Structure for attaching a landing gear to an aircraft fuselage

Details Structure for attaching a landing gear to an aircraft fuselage Structure for attaching a landing gear to an aircraft fuselage

2000-04-25

2001-08-14

Jordan, Charles T. (Department: 3644)

Aeronautics and astronautics

Landing gear

C244S1020SS

Reexamination Certificate

active

06273364

ABSTRACT:

DESCRIPTION
Technological Field
The invention relates to a structure for attaching landing gear positioned under the fuselage of an aircraft, through which forces borne by the landing gear, when it is lowered and in contact with the ground, are transferred to the fuselage.
The invention is applicable to any type of aircraft. However, it more particularly relates to wide-bodied aircraft, to which at least two sets of landing gear are fitted under the fuselage, on each side of at least one ventral beam that forms an integral part of the fuselage.
State of the Technology
The main function of landing gear fitted to aircraft is to distribute the aircraft load when it is on the ground, that is to say, during the phases of taxiing, taking off and landing. As such, the structure for attaching the landing gear to the fuselage must be capable of integrally supporting the load borne by the landing gear when the aircraft is not in flight. In effect, it is through the structure for attaching the landing gear to the aircraft structure that the forces borne by the landing gear are transmitted to the fuselage.
If an orthonormal datum point OXYZ is associated with the aircraft, at which the axes OX, OY and OZ coincide respectively with longitudinal, transverse and vertical axes of the aircraft, the main forces which re applied to the landing gear of the aircraft are orces directed along the axes OX, OY and OZ as well as torsional moment when the aircraft turns.
A first known structure for attaching landing gear to the structure of an aircraft is illustrated, in a very diagrammatic fashion, in
FIG. 1
of the appended drawings. This type of assembly is used, notably on the Boeing 747 wide bodied aircraft, to connect each of the sets of landing gear positioned underneath it, to the fuselage.
In such a structure, the ends of a barrel
1
connected to the landing gear, are received in two fixed bearings
2
and
3
, supported by the fuselage. In the case of landing gear positioned laterally under the fuselage, the outside bearing
2
is connected directly to the fuselage and the inside bearing
3
is mounted in a ventral beam which forms an integral part of the fuselage.
As has been diagrammatically illustrated in
FIG. 1
, means
4
are provided, in this case, to axially immobilize the barrel
1
in the outside bearing
2
mounted directly in the fuselage of the aircraft. When such an attachment structure is used, the longitudinal and vertical forces exerted along axes OX and OZ symmetrically pass through the two bearings
2
and
3
, while the lateral forces exerted along the axis OY only pass through the outside bearing
2
. The part of the fuselage in which the outside bearing
2
is mounted and the ventral beam in which the inside bearing
3
is mounted are then dimensioned in such a way as to be able to take up the forces that are liable to be transmitted to each of these bearings.
During the design of a new aircraft, the ventral beam in which the inside bearing
3
is mounted, can be dimensioned so that this beam is capable of efficiently taking up all the structural forces applied to the fuselage during the flight (flexion, torsion, etc.). The part of the fuselage in which the outside bearing
2
is mounted then no longer needs to be reinforced.
Under these conditions, the use of an attachment structure such as the one illustrated in
FIG. 1
is excluded. In effect, the non-reinforced nature of the part of the fuselage in which the outside bearing
2
would be mounted, does not permit transfer to the aircraft structure, of the forces borne by the landing gear when the aircraft is on the ground in a sure fashion. Furthermore, it is not envisaged that the dimensioning of the part of the fuselage that supports the outside bearing
2
should be increased so that this part of the fuselage can ensure, without risk, the transmission of the forces borne by the landing gear to the structure of the aircraft. In effect, this would lead to dimensions that are too great, notably with regard to the thickness, as well as to an unacceptable increase in cost and in mass.
An inversion of the assembly illustrated in
FIG. 1
could be envisaged, that is to say that the bearing
2
is mounted in the ventral beam of the aircraft and the bearing
3
in the fuselage structure. However, this would require a significant reinforcement of the part of the attachment situated at the side of the ventral beam. The consequent increase in the mass of the attachment which would arise from this will also run contrary to the desired goal.
It should be noted, in addition, that the type of attachment structure illustrated in
FIG. 1
, leads to the creation of a disymmetrical barrel. This requires one to use two different dies to manufacture the barrels for the sets of landing gear positioned under the fuselage. Taking account of the very expensive nature of this component, this constitutes a notable disadvantage from the economic point of view.
Finally, the assembly illustrated in
FIG. 1
also has the disadvantage that the assembly is difficult to produce if the two bearings
2
and
3
are not perfectly aligned, because of the fixed nature of these bearings.
In
FIG. 2
of the appended drawings, a second known type of structure for attaching landing gear has been shown in very diagrammatic fashion. In this case, the barrel
1
is supported at each of its ends by two ball joints
5
and
6
. On a wide bodied aircraft, these ball joints
5
and
6
are respectively mounted in the structure of the fuselage and in a ventral beam forming an integral part of the fuselage. The connection between the barrel
1
and each of the ball joints
5
and
6
is made in a totally symmetrical fashion, using two clamping components
7
and
8
. These clamping components
7
and
8
are suitable for transmitting the lateral forces along the axis OY respectively to ball joint
5
and to ball joint
6
, depending on whether the forces are exerted towards the outside (to the left in
FIG. 2
) or towards the inside of the aircraft.
In comparison with the type of attachment structure previously described and with reference to
FIG. 1
, this assembly has the advantages of being symmetrical and easy to assemble.
Nevertheless, it leads, like the previous structure, to the transmission of forces along the axis OY directly to the fuselage, through the clamping component
7
and the external ball joint
5
, when these forces are directed toward the outside of the aircraft. As has already been observed, this layout is not satisfactory in the case of an aircraft of new design, the ventral beam of which has been dimensioned in such a way that it takes up all the structural forces which are applied to the fuselage during the flight and in which, as a consequence, the fuselage is not reinforced at this point.
DESCRIPTION OF THE INVENTION
The precise subject of the invention is a structure for attaching landing gear positioned under the fuselage of an aircraft, that permits the transmission to a ventral beam connected to the fuselage, the set of lateral forces borne by the landing gear so that it is not necessary to reinforce the structure of the fuselage in the area of attachment of the landing gear, and without, for all that, increasing either the mass of the aircraft or its cost.
Conforming to the invention, this result is obtained by means of a structure for the attachment of landing gear to an aircraft fuselage, said structure comprising a barrel connected to the landing gear, the ends of which, turned towards the inside and towards the outside of the aircraft, are supported respectively by a ventral beam and by a lateral fitting connected to the fuselage, a structure characterized in that it further comprises a force take-up bar, which connects the lateral fitting to the ventral beam coaxially with the barrel, in such a way as to transmit, to the ventral beam, forces exerted by the barrel on the lateral fitting along the axis of the barrel and towards the outside of the aircraft.
Advantageously, each of the ends of the barrel is supported respectively by

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