Apparatus, aircraft and method for moving a wing tip device away from a load-alleviating configuration

1. An aircraft comprising a wing, the wing having a fixed wing and a wing tip device moveably mounted to the fixed wing, wherein the wing tip device is movable from:

(a) a load-alleviating configuration in which the wing tip device is oriented relative to the fixed wing such that at least one of an upper surface and a lower surface of the wing tip device is positioned away from a corresponding upper or lower surface of the fixed wing, to

(b) a flight configuration in which the upper and lower surfaces of the wing tip device are continuations of the upper and lower surfaces, respectively, of the fixed wing,

wherein the wing tip device comprises an airflow channel extending between respective apertures on the upper surface and lower surface of the wing tip device, and wherein the airflow channel is configurable between:

(i) an open state which is configured to allow airflow through the channel from one of the upper surface or the lower surface of the wing tip device to the respective one of the upper surface or the lower surface of the wing tip device, via the apertures, and

(ii) a closed state in which the airflow through the channel, via the apertures, is blocked,

the channel being configured such that when the wing tip device is in the load-alleviating configuration and the channel is in the open state, the aerodynamic loading on the wing tip device in flight urges the wing tip device towards the flight configuration.

2. The aircraft according to claim 1 wherein when the channel is configured such that in the open state, the airflow flows through the channel from the lower surface of the wing tip device to the upper surface of the wing tip device.

3. The aircraft according to claim 1 , wherein the aperture on the upper surface is downstream of the aperture on the lower surface.

4. The aircraft according to claim 1 , wherein the airflow channel comprises an interior wall, to define a conduit extending between the apertures, and wherein the interior wall is shaped such that when the channel is in the open state, the aerodynamic loading on the wing tip device in flight urges the wing tip device towards the flight configuration.

5. The aircraft according to claim 4 , wherein the interior wall is contoured to create a relatively low pressure airflow flow through the channel compared to a relatively high pressure airflow over the upper surface of the wing tip device.

6. The aircraft according to claim 5 , wherein the channel separates the wing tip device into a forward portion, upstream of the channel, and a rearward portion downstream of the channel, and the channel is configured such that when the wing tip device is in the load-alleviating configuration and the channel is in the open state, the airflow around the forward portion in flight, creates an aerodynamic force urging the wing tip device towards the flight configuration.

7. The aircraft according to claim 1 , wherein the wing tip device further comprises a first door and second door, each door being operable to selectively open or close a respective aperture on the upper or lower surface of the wing tip device, to switch the channel between the open and closed states.

8. The aircraft according to claim 1 , wherein the wing tip device further comprises a deployable spoiler for deploying when the channel is in the open state, such that when the wing tip device is in the load-alleviating configuration, the channel is in the open state and the spoiler is deployed, the aerodynamic loading on the wing tip device in flight urges the wing tip device towards the flight configuration.

9. The aircraft according to claim 1 , wherein the wing tip device is rotatably mounted on a hinge at the tip of the fixed wing, such that it may rotate, about the hinge, between the flight configuration and load-alleviating configuration.

10. The aircraft according to claim 9 , wherein the aircraft comprises a restraining assembly operable between a restraining mode in which the wing tip device is held in the flight configuration using a restraining force, and a releasing mode in which the restraining force on the wing tip device is released, such that the wing tip device is able to adopt the load-alleviating configuration.

11. The aircraft according to claim 9 , wherein the channel is configured such that when the wing tip device is in the load-alleviating configuration and the channel is in the open state, the aerodynamic loading on the wing tip device in flight, creates a bending moment about the hinge, thereby urging the wing tip device to rotate towards the flight configuration.

12. The aircraft according to claim 1 , wherein the aircraft further comprises an actuator arranged to actuate the wing tip device from the load-alleviating configuration to the flight configuration, in conjunction with the aerodynamic forces on the wing tip device when the channel is in the open state, and wherein the actuator has a capacity of less than that required for moving the wing tip device when the channel is in the closed state.

13. A wing tip device for use as a the wing tip device on the aircraft of claim 1 .

14. A method of returning a rotatably mounted wing tip device from a load-alleviating configuration, to a flight configuration,

wherein the method comprises:

configuring, when the wing tip device is in the load-alleviating configuration, the wing tip device from:

(i) a closed state in which the airflow through a channel extending between apertures on the upper surface and lower surface of the wing tip device, is blocked, and

(ii) an open state in which airflow through the channel, via the apertures, is permitted, such that the aerodynamic loading on the wing tip device in flight urges the wing tip device to rotate towards the flight configuration.

15. A rotatably mounted wing tip device configured to return from a load-alleviating configuration to a flight configuration under the action of aerodynamic forces in flight, the wing tip device comprising a conduit extending between respective openings on upper and lower surfaces of the wing tip device, and the conduit being configurable between:

(i) a closed state in which the respective openings are blocked to prevent airflow through the conduit, and

(ii) an open state in which the respective openings are exposed such that air may flow through the conduit from the lower surface of the wing tip device to the upper surface of the wing tip device such that the aerodynamic loading on the wing tip device in flight urges the wing tip device to rotate towards the flight configuration.