Method and electrohydraulic system for controlling a retractable landing gear of an aircraft, landing gear and aircraft

1 . An electrohydraulic system for controlling a landing gear of an aircraft, the landing gear comprising a plurality of retractable landing gear units each provided with at least one wheel,

wherein the system comprises:

at least two braking devices for braking the wheel(s) of at least two landing gear units;

one movement device per landing gear unit, for moving a landing gear unit relative to a housing of the aircraft; and

two hydraulic units, each of the two hydraulic units being hydraulically connected to the movement devices and to at least one of the braking devices, each hydraulic unit comprising a reservoir containing a fluid, as well as a pump driven by an electric pump motor and a distributor configured to distribute the fluid to the braking device(s) and to the movement devices.

2 . The system according to claim 1 ,

wherein the system comprises only two braking devices, that are hydraulically supplied respectively by the two hydraulic units.

3 . The system according to claim 1 ,

wherein the system comprises only two braking devices that are hydraulically supplied jointly by the two hydraulic units.

4 . The system according to claim 1 ,

wherein the landing gear comprises three landing gear units, and the two hydraulic units are hydraulically connected to the movement devices associated with the three landing gear units.

5 . The system according to claim 1 ,

wherein the movement devices each comprise a piston integral with a rod and a hollow cylinder, the cylinder comprising an extension chamber and a retraction chamber separated by the piston, the distributor of each of the hydraulic units comprises:

a braking valve, hydraulically connected to the pump of this hydraulic unit and to at least one of the braking devices, in order to distribute the fluid contained in the reservoir of this hydraulic unit to the braking device(s);

an extension valve, hydraulically connected to the pump of this hydraulic unit and to the extension chambers of the movement devices, in order to distribute the fluid contained in the reservoir of this hydraulic unit into the extension chambers;

a retraction valve, hydraulically connected to the pump of this hydraulic unit and to the retraction chambers of the movement devices, in order to distribute the fluid contained in the reservoir of this hydraulic unit into the retraction chambers;

a first discharge valve, hydraulically connected to the reservoir of this hydraulic unit and to the extension chambers of the movement devices, in order to discharge the fluid contained in the extension chambers into the reservoir of this hydraulic unit; and

a second discharge valve, hydraulically connected to the reservoir of this hydraulic unit and to the retraction chambers of the movement devices, in order to discharge the fluid contained in the retraction chambers into the reservoir of this hydraulic unit.

6 . The system according to claim 5 ,

wherein the distributors comprise four check valves associated in series with the extension, retraction and discharge valves respectively.

7 . The system according to claim 5 ,

wherein the distributor comprises a single electric distribution motor controlling combined openings and closings of the braking, extension, retraction and discharge valves.

8 . The system according to claim 5 ,

wherein the distributor comprises a first electric control motor controlling opening and closing of the braking valve and a second electric control motor controlling combined openings and closings of the extension, retraction and discharge valves.

9 . A method for controlling the electrohydraulic system according to claim 5 , the method comprising the following steps:

supplying pressurized fluid to the distributor of each hydraulic unit by means of the pump of the respective hydraulic unit;

extending the movement devices, the braking valves being closed, the extension valves and the second discharge valves being open, the retraction valves and the first discharge valves being closed;

supplying the braking devices, the braking valves being open, the extension and retraction valves being closed; and

retracting the movement devices, the braking valves being closed, the retraction valves and the first discharge valves being open, the extension valves and the second discharge valves being closed.

10 . The control method according to claim 9 ,

the method comprising a post-extension balancing carried out following the extension, in order to balance the amounts of the fluid contained in the reservoirs of the hydraulic units, the distributors comprising four check valves respectively associated, in series, with the valves;

the post-extension balancing comprising the following steps:

detecting a first hydraulic unit containing the largest amount of fluid from among the hydraulic units, the other hydraulic unit being a second hydraulic unit;

activating the pump of the first hydraulic unit;

opening the extension valve and the second discharge valve of the first hydraulic unit and the first and second discharge valves of the second hydraulic unit;

closing the retraction valve and the first discharge valve of the first hydraulic unit and the extension and retraction valves of the second hydraulic unit;

detecting that the reservoirs of the first and second hydraulic units contain the same amount of fluid to within a margin; and

deactivating the pump of the first hydraulic unit.

11 . The method according to claim 9 ,

the method comprising post-retraction balancing, following the retraction, in order to balance the amounts of the fluid contained in the reservoirs of the hydraulic units, the distributors comprising four non-return valves respectively associated, in series, with the extension, retraction and discharge valves;

the post-retraction balancing comprising the following steps:

detecting a first hydraulic unit containing the largest amount of fluid from among the hydraulic units, the other hydraulic unit being a second hydraulic unit;

activating the pump of the first hydraulic unit;

opening the retraction valve and the first discharge valve of the first hydraulic unit and the first and second discharge valves of the second hydraulic unit;

closing the extension valve and the second discharge valve of the first hydraulic unit and the extension and retraction valves of the second hydraulic unit;

detecting that the reservoirs of the first and second the same amount of fluid to within a hydraulic units contain margin; and

deactivating the pump of the first hydraulic unit.

12 . The method according to claim 9 ,

the detections comprising:

measuring the amounts of fluid contained in the reservoirs of the hydraulic units;

comparing the amounts;

determining the first hydraulic unit, the reservoir of which contains the most fluid; and

determining that the reservoirs of the hydraulic units contain the same amount of fluid to within a margin.

13 . The method according to claim 9 ,

the method comprising a nominal configuring of the valves, the pumps being deactivated, the nominal configuration comprising:

closing the extension and retraction valves; and

opening the braking valve and the first and second discharge valves.

14 . An aircraft comprising a landing gear comprising at least two retractable landing gear units each provided with at least one wheel, the aircraft comprising the electrohydraulic system for controlling a landing gear according to claim 1 .