Wing tip device

A method of modifying a wing tip device for 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, the method comprising:

• providing a substantially planar 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;
• and
• fixing the lower wing-like element to the upper wing-like element such that:
• the intersection between the lower wing-like element and the upper wing-like element is at an outboard end of the wing,
• wherein the upper wing-like element is larger than the lower wing-like element wherein the lower wing-like element is substantially planar,
• wherein 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,
• wherein when the aircraft is on the ground and the wing is subjected to downward deflection due to full fuel load, the wing is in a ground shape where one of the upper and lower wing-like element tips is located no further outboard than an airport compatibility gate limit such that the spanwise extent of the wing is no more than the airport compatibility gate limit, and
• wherein when the aircraft is in flight, the wing is in a flight shape that comprises the tip of the lower wing-like element extending further outboard, in the spanwise direction, than the tip of the upper wing-like element due to aeroelastic deformation of the wing shape, such that the lower wing-like element provides an increase in wingspan, the increase in wingspan is such that the spanwise extent of the wing in the flight shape is greater than the airport compatibility gate limit.