Curved wingtip for aircraft

1. A curved planar wingtip, comprising:

a stationary wingtip attached to an outboard end of a wing of an aircraft,

wherein the stationary wingtip has a continuously curving planar member that extends aft of a trailing edge of the wing to form a tip;

the tip is substantially in the same plane as the wing without extending substantially upwardly or downwardly with respect to the wing;

wherein the stationary wingtip comprises:

an outboard edge that curves continuously with a finite radius of curvature from a wing leading edge to the tip;

an inboard edge that curves continuously with a finite radius of curvature from a wing trailing edge to the tip;

wherein the outboard edge and the inboard edge come together at the tip such that the tip is substantially pointed; and

wherein the outboard edge has a smaller radius of curvature near the wing leading edge and a gradually increasing radius of curvature as the outboard edge curves aft towards the tip; and

a span of the wingtip is at least twice the distance that the tip extends aft of the trailing edge.

2. The curved planar wingtip of claim 1 , wherein the tip extends aft of the trailing edge of the wing by a distance of at least ten percent of a tip chord of the wing.

3. The curved planar wingtip of claim 1 , wherein the induced drag of the wing is reduced by the curved planar wingtip without substantially increasing the lift of the wing and without substantially increasing the weight of the wing.

4. The curved planar wingtip of claim 1 , wherein the curved planar wingtip avoids applying substantial additional loads to the wing due to cross winds.

5. The curved planar wingtip of claim 1 , wherein the wing is a straight wing of the aircraft and the curved planar wingtip is substantially planar with the straight wing.

6. The curved planar wingtip of claim 1 , wherein the wing is a horizontal tail of the aircraft and the curved planar wingtip is substantially planar with the horizontal tail.

7. The curved planar wingtip of claim 1 , wherein the wing is a vertical tail of the aircraft and the curved planar wingtip is substantially planar with the vertical tail.

8. The curved planar wingtip of claim 1 , wherein the outboard edge and the inboard edge each curve continuously with elliptical radii to provide in-plane sweep from an end of the wing.

9. The curved planar wingtip of claim 8 , wherein the inboard edge angles aft of the trailing edge by an angle of twenty degrees with a line tangent to the curve of the inboard edge.

10. The curved planar wingtip of claim 8 , wherein the outboard edge comprises embedded navigational lights.

11. The curved planar wingtip of claim 1 , wherein the wing is a swept wing of the aircraft and the curved planar wingtip is substantially planar with the swept wing.

12. The curved planar wingtip of claim 11 , wherein the inboard edge extends in an aft direction from the trailing edge at an interface by an angle greater than a sweep angle of the swept wing.

13. The curved planar wingtip of claim 12 , wherein a trailing-edge sweep angle is twenty degrees greater than the sweep angle of the swept wing.

14. An aerodynamic device comprising:

a wingtip adapted to be either: fixed to an outboard end of an aircraft wing, or made to be integral with the wing, such that the wingtip provides a stationary extension from the outboard end of the aircraft wing;

the wingtip having a continuously curving planar portion that extends aft of a trailing edge of the wing, wherein the continuously curving planar portion forms a substantially pointed tip that is substantially in the same plane as the wing without extending substantially upwardly or downwardly;

the wingtip has an inboard edge that angles aft of the trailing edge of the wing by an angle of twenty degrees with a line tangent to the curve of the inboard edge; and

the wingtip has an outboard edge with a smaller radius of curvature near the wing and a gradually increasing radius of curvature as the outboard edge curves aft towards the tip.