Aircraft nose and nose landing gear bay structure

An aircraft nose structure includes a fuselage, a floor for a pressurized space and a nose landing gear bay arranged under the floor, on the opposite side to the space. The bay includes walls that form a pressure barrier, of which there are two lateral panels mechanically secured to the floor by load-reacting members, an upper panel adjacent to the floor and extending between the lateral panels, and a rear panel extending between the upper panel and the fuselage.

FIELD OF THE INVENTION

The invention relates to an aircraft nose structure provided with a nose landing gear bay, and to an aircraft provided with such a structure.

BACKGROUND OF THE INVENTION

An aircraft has a nose landing gear housed, when retracted, in a landing gear bay. This nose landing gear bay is usually located partially or completely under the floor of the aircraft flight deck.

In a conventional layout, the nose landing gear bay forms a box secured to the fuselage of the aircraft around an opening through which the landing gear can be lowered out of the bay in the landing configuration and retracted into the bay in the flight configuration. Moving doors close this opening in the flight configuration and open downwards when the landing gear is lowered.

The walls of such a nose landing gear bay are reinforced by a framework in order, firstly, to withstand the loads transmitted through the landing gear and, secondly, to form a pressure barrier. This is necessary because the walls of the nose landing gear bay are subjected, inside the bay, to the prevailing atmospheric pressure at the flight altitude and, outside the bay, to the prevailing pressure inside the aircraft in the pressurized region.

Document WO 2008/006956 discloses an aircraft nose landing gear bay of the type having an upper face partially forming a floor for a pressurized space of the aircraft.

BRIEF SUMMARY OF THE INVENTION

An aspect of the invention provides an aircraft nose structure that is optimized, notably from the mass standpoint, for a nose landing gear bay substantially of this type.

To this end, one embodiment of the invention is an aircraft nose structure comprising a fuselage, a floor for a pressurized space and a nose landing gear bay arranged under the floor, on the opposite side to the space, and comprising walls that form a pressure barrier, this structure being notable in that the pressure-barrier walls comprise at least two lateral panels mechanically secured to the floor by load-reacting members.

An advantage of this layout is that the lateral panels perform the dual function of acting as a pressure barrier and of transmitting to the floor the significant loadings applied to it by the shafts of the nose landing gear and struts that control it. These loadings are transmitted directly, with no intermediate components other than the load-reacting members, to the floor and, from there, to the wall of the fuselage via fuselage frames to which the floor is fixed.

According to one feature of the invention, the pressure-barrier walls comprise at least one upper panel adjacent to the floor and extending between the lateral panels. The upper panel does not absorb the significant loads applied by the landing gear and reacted by the floor: it is therefore designed solely to act as a pressure barrier and withstand impacts associated with the bursting of a landing gear tire.

According to another feature of the invention, the floor comprises crossmembers for reinforcing the upper panel. Thus, the floor crossmembers perform both the usual functions of stiffening the framework of the fuselage and of the floor itself, and those of transmitting to the fuselage loads originating from the nose landing gear and of reinforcing the pressure-barrier upper panel.

According to another feature of the invention, the floor comprises, between the crossmembers, load-reacting webs extending between the lateral panels and the fuselage. Like the crossmembers, these floor anti-shear webs contribute to reacting the loads transmitted by the landing gear.

In a preferred embodiment, the webs each comprise a flange mechanically secured to one of the lateral panels, thus providing a simple connection between these webs and the lateral panels.

According to another feature of the invention, the pressure-barrier walls comprise, between the lateral panels, a rear panel extending between the upper panel and the fuselage. This rear panel performs the same pressure-barrier function as the upper panel and, to a lesser extent than the latter, contributes to the stiffness of the bay. It can be designed accordingly.

According to another feature of the invention, the lateral panels comprise reinforcing uprights and the load-reacting members are components each respectively fixed to one of the reinforcing uprights and to one of the floor crossmembers. The means of transmitting loads from the lateral panels to the floor are thus particularly simple and easy to design.

In a preferred embodiment, the structure comprises crossmembers for reinforcing the rear panel running transversely between the ends of two of the reinforcing uprights. These crossmembers make it possible both to stiffen the bay in regions in which the lateral panels are not secured to the floor, and to reinforce the rear panel in its pressure barrier function.

According to another feature of the invention, the load-reacting members are angle brackets.

According to yet another feature of the invention, the upper panel comprises longitudinal rims for connection with the lateral panels, the longitudinal rims each being clamped between one of the lateral panels and the load-reacting members. Thus, the load-reacting members also contribute towards obtaining an effective pressure barrier where the lateral panels meet the upper panel.

Another embodiment of the invention includes an aircraft provided with a nose structure comprising one or more of the above features considered alone or in combination.

When this aircraft comprises a cabin provided with a cabin floor and a flight deck provided with the floor under which the nose landing gear bay is located, for preference, the flight deck floor is located at a lower level than the cabin floor. An advantage of the compactness of the nose landing gear bay layout afforded by the above-defined aircraft nose structure is that the floor of the flight deck can be lowered down to the level strictly necessary for housing the nose landing gear and, if appropriate, to below the level of the cabin floor of the aircraft (assumed to be in a horizontal position). One significant advantage of such a lowering of the flight deck floor is that it makes it possible, for roughly the same flight deck volume, to reduce the exterior surface area of the aircraft nose cone, and therefore the drag thereof.

With reference toFIGS. 1 to 3, an aircraft nose structure comprises a nose section1of a fuselage, of median axis XX′ in an orthonormal frame of reference of axes X, Y, Z, in which the axis Y-Y′ connects the wing tips (not depicted) of the aircraft. The fuselage nose section1comprises an exterior wall or skin2fixed to structural transverse fuselage frames3which are substantially parallel to one another and perpendicular to the XZ plane.

The fuselage nose section1comprises, at its front end, a nose4which contains electronic equipment (not depicted) such as a radar for example.

Behind the nose4, the fuselage nose section1is divided into two compartments by a floor5parallel to the XY plane.

In the compartment6situated above the floor5is an aircraft flight deck, whereas the compartment7situated under the floor5contains a landing gear bay8(for the sake of the clarity of the drawing, the landing gear has not been depicted).

The compartment6is extended rearwards by a compartment or cabin9situated above a floor10and intended to accommodate passengers or cargo.

The compartment7is extended rearwards, below the floor10, by a hold11intended to accommodate cargo, luggage, an avionics bay, etc.

The landing gear bay8is delimited at the top by an upper panel or roof12, at the front by a transverse bulkhead13, laterally by lateral panels14gand14d, and at the rear, firstly, by a rear panel15which extends obliquely downwards (along the axis ZZ′) between the rear edge of the upper panel12and a fuselage frame16and, secondly, by the lower part of the fuselage frame16which extends between the rear edge of the rear panel15and the wall2of the fuselage nose section1.

In the example depicted, the fuselage frame16marks the division between the flight deck6and the cabin or compartment9by means of a bulkhead (not depicted), although this dividing bulkhead could just as well be positioned in front of or behind the fuselage frame16.

The interior volume of an aircraft the nose section of which is depicted in the figures comprises:

a pressurized region notably comprising the flight deck (compartment6), the compartment9that accommodates the passengers or cargo, the hold11and lateral volumes32situated on either side of the landing gear bay lateral panels23, and

a non-pressurized zone subjected to the prevailing atmospheric pressure at the altitude at which the aircraft is flying, and comprising the interior volumes of the nose4of the aircraft and of the landing gear bay8.

In the fuselage nose section1, the division between the pressurized and unpressurized zones is embodied by a certain number of bulkheads or panels designed to form a pressure barrier and which comprise:

an upper transverse bulkhead17, preferably planar, which, above the floor5, separates the flight deck6or compartment, which is pressurized, from the space inside the nose4, which is not pressurized,

the lower transverse bulkhead13, preferably planar, which not only closes the bay8in its front part, but connects to the bulkhead17and to the fuselage nose section1to achieve a pressuretight division between the space inside the nose4and that of the compartment7, on either side of the lateral panels14dand14gof the bay8;

the upper panel or roof12of the bay8, which is planar and positioned under and against the floor5; this upper panel12is connected in a pressuretight manner, firstly laterally to the lateral panels14dand14gand secondly at the front to the transverse bulkheads13and17;

the lateral panels14dand14gof the bay8which are planar and have a substantially polygonal overall shape; these lateral panels14dand14gare each connected in a pressuretight manner:to the transverse bulkhead13along a front edge;to the upper panel12along an upper edge,to the rear panel15along an inclined first rear edge;to the lower part of the transverse fuselage frame16along a second rear edge which is located in the plane of this fuselage frame16, andto a reinforcing fuselage frame or box section18which delimits the opening through which the landing gear passes and to which the transverse frames3of the fuselage2are connected in the region of the bay8; and

the rear panel15of the bay which is connected in a pressuretight manner to the upper panel12, to the lateral panels14dand14galong their first rear edge, and to the lower part of the fuselage frame16.

These panels and bulkheads are joined together by joining elements that are either added on or form part of one or other of the connected panels as described hereinafter with regard to the connection between the upper panel12and the lateral panels14d,14g. The upper17and lower13transverse bulkheads and the upper12, lateral14d,14g, and rear15panels are preferably made of a metallic or composite material.

As a result, the space inside the fuselage2which surrounds the bay8to the rear of the bulkheads13and17forms part of the pressurized zone of the aircraft and the bay8, the interior volume of which is at atmospheric pressure, constitutes an enclave within this pressurized zone.

Significant loadings are transmitted by the landing gear, particularly during landing phases, to the lateral panels14dand14gvia bearings21carrying the shafts about which the legs (not depicted) supporting the wheels of the landing gear are articulated and bearings20carrying the shafts about which the struts (not depicted) which control the lowering and retraction of the landing gear (not depicted) are articulated. Further, the lateral panels14dand14gare also subjected to the loadings resulting from the pressurization.

In order to be able to absorb these loads, the lateral panels14dand14gare reinforced on the outside of the bay8by uprights23made of a metallic or composite material which are fixed to them and which run parallel to one another, for example along the axis ZZ′ in instances in which the lateral panels14dand14gare perpendicular to the floor5. The uprights23preferably have a T-shaped, C-shaped, I-shaped, or some other shaped profile, the main flange of which is fixed to the panels14dand14gby fixing means (not depicted) or incorporated directly into the panels14dand14g.

In line with the upper panel12, the uprights23do not extend over the full height of the lateral panels14dand14g. Their upper end23astops short of the upper edge of the lateral panels14dand14gand thus leaves a flat strip against which the upper panel12is fixed as indicated hereinbelow. At their lower end, the uprights23are fixed to the reinforcing frame or box section18or to one of the transverse fuselage frames3, depending on whether or not they are in line with the opening of the bay8.

The floor5in the conventional way comprises crossmembers24made of a metallic or composite material, of IPN or UPN profile which extend transversely on either side of the fuselage2and are fixed at each of their respective ends to a transverse fuselage frame3. Because they are anchored to the transverse fuselage frames3, the crossmembers24contribute in the way known per se to the stiffness of the aircraft fuselage nose section1.

Fixed between the crossmembers24are shear webs which, in the region of the upper panel12, extend between the adjacent edge of the upper panel12and the wall of the fuselage2.

As depicted in greater detail inFIG. 4, the shear webs25comprise, on the side of the lateral panels14dand14g, a flange26at a right angle.

Finally, the floor5comprises, in the region covering the upper panel12, spars27made of a metallic or composite material and which, with the crossmembers24, contribute to reinforcing the upper panel12subjected to the loadings of pressurization. The spars (which have not been depicted in their entirety)27extend from the transverse bulkhead17to the fuselage frame16. They stabilize the floor and provide retention for the panel17when the latter is subjected to the pressurization. Other spars27(not depicted in the figures) extend on each side of the landing gear bay8.

The upper panel12is fixed by its upper face to the crossmembers24by fixing means (not depicted) which are conventionally used in pressuretight zones. The crossmembers have three functions: they react the fuselage1pressurization loadings, they stabilize and reinforce the landing gear bay roof12, and they support the flight deck6floor that is walked on.

In order to connect the upper panel and the lateral panels in a pressuretight manner, the upper panel12has lateral rims at right angles28which are fixed by conventional fixing means against the flat strip of the exterior face of the lateral panels14dand14gwhich extends between their upper edge and the upper ends of the uprights23. As an alternative, the upper panel12may be flat and the longitudinal rims may consist of added-on joining elements of the angle bracket type or, alternatively, the lateral panels may comprise lateral rims for fixing them to the flat upper panel12.

These lateral rims28and the flanges26of the shear webs25are kept clamped against the exterior faces of the lateral panels14dand14gby bracket-shaped load-reacting components29made of a metallic or composite material. The components29are each fixed by one29aof their flanges to the flange of one of the uprights23and by the other29bof their flanges to the flange of one of the crossmembers24by conventional fixing means (not depicted). For that purpose, the webs25have slots (not visible in the drawing) through which the bracket-shaped components29can pass.

Finally, the rear panel15of the bay8is likewise reinforced by crossmembers30made of a metallic or composite material which are specific to the bay8. The crossmembers30are parallel to those of the floor5(and to the XY plane) and fixed by conventional fixing means (not depicted) at their ends to the respective ends of two uprights23. The crossmembers30and the corresponding uprights23thus form portal frames which are anchored to the fuselage frame18and flank the lateral panels14dand14gand the rear panel15.

Thanks to the above-described aircraft nose section structure, all the loads applied by the landing gear to the lateral panels14dand14gare transmitted to the floor5and, from there, are reacted by the wall2of the aircraft fuselage. The above-described aircraft nose section structure optimizes mass because this transmission of load from the landing gear is obtained using a minimum number of components and because just one subassembly, the floor, reacts the loads transmitted by the landing gear and those resulting from the pressurization.

Finally, because of the compactness achieved by imbricating the landing gear bay8with the floor5, the latter can be lowered (along the axis ZZ′) by comparison with the position that it occupies in a conventional configuration in which the flight deck floor and the nose landing gear bay are independent. AsFIG. 1shows, the floor5can be situated below the level of the floor10of the cabin or compartment9, unlike in the state of the art of aircraft of the same type in which the flight deck and the cabin or cargo or passenger compartment are at the same level (rather than at different levels as may be the case for very large transport aircraft).

As a result of this lowering of the floor5, the surface area of the fuselage nose section1of the aircraft can, for substantially the same flight deck volume, be reduced as shown inFIG. 1: the outline31drawn in chain line shows what the exterior surface of the fuselage nose section1would be if the floor5extended in the continuation of the cabin floor10.

This reduction in the surface area of the fuselage nose section1results in a reduction in drag and, therefore, in aircraft fuel consumption. The reduction in exterior surface area also leads to a reduction in mass.