Front landing-gear well

A forward part of an aircraft comprising a fuselage and a landing gear well housing a forward landing gear comprising a breaker strut designed to adopt an extended configuration when the landing gear is extended, configuration in which said breaker strut lies in a strut plane parallel to the transverse direction of the forward part. The forward part comprises a transverse beam resisting strut reactions located above the landing gear well and mounted on the fuselage at its two ends, the beam having a globally rectangular cross-section, in which the median plane parallel to the length of the rectangle is coincident with said strut plane.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No. 11 58802 filed on Sep. 30, 2011, the entire disclosures of which are incorporated herein by way of reference.

BACKGROUND OF THE INVENTION

This invention relates to a forward part of an aircraft, also called the nose cone, comprising a landing gear well housing a forward landing gear.

The invention is applicable to all types of aircraft.

Many developments have been made to aircraft nose cones to optimize its mass, volume, cost, safety, ease of fabrication, maintenance, etc. One example of such a nose cone is disclosed in documents FR 2 910 875 and U.S. Pat. No. 7,784,736.

Despite the existence of many constructions, the environment of the nose cone landing gear well can still be optimized, particularly to distribute forces introduced by the front landing gear breaker strut.

Normally, the landing gear well is made by means of stiffened panels forming a housing isolated from the pressure, the well being surrounded by a network of frames that stiffen the fuselage frames. With this type of design, the panels forming the landing gear well have to be large to be able to resist forces from the forward landing gear, and particularly reactions from the breaker strut.

This creates disadvantages in terms of mass and volume, and makes it necessary to use a metallic material to manufacture panels of the landing gear well. Furthermore, the solution described above usually induces high mechanical loads in the forward zone of the windshield, which are obviously undesirable.

Furthermore, the nose cone can also be optimised so as to facilitate access by operators working on fabrication/handling of this very densely occupied part.

In particular, the high pressure zone located above the landing gear well that will contain a large amount of instruments/equipment, is often difficult to access for operators.

SUMMARY OF THE INVENTION

Therefore, the purpose of the invention is to at least partially overcome the disadvantages mentioned above dealing with embodiments according to prior art.

To achieve this, the primary purpose of the invention is the forward part of an aircraft consisting of a fuselage and a landing gear well comprising a forward landing gear with a breaker strut designed to adopt an extended configuration when the landing gear is extended, a configuration in which said breaker strut lies in a strut plane parallel to the transverse direction of the forward part. According to the invention, the forward part comprises a transverse beam resisting strut reactions located above the landing gear well and mounted on the fuselage at its two ends, said beam having a globally rectangular cross-section, in which the median plane parallel to the length of the rectangle is coincident with said strut plane.

The invention thus provides a simple solution for the transfer of reactions from the strut, by means of a beam shaped structural element oriented in the same plane as the extended breaker strut, and which participates in creating a more direct path of forces to the fuselage. This particular geometric layout assures a good resistance to strut reactions because these reactions can be routed to the ends of the beam by shear resistance, and are then distributed into the fuselage.

The invention can also make use of elements with simple geometries, suitable for manufacturing from a composite material preferably including a mix of resin and carbon fibers. The use of this material, particularly for the beam and the elements defining the landing gear well, results in a non-negligible mass saving.

The mass is also reduced by reducing the dimension of elements defining the landing gear well, which no longer need to fulfill the function of resisting reactions transferred from the breaker strut, in this case this function being performed by the special purpose beam. This mass reduction is naturally accompanied by a reduction in the volume of the landing gear well. This advantageously leads to an increase in surrounding pressurized volumes, allowing the integration of nose cone functions.

Finally, the invention very much limits the distribution of strut forces towards the forward windshield zone, which reduces risks of breakage of the windshield.

Preferably, the ratio between the length of the rectangular section of the beam and the length of this beam is between 3 and 6, and more preferably between 4 and 5, and/or the ratio between the length and the width of the rectangular section is between 8 and 12, and more preferably between 9 and 11. This structural element is thus in the form of a relatively short “plane beam”, with a high inertia in the plane of the forces in which it lies. The result is very small deformation of this beam, strut forces can be transferred directly to the ends of the beam through shear resistance.

Preferably, said strut force resistance beam extends from a top partition of the landing gear well down to a floor of said aircraft forward part. This can give or result in a tall beam that fits perfectly well into its environment without any need for a substantial modification to the architecture of the nose cone. The relatively large height of the beam due to its very short length, not only increases its stiffness but also reduces stress concentrations in the fuselage, since forces introduced into it are distributed over a larger interface. Therefore the distribution of forces is advantageously more uniform.

Preferably, said two ends of the beam are mounted on a skin of said fuselage, giving very good diffusion/dilution of forces in this fuselage. Preferably, this applies to the inner skin of the fuselage, even if the assembly could alternatively or simultaneously be made on fuselage frames.

Preferably, said beam has a lower longitudinal edge provided with means of assembly of said breaker strut. This can give or result in direct transfer of strut forces into the transverse beam. Alternately, the lower longitudinal edge of the beam could be installed on an intermediate structure that would itself support said means of mounting said breaker strut. This intermediate structure could for example be of the metallic insert type added onto the beam, which is preferably made of a composite material.

Furthermore as mentioned above, said beam is made of a composite material, preferably a mix of resin and carbon fibers, to save mass. Nevertheless it could be metallic without going outside the scope of the invention. Note that the partitions defining the landing gear well could also be made of a composite material.

According to another aspect of this invention, its purpose is a forward landing gear well for an aircraft comprising an upper partition comprising at least one removable cover closing off a manhole.

In this case the invention is remarkable in that it discloses use of the roof of the landing gear well to allow room for operators to pass through to perform fabrication/handling operations in the environment inside the landing gear well. In particular, it is preferably arranged so that the operator can stand upright in the landing gear well with his body passing through the manhole.

Thus, the invention eliminates some existing trapdoors, usually formed in the bottom part of the fuselage.

There are several possible configurations, namely a single manhole closed off by one or several removable covers, or several manholes closed off by the same removable cover, or each manhole closed off by one or several removable covers.

Secondly, the removable cover(s) may form all or some of the upper partition. This can thus be composed solely of covers or a single removable cover, or formed from one or several fixed upper panels with one or more openings forming manholes closed off by the removable covers.

Conventionally, the area of a manhole is larger than 0.225 m2, normally in the form of a 450 mm wide and 500 mm long rectangle. In the invention each manhole is preferably square or rectangular with an area of the order of 1 m2.

Preferably, the landing gear well comprises two opposite lateral partitions, each partition forming an integral part of a lateral box formed jointly with an upper panel connected firstly to the upper longitudinal edge of the lateral partition and secondly on the fuselage. Such lateral boxes can advantageously stiffen the perforated fuselage due to the presence of the forward landing gear well, and thus stiffen the lateral partitions of this forward landing gear well, in order to minimize their deformation.

To save mass, each removable cover is preferably in the form of a honeycomb sandwich structure. This structure may be identical to or similar to the composite structure conventionally adopted for articulated fuselage covers, closing off the lower part of the landing gear well.

Another purpose of the invention is a forward part of an aircraft comprising such a landing gear well housing a forward landing gear. Preferably, the forward part comprises one or several transverse stiffeners connected to the fuselage at their ends and routed close to the upper partition. These stiffeners also participate in stiffening the fuselage perforated at the forward landing gear well, and consequently limit forces to be resisted by the above-mentioned lateral boxes.

Preferably, the forward part comprises a forward landing gear comprising a deployment jack and a breaker strut both mounted on the lateral partitions of the landing gear well. This can very significantly reduce the weight of the removable covers of the roof of the landing gear well, considering that they no longer need to resist breaker strut forces and jack forces. Preferably, they are designed to resist pressure only, and can thus be small thickness, for example of the order of 100 mm thick when they are made of a carbon/Nomex™ sandwich. In other words, it is preferably arranged such that the removable covers do not have any direct mechanical link with the forward landing gear.

This solution with removable covers for the roof of the landing gear well may also be combined with the solution described above, integrating said transverse beam resisting reactions from the breaker strut.

Thus, said forward landing gear preferably comprises a breaker strut designed to adopt an extended configuration when the landing gear is extended, in which said breaker strut lies in a strut plane parallel to the transverse direction of the forward part, and the forward part also comprises a transverse beam to resist strut forces arranged above the landing gear well and mounted at its two ends on the fuselage, said beam having a globally rectangular section of which the median plane parallel to the length of the rectangle is coincident with said strut plane.

Finally, another purpose of the invention is an aircraft with a forward part of the type defined above.

Other advantages and characteristics of the invention will become clear after reading the detailed non-limitative description given below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the following description, by convention X is the longitudinal direction of the aircraft, Y is the direction transverse to the aircraft and Z is the vertical direction or the height, these three directions X, Y and Z being mutually orthogonal.

Furthermore, the terms “forward” and “aft” should be considered relative to the direction of motion of the aircraft that occurs as a result of the thrust applied by the turbojets, this direction being shown diagrammatically by the arrow3.

The forward part1comprises firstly a pressurized zone2in its aft most part within which there is a separation floor8between an upper pressurized compartment4usually dedicated to the transport of persons, and an underfloor pressurized compartment6usually dedicated to storage of technical equipment specific to the aircraft and/or to storage of the cargo. More precisely, the upper pressurized compartment4usually comprises, in the direction from the forward end towards the aft end, the aircraft cockpit7followed by the passenger cabin9. Furthermore, the pressurized underfloor compartment6usually comprises, from the forward end towards the aft end, a so-called technical hold for storage of technical equipment specific to the aircraft followed by a so-called cargo hold that will be used to store cargo.

The pressurized zone2is delimited at the forward end by a bulkhead10that functions jointly with the nose cone12of the fuselage15, to define a non-pressurized radome zone14in which the radar assembly16is located. The section of the bulkhead10is globally V-shaped open forwards, the ends of the V are fixed to the fuselage15and the apex facing in the aft direction is fixed to the forward end of the floor8. The upper part18of the bulkhead10delimits the forward part of the cockpit, while the lower part forms firstly a forward partition20of the unpressurised landing gear well22and secondly a panel21delimiting the underfloor pressurized compartment6, that passes partly above the landing gear well22.

The forward landing gear well is designed to house a forward landing gear30in its retracted state, different from the extended state shown diagrammatically inFIG. 1. The forward landing gear30is of the conventional type known to those skilled in the art. It generally includes a landing strut32installed articulated at one of its ends on the landing gear well and comprises a set of wheels34at its other end. It also comprises one or several extension jacks (not shown) and a breaker strut36usually made from two segments hinged to each other, the lower end of which is articulated onto the strut32. In the extended state of the landing gear shown inFIG. 1, the breaker strut36is designed to adopt an extended configuration in which the two segments are aligned, to lie in a strut plane P1parallel to the Y direction. This plane P1is inclined from the vertical, for example at an angle of between 20 and 50°.

According to one particular feature of the invention, the upper end of the breaker strut36is articulated on a transverse beam40resisting strut reactions. The beam40oriented along the Y direction has a globally rectangular cross-section shown inFIG. 1a, of which the median plane P1parallel to the length L1and perpendicular to the width L2of the rectangle is coincident with said strut plane P1.

The beam40is thin, so that it can be considered as “plane beam”. This thickness corresponding to the width L2of the above-mentioned rectangle may for example be of the order of 50 to 60 mm. This thickness is similar to the thickness of load-resisting structures in the landing gear well, particularly its sealed rear bulkhead that resists reactions from the forward landing gear. In this respect, note that the ratio between the length L1and the width L2of the rectangular section is preferably between 9 and 11, which symbolizes the “plane” shape of this beam. This gives it an excellent capacity to integrate forces from the center towards the ends, with minimum deformation. Furthermore, the beam40is short, in other words it has a large height to length ratio, which means that the ratio between the length L1of the rectangular section of the beam and the length L of this beam referenced inFIG. 2is preferably between 4 and 5. Typically, the length L1of the section, in other words the height of the beam, is of the order of 600 mm, while the length L of the beam along the Y direction is between 240 and 300 cm. The relative length of the beam could be even smaller, but in this case, it is arranged such that the beam extends along the vertical direction Z, occupying practically the entire space between the upper partition44of the landing gear well and the floor8.

With reference to the threeFIGS. 1 to 3, the figures show that the beam40, designed solely to resist forces introduced by the breaker strut36, is arranged above the landing gear well22and is installed fixed at its two ends on the fuselage15. These ends are preferably added onto the inner skin48separated from the outer skin50of the fuselage by transverse frames52. The beam could alternately be fixed to the frames52, forces finally being distributed through the fuselage skins. To achieve this, the connection method at the fuselage is preferably made of simple double angles (not shown) placed on the fuselage at the ends of the beam. The connection between the beam40and the angles consists of simple shear screws over the entire height of the edges of the beam. Excess material thicknesses may be provided at junctions between parts, to make them stiffer.

The beam40is thus dedicated exclusively to resisting reaction forces from the strut, while remaining connected to the fuselage at its ends only. Furthermore, the beam is provided with means of assembling the strut36at the median part of its lower longitudinal edge56, in this case in the form of devises60fixed to the edge56, and holding tenons60fixed to the upper end of the breaker strut36. Therefore, strut reactions do no pass into the upper partition of the landing gear well, but are inserted directly into the “plane beam” and then pass by shear towards the ends of the beam, before being distributed into the fuselage15.

The beam40can be made in different ways and from different materials. Firstly, it can be in the general form of a “plane box”, for example a genuine double skin box, in other words a parallelepiped shaped box made from six stressed external panels. Transverse ribs could also be integrated inside the box. This solution is preferred because it is mechanically very efficient, but another solution with a single skin could also be envisaged without going outside the scope of the invention.

For the choice of materials, metallic elements can be selected, or elements made of composite materials, preferably of the type comprising a mix of resin and carbon fibers. The composite may be of the monolithic type made by assembling parts by riveting, gluing of co-baking. The double skin solution itself may be made using a sandwich structure comprising a central honeycomb core enclosed between two composite skins.

Now with reference toFIGS. 2 to 4b, remember that the forward landing gear well22creates a large opening in the lower part of the fuselage. Thus the skins and frames are perforated to allow the forward landing gear to extend from and retract into the forward landing gear well. The well22is then open downwards, this opening being closed off by articulated covers that, when in the closed position, reform the aerodynamic surface of the missing part of the fuselage.

The well22is delimited by the forward partition20, an aft partition64, the upper partition44and two lateral partitions66opposite and facing each other.

Each of the lateral partitions66preferably extends approximately parallel to the X and Z directions over the entire length of the landing gear well22. Each of them forms an integral part of a lateral box68running longitudinally along the sides of the well22, being formed jointly with an upper panel70connected firstly to the upper longitudinal edge of the lateral partition66and secondly onto the fuselage15, preferably on the skins. Thus, each box68preferably has a globally quarter-circle shaped cross-section, with a radius corresponding to the radius of the outer skin of the fuselage50, as can be seen better inFIG. 3. This stiffens the fuselage that is perforated due to the presence of the forward landing gear well, and thus stiffens the lateral partitions in this forward landing gear well in order to better limit their deformation.

The forward part1is also provided with several transverse stiffeners connected to the fuselage at their ends and passing close to the upper partition44, in order to limit forces to be resisted by the boxes68.

In the illustrated preferred embodiment, the ends of a first transverse spar72shown inFIGS. 4aand 4bconnect two far portions of an interrupted fuselage frame52, passing close to the lower edge56of the beam40, above the upper partition44. The ends of a second transverse spar74, also shown inFIGS. 4aand 4b, also connects two far portions of an interrupted fuselage frame52, passing close to a landing wheel housing and the upper edge of the beam40, in other words close to the floor8. This same edge may bear on the second spar74as shown in the figures.

Another special feature of this invention lies in the fact that the upper partition44comprises removable covers that release/close off manholes. In the preferred embodiment shown, a forward removable cover44aand an aft removable cover44bare provided, each installed removably around the periphery of the well. In this case, these two covers44a,44bshown inFIGS. 4aand 4bmake up the entire part of the upper partition44. They may both be convex upwards, so as to house the forward landing gear in its retracted state. They are installed reversibly at their periphery, which means that they are also mounted one above the other at their junction, for example close to the first transverse stiffener spar72.

For example, the reversible means of mounting the covers44a,44bmay be simple shear screws passing firstly through the edge of the covers that are then preferably provided with peripheral metallic stiffeners, and secondly passing through the elements of the landing gear well that support these covers, in this case the lateral boxes68.

The removable covers44a,44bare preferably in the form of a honeycomb sandwich structure similar to that conventionally used for articulated fuselage covers closing off the lower part of the landing gear well.

InFIGS. 5a, 5b,6and7, the forward part of the aircraft1is shown with its removable covers removed. Each cover thus releases a manhole with a global rectangular area of the order of 1 m2, through which an operator can stand upright to perform fabrication/handling operations. It is a forward manhole76a, separated from a second manhole76bby the spar72.

Operators are shown in the lying down and upright positions inFIGS. 5ato7, in order to show the different access possibilities that can be made with these manholes76a,76b. In particular, the operator can stand upright through each of the passages, with his head just below the floor8.

According to another preferred embodiment shown inFIG. 8, the breaker strut36is mounted articulated on the lateral partitions66of the well22, in the same way as the extension jack84. Strut reactions are thus resisted satisfactory by the lateral boxes68.

In this preferred embodiment, as in the previous embodiment, the removable covers76a,76bare designed to resist only pressure, and do not resist any load originating directly from the forward landing gear30. Consequently they can be thin, for example about 100 mm thick.

Obviously, those skilled in the art could make various modifications to the invention that has just been described as non-limitative examples only.