Method and device for lightening loads on the wing system of an aircraft in roll motion
A device used in an aircraft with an electrical flight control system to reduce load applied to the wing during a lateral roll maneuver, by comparing a roll control with a threshold, and filtering a control. As a result of this action on the roll control, resulting load increases on the wing can be anticipated and reduced. Loads can thus remain below a maximum design value for the wing if the applied roll control is too high for planned use of the aircraft, therefore limiting overdesign of the wing.
1. A method for reducing loads on a structural element of an aircraft due to a control parameter comprising:
comparing the parameter with a threshold value of the parameter;
when the parameter is less than or equal to the threshold value, applying a control value to the device corresponding to the control parameter;
when the parameter exceeds a threshold value:
filtering the difference between the parameter and the threshold value using a low-pass filter with a first time constant, and
applying a control order to the device corresponding to the sum of the filtered difference and a control value corresponding to the threshold value.
2. A method according to claim 1 , in which the control order corresponds to the parameter or the threshold value filtered by a low-pass filter with a second time constant.
3. A method according to claim 2 , in which the second time constant is less than the first constant.
4. A method according to claim 2 , wherein the aircraft is a civilian aircraft and the second time constant is non-zero.
5. A method according to claim 4 , wherein the second time constant is 1.2 seconds and the first time constant is 0.1 seconds.
6. A method according to claim 2 , wherein the aircraft is a military aircraft and the second time constant is zero.
7. A method according to claim 6 , wherein the first time constant is 0.6 seconds.
8. A method according to claim 1 , in which the control parameter is roll rate.
9. A method according to claim 1 , in which the threshold value is less than 100% of the control corresponding to a allowable maximum load.
10. A method according to claim 1 , wherein comparing is performed continuously.
11. A device for reducing load on a structural element of an aircraft due to a control, comprising:
an electrical control system configured to determine a control parameter;
an aircraft computer configured to calculate the difference between the control parameter and a threshold value of the control parameter; and
a first low-pass filter to filter the calculated difference if the difference is positive;
wherein the aircraft computer is configured to determine a control order that corresponds to the control parameter if the calculated difference is negative, and the aircraft computer is configured to determine the control order that corresponds to a sum of the filtered difference and a control value corresponding to the threshold value if the difference is positive.
12. A device according to claim 11 , further comprising a second low-pass filter, to determine the control order corresponding to a value by filtering.
13. A device according to claim 11 , further comprising a control system to apply the control order to a control surface.
14. A device according to claim 11 , wherein the electrical control system is connected to a control device, or an aircraft stick, and to a control surface, or an aircraft aileron.