing tip device 5 is arranged in the high-altitude cruise configuration, the moveable region 9 has the same sweep as the fixed region 7 and there is a smooth aerodynamic between the two; however when the tip device 5 is configured in the ground-operating configuration the sweep is increased (by rotating the moveable region 9 about the axis 11) such that the moveable region 9 is substantially streamwise.

(21) The moveable region 9 is actuated by a motor (not shown) installed within the structure defining the fixed region 7. The motor drives a series of bevel gears to effect rotation. In other embodiments of the invention, different actuation mechanisms may be used, such as hydraulics or a morphing wing structure.

(22) In the first embodiment of the invention, the aircraft comprises a control system (not shown) for control operation of the wing tip device between the two configurations. Prior to, and during, take-off, the wing tip device is in the ground-operating configuration. Shortly after take-off, the control system instructs the motor to rotate the moveable region 9 of the wing tip device 5 downwards and forward such that it matches the sweep of the fixed region 7 and is downwardly extending. The wing tip device maintains this high-altitude cruise configuration during climb, cruise and descent. As the aircraft approaches landing, the control system instructs the motor to reverse the rotation of the moveable region 9 such that the wing tip device reverts to the ground operating configuration.

(23) A second embodiment of the invention is shown in FIGS. 5 to 7. Features in the second embodiment of the invention that correspond to similar features in the first embodiment of the invention, are shown with the same reference numerals as in the first embodiment, but with the addition of the prefix 1 (or 10 where appropriate). The second embodiment is identical to the first embodiment except that the aircraft also comprises an upwardly extending wing tip device 113 at the end of the wing 103. The upwardly extending wing tip device 113 is fixed at a cant of 20 degrees (see FIG. 7) and is arranged to reduce downwash and improve sidewash. By using the upwardly extending device 113 in conjunction with the downwardly extending wing tip device 105, the net vorticity is reduced (in comparison to the upwardly extending device alone). The upwardly extending device is positioned forward of the downwardly extending device (see FIG. 6). In the second embodiment of the invention, the wing tip also comprises a bulbous body 115 from which the wing tip devices extend. The bulbous body 115 houses the actuator (not shown) for moving the downwardly extending wing tip device 105.

(24) FIGS. 8 and 9 are front views of wing tip devices according to other embodiments of the invention. In the embodiment of FIG. 8, the reference numbers are 200 series numbers and each correspond to a respective one of the 100 series numbers shown in FIGS. 5 to 7. For example, the end of a wing is designated by reference number 203 in FIG. 8 and designated by 103 in FIG. 5. In FIG. 8, the upwardly extending wing tip device 213 is fixed at a lower cant than the second embodiment of the invention, and the bulbous body 215 protrudes further on the lower side of the wing 203 than the upper side. In the embodiment of FIG. 9, the reference numbers are 300 series numbers and each correspond to the 100 series numbers shown in FIGS. 5 to 7. For example, the end of a wing is designated by reference number 303 in FIG. 9 and designated by 103 in FIG. 5. The bulbous region 315 is located adjacent the root of the fixed region 307 of the downwardly extending device 305, but does not extend all the way to the leading edge of the wing.

(25) Yet another embodiment of the invention is shown in FIGS. 10 and 11, the reference numbers are 400 series numbers and each correspond to a respective one of the 100 series numbers shown in FIGS. 5 to 7. For example, the end of a wing is designated by reference number 403 in FIG. 10 and designated by 103 in FIG. 5. This embodiment of the invention is identical to the second embodiment except that the wing tip does not include a bulbous body at the root of the upwardly and downwardly extending devices 413 and 405.

(26) In the above-mentioned embodiments, the moveable region is rotatably mounted on the underside of the structure defining the fixed region, and the axis of rotation of the moveable region 9, 109, 209, 309 and 409-extends perpendicularly out of the plane of the wing tip device 5, 105, 205, 305 and 405 such that the moveable region rotates in its own plane. FIGS. 12a to 12c show a further embodiment of the invention. The reference numbers in FIGS. 12a to 12c are 500 series numbers and each correspond to a respective one of the 100 series numbers shown in FIGS. 5 to 7. For example, the upwardly extending device is designated by reference number 513 in FIG. 12a and designated by 113 in FIG. 5. In FIGS. 12a to 12c, the moveable region 509 instead rotates about an axis 517 that is inclined to the plane of the wing tip device (the axis 517 thus extending at an angle out of the page in FIGS. 12a to 12c). In this embodiment, the fixed and moveable regions 507,509 do not overlap; instead the regions are divided along a cut-plane 519 passing through the wing tip device 505 (a notional elliptical boundary of the plane is shown in FIGS. 12a and 12c to indicate the cut-plane). The cut-plane 519 is orientated perpendicular to the axis of rotation 517. This ensures that when the moveable region 509 rotates from the high-altitude lift configuration (see FIG. 12a) to the ground-operating configuration (see FIGS. 12b and 12c), it does not interfere with the fixed region 507. Orientating the cut-plane 517 in this manner removes the need for cut-aways in one or both regions of the wing tip device 505, and/or the need for more complex rotational movements.

(27) Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.