Method for operating an aircraft comprising a wing with a foldable wing tip portion

1. A method for operating an aircraft including a fuselage, wings mounted to the fuselage, a sensor system, and a control unit, wherein each wing includes a fixed wing and a foldable wing tip portion pivotably mounted to the fixed wing to fold about an axis of rotation between an extended position and a folded position, an actuation unit configured to actuate movement of the foldable wing tip portion between the extended position and the folded position, and an arresting unit configured to lock the foldable wing tip portion in the extended position and/or in the folded position, wherein the sensor system is configured to detect an operation parameter, and the control unit includes a system behavior model with respect to the operation parameter, wherein the system behavior model provides a target value of the operation parameter, and the method comprises:

actuating movement of the foldable wing tip portion towards the extended position or the folded position;

detecting a value of the operation parameter by the sensor system, wherein the operating parameter is related to the operation of the foldable wing tip portion;

comparing the detected value of the operation parameter to a corresponding target value of the operation parameter obtained from the system behavior model, and

if a deviation between the detected value and the target value exceeds a predefined deviation, generating a notice of a sensor failure or a system failure.

2. The method according to claim 1 , wherein the control unit comprises multiple system behavior models for multiple operation parameters, wherein each of the operation parameters relates to the operation of the foldable wing tip portion.

3. The method according to claim 1 , wherein the operation parameter relates to a time period of an actuation cycle of the actuation unit, wherein the actuation cycle includes movement of the wing tip portion between the extended position and the folded position.

4. The method according to claim 3 , wherein the time period of the actuation cycle is detected between starting an actuation command and reaching a desired position by the actuation unit.

5. The method according to claim 3 , wherein the time period of the actuation cycle is detected between starting an actuation command and locking the foldable wing tip portion in a desired position by the arresting unit.

6. The method according to claim 1 , wherein the operation parameter relates to a position of the foldable wing tip portion.

7. The method according to claim 1 , wherein the operation parameter relates to a speed movement of the foldable wing tip portion relative to the fixed wing.

8. The method according to claim 1 , wherein the operation parameter relates to a torque applied by the actuation unit to move the foldable wing tip portion.

9. The method according to claim 1 , wherein the system behavior model includes an algorithm calculating the target value of the operation parameter in dependence on other parameters detected by the sensor system, wherein the other parameters relate to the operation of the wing tip portion.

10. The method according to claim 9 , wherein the other parameters include one or more of: a time period of an actuation cycle, a position of the foldable wing tip portion, a speed of the foldable wing tip portion, a torque applied by the actuation unit, an external load and an external temperature.

11. The method according to claim 1 , wherein the system behavior model relates to a computer simulation of the target values of the one or more operation parameters during an actuation cycle or during a locking cycle of the wing tip portion, and the computer simulation takes into account one or more of the following operation parameters and external parameters: a time period of an actuation cycle, a position of the foldable wing tip portion, speed of the foldable wing tip portion, torque applied by the actuation unit, an external load and temperature.

12. The method according to claim 1 , further comprising issuing a warning in response to the detection of the sensor failure or the system failure.

13. The method according to claim 1 , wherein upon the detection of the sensor failure deactivating a corresponding sensor in the sensor system.

14. The method according to claim 1 , wherein in response to the detection of the system failure the respective system is stopped, operating a system corresponding to the system failure in a safe mode and/or deactivating the system.

15. An aircraft comprising:

a fuselage;

wings mounted to the fuselage, wherein each wing comprises a fixed wing, a foldable wing tip portion mounted to the fixed wing and configured to pivot about an axis of rotation between an extended position and a folded position;

an actuation unit configured to actuate movement of the foldable wing tip portion between the extended position and the folded position;

an arresting unit configured to lock the foldable wing tip portion in the extended position and/or in the folded position;

a sensor system configured to detect an operation parameter related to the operation of the foldable wing tip portion, and

a control unit which comprises a system behavior model with respect to the operation parameter, wherein the system behavior model provides a target value of the operation parameter, and wherein the control unit is configured for:

comparing a detected value of the operation parameter detected by the sensor system to a corresponding target value of the operation parameter from the system behavior model, and

upon a predefined deviation of the detected value from the corresponding target value of the operation parameter, detecting a sensor failure or a system failure.