Wing tip device

Abstract

A wing tip device for fixing to the outboard end of a wing, the wing defining a wing plane, the wing tip device comprising: an upper wing-like element projecting upwardly with respect to the wing plane and having a trailing edge; and a lower wing-like element fixed with respect to the upper wing-like element and having a root chord and a trailing edge, the lower wing-like element root chord intersecting With the upper wing-like element, and the lower wing-like element projecting downwardly from the intersection.

What is claimed:  
     
         1 . A wing tip device for fixing to the outboard end of a wing, the wing defining a wing plane, the wing tip device comprising:
 an upper wing-like element projecting upwardly with respect to the wing plane and having a trailing edge; and   a lower wing-like element fixed with respect to the upper wing-like element and having a root chord and a trailing edge, the lower wing-like element root chord intersecting with the upper wing-like element, and the lower wing-like element projecting downwardly from the intersection,   wherein the upper wing-like element is larger than the lower wing-like element and the trailing edge of the lower wing-like element is adjacent the trailing edge of the upper wing-like element at the intersection, and   wherein an included angle between the upper and lower wing-like elements at the intersection is less than, or equal to, 160 degrees.   
     
     
         2 . A wing tip device according to  claim 1 , wherein the upper wing-like element includes a substantially planar portion and a non-planar curved wing tip extension adapted to smoothly blend the outboard end of the wing into the substantially planar portion of the upper wing-like element. 
     
     
         3 . A wing tip device according to  claim 2 , wherein the non-planar curved wing tip extension has increasing curvature of local dihedral in the outboard direction. 
     
     
         4 . A wing tip device according to  claim 1 , wherein the non-planar curved wing tip extension has continuously increasing sweepback of both the leading and trailing edges, and wherein the non-planar curved wing tip extension has continuously decreasing chord in the outboard direction. 
     
     
         5 . A wing tip device according to  claim 1 , wherein the root chord of the lower wing-like element extends along only part of the local chord of the Upper wing-like element at the intersection. 
     
     
         6 . A wing tip device according to  claim 5 , wherein a leading edge at the root of the lower wing-like element is positioned aft of a leading edge of the upper wing-like element. 
     
     
         7 . A wing tip device according to  claim 1 , wherein an included angle between the wing plane and the lower wing-like element is at least 110 degrees. 
     
     
         8 . A wing tip device according to  claim 1 , wherein the included angle between the upper and lower wing-like elements at the intersection is at least 80 degrees. 
     
     
         9 . A wing tip device according to  claim 1 , wherein the lower wing-like element is substantially planar. 
     
     
         10 . A wing tip device according to  claim 1 , wherein the lower wing-like element has a sweep back angle. 
     
     
         11 . A wing tip device according to  claim 1 , wherein the lower wing-like element root chord intersects with the transition portion of the upper wing-like element, such that the intersection between the lower wing-like element and the upper wing-like element is outboard of the outboard end of the wing. 
     
     
         12 . A wing having an outboard end and a wing tip device in accordance with  claim 1  fixed to its outboard end. 
     
     
         13 . An aircraft having a wing according to  claim 12 . 
     
     
         14 . An aircraft according to  claim 13 , wherein, when the aircraft is on the ground and the wing is subjected to downward deflection due to full fuel load, the tip of the lower wing-like element extends no further outboard in the spanwise direction than the tip of the upper wing-like element. 
     
     
         15 . An aircraft according to  claim 14 , wherein, when the aircraft is on the, ground and the wing is subjected to downward deflection due to full fuel load, the spanwise extent of the tip of the lower wing-like element is substantially equal to the spanwise extent of the tip of the upper wing-like element. 
     
     
         16 . An aircraft according to  claim 14 , wherein the spanwise extent of the wing in the ground shape is substantially equal to an airport compatibility gate limit. 
     
     
         17 . An aircraft according to any of  claims 14 , wherein, when the aircraft is in flight, the tip of the lower wing-like element extends further outboard in the spanwise direction than the tip of the upper wing-like element due to aeroelastic deformation of the wing shape. 
     
     
         18 . A method of fitting, or retro-fitting, a wing tip device to a wing, the method comprising fixing a wing tip device in accordance with  claim 1  to the outboard end of a wing. 
     
     
         19 . A method of modifying a wing tip device fixed to, or for fixing to, the outboard end of a wing, the wing defining a wing plane, the existing wing tip device comprising an upper wing-like element projecting upwardly with respect to the wing plane and having a trailing edge, and the method comprising providing a lower wing-like element smaller than the upper wing-like element and having a root chord and a trailing edge, and fixing the lower wing-like element to the upper wing-like element such that: the lower wing-like element root chord intersects with the upper wing-like element, and the lower wing-like element projects downwardly from the intersection; and that the trailing edge of the lower wing-like element is adjacent the trailing edge of the upper wing-like element at the intersection; and that an included angle between the upper and lower wing-like elements at the intersection is less than, or equal to, 160 degrees. 
     
     
         20 . A method of operating a wing having a wing tip device fixed to the outboard end of the wing, the wing defining a wing plane, and the wing tip device comprising:
 an upper wing-like element projecting upwardly with respect to the wing plane and having a trailing edge; and   a lower wing-like element fixed with respect to the upper wing-like element and having a root chord and a trailing edge, the lower wing-like element root chord intersecting with the upper wing-like element, and the lower wing-like element projecting downwardly from the intersection,   wherein the upper wing-like element is larger than the lower wing-like element and the trailing edge of the lower wing-like element is adjacent the trailing edge of the upper wing-like element at the intersection, and   wherein an included angle between the upper and lower wing-like elements at the intersection is less than, or equal to, 160 degrees, and   the method comprising subjecting the wing to aerodynamic loads such that the wing shape undergoes aeroelastic deformation to a state in which wing bending causes rotation of the wing tip device about the wing root such that the tip of the lower wing-like element extends further outboard in the spanwise direction than the tip of the upper wing-like element.   
     
     
         21 . A wing tip device for fixing to an outboard end of a wing, the wing defining a wing plane, the wing tip device comprising:
 an upper wing-like element projecting upwardly with respect to the wing plane including:
 a root end for fixing to the outboard end of the wing and having a root chord approximately equal to an outboard end chord of the wing, 
 a leading edge, 
 a trailing edge, 
 a substantially planar portion, and 
 a curved transition portion beginning at the root end and arranged to smoothly blend the outboard end of the wing into the substantially planar portion; and 
   a lower wing-like element smaller than the upper wing-like element and projecting downwardly with respect to the wing plane including:
 a root end fixed to a lower surface of the curved transition portion at an intersection outboard of the root end of the upper wing-like element, 
 a leading edge positioned aft of the leading edge of the upper wing-like element, and 
 a trailing edge substantially adjacent the trailing edge of the upper wing-like element. 
   
     
     
         22 . The wing tip device according to  claim 21 , wherein the leading edge of the upper wing-like element is swept backwards. 
     
     
         23 . The wing tip device according to  claim 21 , wherein the leading edge of the lower wing-like element is swept backwards. 
     
     
         24 . The wing tip device according to  claim 21 , wherein the lower wing-like element forms an angle with a tangent of the lower surface of the curved transition portion such that the lower wing-like element projects downwardly from the intersection and extends in an outboard direction. 
     
     
         25 . The wing tip device according to  claim 24 , wherein the angle is greater than approximately 80 degrees. 
     
     
         26 . The wing tip device according to  claim 21 , wherein the upper wing-like element, has continuously decreasing chord from the root end of the upper wing-like element to a tip chord of the upper wing-like element. 
     
     
         27 . The wing tip device according to  claim 21  wherein the leading edge of the upper wing-like element has continuously increasing sweep back in the transition portion. 
     
     
         28 . The wing tip device according to  claim 21 , wherein the trailing edge of the upper wing-like element has continuously increasing sweep back in the transition portion. 
     
     
         29 . The wing tip device according to  claim 21 , wherein the transition portion has increasing curvature of local dihedral in an outboard direction. 
     
     
         30 . The wing tip device according to  claim 21 , wherein an included angle between the upper and lower wing-like elements at the intersection is less than, or equal to, 160 degrees. 
     
     
         31 . A wing tip device for fixing to an outboard end of a wing, the wing defining a wing plane, the wing tip device comprising:
 an upper wing-like element projecting upwardly with respect to the wing plane including:
 a root end for fixing to the outboard end of the wing and having a root chord approximately equal to an outboard end chord of the wing, 
 a tip having a tip chord, 
 a trailing edge, 
 a substantially planar portion, and 
 a curved transition portion beginning at the root end and arranged to smoothly blend the outboard end of the wing into the substantially planar portion; and 
   a lower wing-like element smaller than the upper wing-like element and projecting downwardly with respect to the wing plane, the lower wing-like element including:
 a root end fixed to a lower surface of the curved transition portion at an intersection outboard of the upper wing-like element root end, the root end having a root chord that extends along only part of a chord of the upper wing-like element at the intersection, and 
 a trailing edge substantially adjacent the trailing edge of the upper wing-like element. 
   
     
     
         32 . The wing tip device according to  claim 31 , wherein the upper wing-like element has continuously decreasing chord from the root chord of the upper wing-like element to the tip chord. 
     
     
         33 . The wing tip device according to  claim 31 , wherein the lower wing-like element forms an angle with a tangent of the lower surface of the curved transition portion such that the lower wing-like element projects downwardly from the intersection and extends in an outboard direction. 
     
     
         34 . The wing tip device according to  claim 33 , wherein the angle is greater than approximately 80 degrees. 
     
     
         35 . The wing tip device according to  claim 31 , wherein the upper trailing edge is swept backwards. 
     
     
         36 . The wing tip device according to  claim 31 , wherein the lower trailing edge is swept backwards. 
     
     
         37 . The wing tip device according to  claim 31 , wherein the transition portion has increasing curvature of local dihedral in an outboard direction. 
     
     
         38 . The wing tip device according to  claim 31 , wherein an included angle between the upper and lower wing-like elements at the intersection is less than, or equal to, 160 degrees. 
     
     
         39 . A wing tip device for fixing to an outboard end of a wing, the wing defining a wing plane, the wing tip device comprising:
 an upper wing-like element projecting upwardly with respect to the wing plane including:
 a root end for fixing to the outboard end of the wing and having a root chord approximately equal to an outboard end chord of the wing, 
 a tip having a tip chord, 
 a trailing edge, 
 a substantially planar portion, and 
 a curved transition portion beginning at the root end and arranged to smoothly blend the outboard end of the wing into the substantially planar portion; and 
   a lower wing-like element smaller than the upper wing-like element and projecting downwardly with respect to the wing plane, the lower wing-like element including:
 a root end fixed to a lower surface of the curved transition portion at an intersection outboard of the upper wing-like element root end, the root end having 
 a root chord smaller than a local chord of the upper wing-like element at the intersection, and 
 a trailing edge substantially adjacent the trailing edge of the upper wing-like element.