Method for operating a landing gear assembly with a breaker strut

This application is a National Stage of International Application No. PCT/EP2010/057778 filed Jun. 3, 2010, claiming priority based on French Patent Application Nos. 09-02721, filed Jun. 5, 2009, the contents of all of which are incorporated herein by reference in their entirety.

The invention relates to a novel method of operating a landing gear with a folding strut. The term “operating” is used to mean moving the landing gear between its deployed position and its retracted position, or vice versa.

Landing gears are known that are pivotally mounted on an aircraft structure to move between a retracted position and a deployed position, the landing gear being stabilized in the deployed position by a brace member including at least one folding strut having two hinged-together links that, when the landing gear is in the deployed position, are held substantially in mutual alignment by a stabilizer member, itself comprising two hinged-together links that are likewise held substantially in mutual alignment by a locking member.

The strut is attached firstly to the leg of the landing gear and secondly to the structure of the aircraft, while the stabilizer member is attached firstly to the strut and secondly to the leg, or to the structure of the aircraft.

It is known to cause the landing gear to move by means firstly of a raising actuator, e.g. an actuator coupled to the leg of the landing gear, and secondly by an unlocking actuator serving to counter the locking member.

Thus, starting from the deployed position, the unlocking actuator is actuated first and it acts against the locking member so as to force the two links of the stabilizer member to move out of alignment, thereby consequently forcing the two links of the strut to move out of alignment. When moved out of alignment in this way, they can no longer oppose raising of the landing gear driven by the action of the raising actuator. Thus, raising such a landing gear requires two actuators.

Landing gears having folding struts are also known in which the two links of the strut are stabilized in an aligned position by means of return springs that keep the links in an aligned position that is defined by an internal abutment between the two links. In this type of landing gear, it is known to cause the landing gear to be raised by using a single actuator that acts on that one of the links that is hinged to the structure of the aircraft. The actuator causes the associated link to turn against the return springs. As it continues to turn, it causes the landing gear to move under drive from the links that, although out of alignment, continue to be connected to each other. Thus, the same actuator unlocks and raises the landing gear.

Nevertheless, such a configuration is suitable only for landing gears that do not include a member for stabilizing the alignment. In a landing gear having a folding strut that is stabilized by a stabilizer member itself having two links, the lifting actuator attached to one of the links of the strut is not capable of moving the links of the stabilizer member out of alignment, thereby preventing any movement of the landing gear.

The invention seeks to propose a simple method of operating a landing gear having a folding strut and an alignment stabilizer member.

In order to achieve this object, there is provided a method of operating an aircraft landing gear between a deployed position and a retracted position, the landing gear comprising a leg hinged to the aircraft, the leg being stabilized in the deployed position by a folding strut comprising two hinged-together links, the strut being held in an aligned position by a stabilizer member comprising two hinged-together links, themselves held in alignment by a locking member. According to the invention, the method includes the steps of arranging the strut and the stabilizer member in such a manner that at least one of the links of the stabilizer member moves continuously during a movement of the leg from the deployed position to the retracted position, and of attaching an operating actuator to said link in order to cause the link to pivot against the locking member and to exert thereon a force tending to move the leg.

Thus, the operating actuator acts simultaneously to move the links of the stabilizer member out of alignment against the locking member, thereby moving the links of the strut out of alignment, and also driving pivoting of the leg of the landing gear, since the links of the stabilizer member, the links of the strut, and the leg all form parts of a common linkage.

The fact that the movement of the actuated link is continuous serves to ensure that the landing gear is raised by means of action that is continuous and in the same direction of the actuator. The actuator may equally well be of the linear type or of the rotary type, providing it is compatible with the amplitude of the movement performed by the actuated link.

The invention can be better understood from the light of the description of the figures of the accompanying drawings, in which:

FIG. 1 is a side view of a landing gear applying the provisions of the invention, shown here in the deployed position;

FIGS. 2 to 4 are skeleton side views of the FIG. 1 landing gear showing it in various stages while being raised, i.e. in the deployed position, in an intermediate position, and in the retracted position; and

FIG. 5 is a view analogous to FIG. 1 for a variant embodiment of the invention.

With reference initially to FIG. 1 , the landing gear comprises in conventional manner a leg 1 hinged to the structure of the aircraft about a hinge axis X (seen end-on in the figure) so as to be movable between a deployed position (as shown in the figure) into which the landing gear is put prior to making a landing, and a retracted position, which is the position of the landing gear in flight.

A folding strut 2 is hinged firstly to the leg 1 and secondly to the structure of the aircraft. The folding strut 2 comprises two links 2 a and 2 b that are hinged together via a knee 3 . The link 2 a is also hinged to the aircraft, while the link 2 b is hinged to the leg 1 . The folding strut 2 is stabilized in a substantially-aligned position by means of a stabilizer member 4 comprising two links 4 a and 4 b that are likewise hinged together. The link 4 a is hinged to the leg 1 and the link 4 b is hinged to the strut 2 . The links 4 a and 4 b are held in a substantially-aligned position by a locking member 5 having return springs 6 urging the links 4 a and 4 b towards the locking position as defined by abutments 7 a and 7 b . When stabilized in this way, the folding strut 2 opposes any pivoting of the leg 1 about its hinge axis X, such that the deployed position is a stable position.

As is well known, the links 2 a , 2 b and the links 4 a , 4 b are designed in such a manner that in order to reach the locked position shown in the figure the hinged knee between each pair of links needs to go a little beyond the geometrically-aligned position as shown in dashed lines.

According to the invention, an operating actuator 10 is arranged on the structure of the aircraft for coupling to the link 4 a of the stabilizer member 4 , i.e. the link that is hinged to the leg 1 . The operating actuator 10 in this example is of the rotary type and includes a crank that is coupled to the link 4 a by means of a rod 8 .

The operation of the assembly is described below with reference to FIGS. 2 to 4 . When the landing gear is to be raised into the retracted position, the operating actuator 10 is put into operation. It exerts traction on the link 4 a (see arrow), thereby causing it to pivot about its pivot axis relative to the leg, thereby breaking the alignment between the links 4 a and 4 b against the action of the return springs 6 of the locking member 5 .

Since the link 4 b is attached to the strut 2 , the alignment of the links 2 a and 2 b is also broken. The landing gear is thus unlocked and can be pivoted about its hinge axis under drive from the operating actuator 10 , as shown in FIG. 3 .

As the operating actuator 10 continues to cause the link 4 a to pivot, it entrains in succession the other link 4 b , the links 2 a and 2 b of the strut 2 , and finally the leg 1 of the landing gear. All of these elements are coupled together so that any angular position of the link 4 a corresponds to one and only one position for each of the elements.

The movement continues to the position shown in FIG. 4 , with the leg 1 in its retracted position.

It is important to ensure that during the movement of the landing gear from its deployed position to its retracted position, the link 4 a moves continuously and without any singularity, such that the movement of the leg can be ensured by means of the operating actuator 10 acting continuously and always in the same direction on the link 4 a . Thus, with a single actuator, it is ensured that the stabilizer member is moved out of alignment, thereby enabling the strut to be moved out of alignment, and consequently allowing the leg to be moved.

In order to lower the landing gear into the deployed position, this may be done under the effect of gravity, with the operating actuator 10 being controlled for the purpose of regulating the downward speed of the landing gear. The movement of the link 4 a , which is continuous and without singularity in the raising direction, is therefore continuous and without singularity in the lowering direction, such that the operating actuator is always driven in the same direction while the landing gear is being lowered, and it therefore operates as a generator, thus enabling it to be used as a brake during lowering. To do this, it is naturally appropriate for the operating actuator to be reversible and to be capable of being driven by the link 4 a while the landing gear is being lowered.

In a variant shown in FIG. 5 , where elements in common with those of FIG. 1 have the same references plus one hundred, the operating actuator 110 is still a rotary actuator, but it is placed directly on the pivot axis of the link 104 a in order to drive it directly in pivoting. It should be observed here that the link 104 a is now hinged not to the leg, but directly to the structure of the aircraft. It should also be observed that the locking spring 106 is also attached to the structure of the aircraft, the locking position of the links 104 a and 104 b now being defined by an abutment 107 arranged on the structure of the aircraft to stop the link 104 a in the position shown in the figure, in which position it is substantially in alignment with the link 104 b.

Once more, unlocking and raising of the landing gear is ensured using a single actuator.

Preferably, the actuator is selected to be of the simplest and most reliable possible type. Where possible, it is preferable for the actuator to be of the torque motor type, capable of providing direct drive without gearing. Should gearing become necessary, it is possible to use a very reliable stepdown gear, e.g. of the deformable bell type, better known under the trade name “harmonic drive” that does not present a breakdown mode in which it jams.

The invention is not limited to the above description, but on the contrary covers any variant coming within the ambit defined by the claims.

In particular, the abutment(s) defining the substantially-aligned position of the links of the stabilizer member may be placed either between the links as in the example of FIG. 1 , or on the structure of the aircraft for co-operating with the link that is actuated, as in the example of FIG. 5 ; however it could also co-operate with a moving portion of the actuator in order to stop it in a defined position, which position is confirmed by a spring member. Naturally, it is important for the actuator to be capable of moving the associated link against said spring member.

Furthermore, the operating actuator may be of the linear type, being coupled to one of the links of the stabilizer member, providing the stroke and the lever arms of such an actuator are compatible with raising the landing gear. The actuator may be of the electrical or of the hydraulic type.

In addition, although the actuator in the examples shown is fastened to the structure of the aircraft, it is also possible, still within the ambit of the invention, to attach the actuator directly to one of the elements of the landing gear, providing the actuator also remains attached to one of the links of the stabilizer member.