Aircraft wing and wing tip device

1. An aircraft wing comprising a fixed wing and a wing tip device at a tip of the fixed wing, the wing tip device is rotatable relative to the fixed wing between:

a flight configuration for use during flight, and

a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that a span of the wing is reduced,

wherein the aircraft wing comprises a gear assembly coupling the wing tip device to an actuator such that the actuator drives rotation of the wing tip device between the flight and ground configurations,

wherein the gear assembly comprises a worm drive including worm gear configured to rotate about an input axis and a worm gear configured to rotate about an output axis, and the input axis is obtuse to the output axis,

wherein the worm gear is driven by the worm, and

wherein the worm gear comprises helical teeth and the helical teeth each form a portion of a helix extending around the output axis.

2. The aircraft wing according to claim 1 , wherein the wing tip device is rotatably coupled to the fixed wing by a rotational joint comprising a follower rotationally fixed relative to the wing tip device and a guide rotationally fixed relative to the fixed wing such that as the wing tip device rotates, the follower is rotated relative to the guide, and

wherein the follower or guide comprises a toothed rack that forms part of the gear assembly.

3. The aircraft wing according to claim 2 , wherein the follower comprises the toothed rack.

4. The aircraft wing according to claim 2 , wherein the toothed rack is coupled to the worm gear of the worm drive via an intermediate gear.

5. The aircraft wing according to claim 2 , wherein the worm gear meshes with the toothed rack.

6. The aircraft wing according to claim 1 , wherein the output axis is substantially parallel to an axis of rotation of the wing tip device.

7. The aircraft wing according to claim 1 , wherein the actuator comprises an output shaft that rotates about a rotational axis and is coupled to the worm of the worm drive to rotate the worm about an input axis, and wherein the rotational axis of the output shaft of the actuator is offset from the input axis of the worm of the worm drive.

8. The aircraft wing according to claim 1 , wherein the wing tip device and the fixed wing arc separated along an oblique cut plane passing through the upper and lower surfaces of the wing, the oblique cut plane is orientated normal to an axis of rotation of the wing tip device.

9. An aircraft wing comprising a fixed wing and a wing tip device at a tip of the fixed wing, the wing tip device is rotatable relative to the fixed wing between:

a flight configuration for use during flight, and

a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that a span of the wing is reduced,

the wing tip device is rotatably coupled to the fixed wing by a slew-ring,

the aircraft wing comprising a gear assembly that couples the wing tip device to an actuator such that the actuator drives the rotation of the wing tip device between the flight and ground configurations,

wherein the gear assembly comprises a worm drive includes a worm and worm gear driven by the worm;

wherein the worm is configured to rotate about an input axis parallel to a rotational axis of the wing tip device;

wherein the worm gear is configured to rotate about an output axis obtuse to the input axis, and

wherein the worm gear comprises helical teeth each forming a portion of a helix extending around the output axis.

10. The aircraft wing according to claim 1 , wherein the wing tip device is a wing tip extension.

11. An aircraft comprising the aircraft wing according to claim 1 .

12. A kit of parts of an aircraft wing, the kit of parts comprising a fixed wing and a wing tip device configured for attachment to a tip of the fixed wing such that the wing tip device is rotatable relative to the fixed wing between:

a flight configuration for use during flight, and

a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that a span of the wing is reduced,

wherein the kit of parts further

comprises:

an actuator, and

a gear assembly configured to couple the wing tip device to the actuator such that the actuator drives the rotation of the wing tip device between the flight and ground configurations,

wherein the gear assembly comprises a worm drive including an worm configured to rotate about an input axis and worm gear driven by the worm and configured to rotate about an output axis obtuse to the input axis, and

wherein the worm gear comprises helical teeth, and each of the teeth is shaped as a partial helix extending around the output axis.

13. A method of changing the configuration of an aircraft wing, the aircraft wing comprising a fixed wing and a wing tip device at a tip of the fixed wing, the wing tip device is rotatable relative to the fixed wing between:

a flight configuration for use during flight, and

a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that a span of the wing is reduced,

wherein a gear assembly couples the wing tip device to an actuator such that the actuator drives the rotation of the wing tip device between the flight and ground configurations, and

wherein the gear assembly comprises a worm drive including worm configured to rotate about an input axis and a worm gear driven by the worm and configured to rotate about an output axis obtuse to the input axis and wherein the worm gear comprises helical teeth each forming a partial helix around the output axis, and

the method comprises rotating the wing tip device between the flight and ground configurations using the actuator, wherein the wing tip device rotates about an axis parallel to the output axis.

14. The aircraft wing according to claim 1 , wherein the output axis is parallel to a rotational axis of the wing tip device.