Patent Description:
Although the invention may be useful in various applications in the field of aircraft or spacecraft design and production, the invention and the underlying problem will be explained in the following in greater detail and exemplary manner with regard to a pressure bulkhead interface as part of a fuselage of an airplane, in particular near the tail of such a fuselage.

In passenger aeroplanes, a large portion of the fuselage commonly accommodates a pressurized passenger cabin. It is known to terminate the pressurized portion of the fuselage at its rearward end by a pressure bulkhead, which separates the pressurized portion of the fuselage from a rear fuselage portion that is unpressurized.

<CIT> and <CIT> discloses aircraft structures with pressure bulkheads.

<CIT> and <CIT>, for instance, describe a pressure fuselage of an aircraft or spacecraft, assembled from several fuselage sections, and describe an arc-shaped frame profile having a Y-shaped cross section for attaching a pressure calotte on the inside of an associated fuselage section.

In <CIT> and <CIT>, a fuselage structure of an aircraft or spacecraft is described, wherein a plurality of tension struts each connect a pressure calotte to a skin portion.

Moreover, <CIT> describes a pressure bulkhead located at a junction of fuselage compartments, wherein fittings on opposite sides of the pressure bulkhead, a wall of an outer belt bridging the junction between skins of the fuselage compartments and having an outer contour close to the shape of these skins at the junction, a wall of the pressure bulkhead, and a backup tape are connected by a bolted connection.

In conventional approaches to implementing an orbital junction at the rear pressure bulkhead interface, loads between adjacent fuselage sections are transmitted mainly as shear loads e.g. using fasteners such as rivets. However, such conventional designs usually entail a comparatively complex, time-consuming assembly process, involving a significant number of separate parts that must be individually assembled. Accessibility during assembly may be complex, which can contribute to a lengthy and expensive process.

Against this background, it would be desirable to provide a reliable structural junction in the region where a pressure bulkhead, particularly a rear pressure bulkhead, is to be coupled to a fuselage skin and/or a stiffening structure thereof, and at the same time to make it possible to facilitate the assembly of fuselage sections in the part of the fuselage concerned and to reduce assembly lead time. Further, it would be preferable to be able to perform significant pre-assembly of fuselage sections, to be placed adjacent the pressure bulkhead interface, in a simple manner.

In view of this, the problem to be solved by the invention is to provide a structural junction that can be assembled in improved manner and thereby to reduce assembly lead time. Further, a correspondingly improved method of forming a structural junction, and a correspondingly improved aircraft or spacecraft, are to be proposed.

According to the invention, this problem is solved by a fuselage as claimed in claim <NUM> and/or by an aircraft or spacecraft having the features of claim <NUM> and/or by a method of forming a structural junction in an aircraft or spacecraft fuselage having the features of claim <NUM>.

An idea underlying the invention is that using the first and second fittings and tension bolts, a component integrally overlapping the joint between fuselage sections, forward and aft of the pressure bulkhead, connecting these fuselage sections based on a shear attachment principle, e.g. by riveting, at the level of the fuselage skin in both skin portions and transmitting tensile loads along the skin and across the joint, can be avoided.

For instance, therefore, pre-assembly of each of the first and second sections is possible even when the fuselage tapers, such as towards the tail of an airplane.

Moreover, by providing a first and second fitting and transmitting tensile loads using the tension bolts, geometrically overly complex components can be avoided, and the fittings can be manufactured with reasonable effort.

Furthermore, as the inner flange is spaced apart from the fuselage skin, an offset between the pressure bulkhead skin and the fuselage skin is provided, which may be advantageous. System lines such as cables, tubes, or the like can be led from a pressurized to an unpressurized fuselage section, or vice versa, without necessarily penetrating the pressure bulkhead skin, for example.

The structural junction proposed by the invention thus makes it possible to pre-assemble both first and second fuselage sections before joining them. Therefore, the assembly lead time can be reduced. Also, less parts have to be assembled at least during joining the sections, the access for workers during the assembly process is significantly improved, and the required operations can be performed in a more ergonomic manner, which further reduces time and effort required for assembly.

In the present invention, the tension bolts can transfer at least tensile loads, which should be understood to encompass in particular implementations in which the tension bolts transfer substantially only tension loads as well as implementations in which the tension bolts transfer both shear and tension loads, for example.

Advantageous improvements and developments of the invention are contained in the dependent claims as well as in the description referring to the drawings.

In particular, an outer surface of the first outer flange may abut against an inner surface of the fuselage skin in the first section, and an outer surface of the second outer flange may abut against an inner surface of the fuselage skin in the second section. For example, the first outer flange may be attached to the portion of the fuselage skin in the first section using fasteners, such as e.g. rivets, and/or the second outer flange may be attached to the portion of the fuselage skin in the second section using fasteners, such as e.g. rivets. In this manner, the outer flanges can be attached to the fuselage skin in the associated fuselage section in a reliable manner and so as to transmit shear loads from the outer flange to the associated portion of the fuselage skin.

In a development, the inner flange of the first fitting obliquely extends with respect to the first web to which it is connected. In this manner, the pressure bulkhead skin formed as, for example, a pressure calotte can be conveniently and reliably attached to the inner flange.

In particular, the pressure bulkhead skin may be arranged in such a manner that an edge portion of the pressure bulkhead skin overlaps with the inner flange. Further preferably, the pressure bulkhead skin may be attached to the inner flange using fasteners, such as for example rivets. In this way, a reliable attachment of the pressure bulkhead skin to the inner flange is obtained.

According to a development, preferably, the first fitting is integrally formed with the inner flange thereof. This may help to reduce weight and simplifies pre-assembly of the first fuselage section.

In a development, the first web, the first outer flange and the inner flange of the first fitting are formed integrally with each other. In a further development, the second web and the second outer flange of the second fitting are formed integrally with each other. In this way, structural weight can be limited or reduced, and furthermore, these developments may contribute to a space-saving design of the first and second fitting, respectively.

In particular, the first web of the first fitting and the second web of the second fitting extend substantially parallel to each other and/or contact each other along a first main surface of the first web and a second main surface of the second web. In this way, the fittings can be reliably connected by the plurality of tension bolts.

In accordance with an improvement, the tension bolts each extend through the first web and through the second web in such a manner as to join the first and second webs, wherein in a state in which the first and second fittings are connected at least by the tension bolts, the first and second webs abut against each other and the inner flange of the first fitting preferably extends over an inner end of the second web of the second fitting. Accordingly, the fittings can be reliably connected, while access to the location where the connection via the tension bolts is to be established is facilitated. In particular, with the inner flange preferably extending over the inner end of the second web, access to the location where the pressure bulkhead skin is to be attached to the first fitting can be facilitated during pre-assembly of the first fuselage section.

In particular, a location at which the fuselage skin portions of the first and second fuselage sections adjoin each other substantially corresponds to a location where the first and second webs abut against each other. In this way, pre-assembly of the fuselage sections is significantly facilitated also if the fuselage tapers, for example following a curved profile, in the region of the joint between the fuselage sections. A slight gap may exist between adjacent edges of the skin portions.

In particular, the first web and the first outer flange may form legs of an L-shaped section of the first fitting and/or the second web and second outer flange may form legs of an L-shaped profile of the second fitting.

Further, in accordance with an improvement, the first fitting comprises a plurality of first ribs arranged transverse to the first web and the first outer flange and/or the second fitting comprises a plurality of second ribs arranged transverse to the second web and the second outer flange. In accordance with this improvement, the first and/or second ribs are arranged along a circumferential direction of the fuselage, in the region where the first and second fuselage sections are joined, so as to form pairs of first and/or second ribs. In this manner, further support between the web and outer flange may be provided in each case, the connection of the first web and first outer flange and/or of the second web and second outer flange can be additionally stiffened and loads may be transmitted more effectively between the webs and outer flanges.

Preferably, the first ribs and the second ribs are formed at corresponding locations along the circumferential direction. Further preferably, a tension bolt is arranged in a region of the first and second webs between the ribs of one of the pairs. Thus, the ribs can contribute in a particularly effective manner to support the loads transmitted by the tension bolts.

In a development, at least the first fuselage section further comprises a plurality of stringers arranged spaced from each other along the circumferential direction of the fuselage, a longitudinal axis of each of the stringers being oriented substantially transverse to the first fitting, wherein a position of each of the stringers along the circumferential direction substantially corresponds to a circumferential position of one of the pairs of ribs. Hence, loads can be supported even more efficiently by the stiffening structure stiffening the fuselage skin.

According to a development, the pairs of first ribs and the pairs of second ribs each are spaced from one another in the circumferential direction, whereby intermediate regions of the first and second webs between consecutive pairs of ribs are defined, wherein the first and second webs are additionally joined in the intermediate regions in a manner essentially transmitting shear between the first and second webs. Hence, additional shear load can be transmitted between the first and second fittings.

In a development, the tension bolts are configured to connect the first and second fittings using a threaded connection. Such a connection is well adapted to the transmission of tensile loads. With such a connection, assembly can be performed in expedient manner.

In particular, the first and second fittings are manufactured as separate parts which are, during assembly of the fuselage, connected to each other at least by the tension bolts. In particular, the first fitting and the second fitting are parts which are configured to be structurally connected to each other at least by the tension bolts, wherein the first and second fittings and the tension bolts are configured in a manner enabling the tension bolts to transmit tensile loads or to transmit tensile loads and shear loads.

In a further development, the first fitting and/or the second fitting is/are each formed elongate and in particular is/are arranged in such a manner as to substantially extend along a circumferential direction of the fuselage.

Moreover, in an improvement, the first fuselage section comprises a frame arranged next to the first fitting and in such a manner as to extend substantially along a circumferential direction of the fuselage, wherein the frame is arranged spaced from the first fitting by a distance and is connected to the first fitting at a plurality of locations along the circumferential direction, in particular by a plurality of cleats bridging the distance between the frame and the first fitting. Connecting the first fitting with the frame in this manner contributes to preventing the frame from deforming in undesirable manner.

In a further development the first fitting can be formed integrally with the frame. In particular, in this development, the cleats can be formed integrally with the frame and the first fitting. In this way, the weight of the junction can be reduced further.

In another development, the frame, the first fitting and the cleats can be formed as separate parts that are joined during assembly of the first fuselage section. In this manner, the production of the frame, the first fitting and the cleats can facilitated.

In still another development, the cleats can be formed integrally with either the frame or the first fitting. Thereby, some reduction in weight can be achieved along with moderate complexity of the components to be produced.

In another development, the cleats each connect a web of the frame to an assigned one of the ribs of the first fitting. In this way, the shape of the cleats can be kept relatively simple, while the connections with both the web and rib can be established in expedient manner. In particular, cleats each having an L-type shape may be used.

In particular, the improvements, developments and enhancements of the invention described above may be applied in analogous manner to each of the structural junction, the aircraft or spacecraft, and the method proposed herein.

The invention will be explained in the following with reference to the schematic figures of the drawings which illustrate embodiments of the invention.

The enclosed drawings are intended to illustrate embodiments of the invention so that the invention may be further understood. The drawings, in conjunction with the description, are intended to explain principles and concepts of the invention. Other embodiments and many of the advantages described may be inferred from the drawings. Elements of the drawings are not necessarily drawn to scale.

Elements, features and components which are identical or which have the same function or effect have been labeled in the drawings using the same reference signs, except where explicitely stated otherwise.

<FIG> illustrate an aircraft in the form of a passenger aeroplane <NUM>, comprising a fuselage <NUM> having a nose <NUM> and a tail <NUM>, wings <NUM> as well as a vertical stabilizer <NUM> and horizontal stabilizer <NUM> in the region of the tail <NUM>. The fuselage <NUM> is constructed, for example, according to a semi-monocoque design, generally comprising an outer skin <NUM> reinforced on the inner side thereof by a reinforcing structure including stringers, which are essentially longitudinally arranged, as well as frames essentially extending transverse to the stringers. The fuselage <NUM> is divided into several barrel-shaped sections, which are assembled to form the entire fuselage <NUM>. A fuselage section may be formed from several shells.

The aircraft <NUM> comprises a passenger cabin, not shown in detail in the figures, throughout a large part of the fuselage <NUM>. The passenger cabin is designed to accommodate the passengers. In order to provide the passengers with a suitable, safe and comfortable environment for travel at great height above ground, a large part of the fuselage <NUM> can be pressurized. The pressurized fuselage portion is closed, near the tail <NUM>, by a rear pressure bulkhead <NUM>, displayed in <FIG>. The rear pressure bulkhead <NUM> comprises a pressure bulkhead skin <NUM> or membrane, which may be shaped in the manner of a cap or calotte.

<FIG> show first and second fuselage sections 2a and 2b near the tail <NUM>. The forward section 2a and the rearward section 2b are joined at an orbital joint or orbital structural junction <NUM> situated substantially at the position of the rear pressure bulkhead <NUM>. The first fuselage section 2a, forward of the bulkhead <NUM>, is thus a pressurizable section, while the second fuselage section 2b, rearward of the bulkhead <NUM>, is unpressurized. Other sections in the direction towards the nose <NUM> of the airplane <NUM> are not shown in detail in <FIG>.

In the embodiment displayed in the figures, the first and second fuselage sections 2a, 2b can each be pre-assembled and then joined at the position indicated by reference numeral <NUM>, which designates the location of the joint. Thereby, it is in particular made possible to achieve at reduction in assembly lead time.

The orbital structural junction <NUM> according to an embodiment will be described in the following in greater detail in particular with reference to <FIG> and <FIG>.

<FIG> shows a perspective view of a part of the junction <NUM>, in a schematic manner. In particular in a direction U along the circumference of the fuselage <NUM>, only a portion of the junction <NUM> is shown. Further, along the longitudinal direction X of the completed fuselage <NUM>, for the sake of clarity, only adjacent portions of the first and second sections 2a and 2b are displayed, while the sections 2a, 2b may typically be longer than the parts displayed in the figures.

Also, it should be understood that - while <FIG>, <FIG> show the junction <NUM> in a schematic manner in the form of a development in the circumferential direction U of the fuselage <NUM> at the location <NUM> of the junction <NUM> - the sections 2a and 2b have a generally round cross-section and are joined at the location <NUM> along a closed curve.

The first section 2a comprises a outer skin portion 17a, while the second section 2b comprises an outer skin portion 17b. The skin portions 17a, 17b form, in cooperation with each other and with further skin portions in other sections, the outer skin <NUM> of the fuselage <NUM> after assembly of the latter.

In the orbital structural junction <NUM> of the embodiment, a first fitting <NUM> is attached to the fuselage skin portion 17a in the first fuselage section 2a, and a second fitting <NUM> is attached to the fuselage skin portion 17b in the second fuselage section 2b. Adjacent, opposing edges 12a, 12b of the skin portions 17a and 17b, respectively, are shown in <FIG> in greater detail. The edges 12a and 12b each form adjacent edges of the fuselage sections 2a and 2b, respectively, or parts thereof, and in the region of these edges of the sections 2a, 2b, the sections 2a and 2b are joined at the location <NUM>.

The first fitting <NUM> is attached to the skin portion 17a close to the edge 12a of the portion 17a, while the second fitting <NUM> is attached to the skin portion 17b close to the edge 12b of the portion 17b. Fitting <NUM> may protrude beyond the edge 12a by a small distance, and fitting <NUM> may protrude beyond the edge 12b by a small distance, thus forming a small gap between the edges 12a, 12b in the assembled state as shown in <FIG>.

Each of the first and second fittings <NUM>, <NUM> substantially extends along the adjacent edges 12a, 12b in the circumferential direction U of the fuselage <NUM> and each are formed according to a generally elongate shape.

The first fitting <NUM> comprises a first outer flange <NUM>. An outer surface of the outer flange <NUM> abuts against an inner surface of the skin portion 17a. Via the first outer flange <NUM>, the first fitting <NUM> is joined to the skin portion 17a, for example using a plurality of fasteners, such as rivets. Moreover, the first fitting <NUM> comprises a first web <NUM>, arranged substantially transverse to the first outer flange <NUM>. In the embodiment shown, the first web <NUM> extends substantially perpendiculary to the first outer flange <NUM>. In cooperation, the web <NUM> and outer flange <NUM> form an L-shape in the cross-section of the first fitting <NUM>, the web <NUM> and flange <NUM> forming legs of the L-shape. In variants, the angle between the first web <NUM> and first outer flange <NUM> may differ from <NUM> degrees.

In addition, the first fitting <NUM> comprises an inner flange <NUM>. The first web <NUM> connects the inner flange <NUM> and the first outer flange <NUM>. Furthermore, the inner flange <NUM> and the first outer flange <NUM> extend from opposing ends of the first web <NUM> into different directions, with the inner flange <NUM> obliquely extending with respect to the first web <NUM>.

The first outer flange <NUM>, the first web <NUM> and the inner flange <NUM> are formed integrally with each other. For example, the first fitting <NUM> may be formed by machining, e.g. by milling, whereby the flanges <NUM>, <NUM> and the web <NUM> may be formed as integral portions of the first fitting <NUM>.

The second fitting <NUM> comprises a second outer flange <NUM>, an outer surface of which abuts against an inner surface of the skin portion 17b. Via the second outer flange <NUM>, the second fitting <NUM> is joined to the skin portion 17b, for example using a plurality of fasteners, such as rivets. The second fitting <NUM> comprises a second web <NUM>, arranged transverse to the second outer flange <NUM> and connected to the second outer flange <NUM>. In the embodiment displayed in the figures, the second web <NUM> extends substantially perpendicularly to the second outer flange <NUM>. In cooperation, the web <NUM> and outer flange <NUM> form an L-shape in the cross-section of the second fitting <NUM>, the web <NUM> and flange <NUM> forming legs of the L-shape. In variants, the angle between the second web <NUM> and the second outer flange <NUM> may differ from <NUM> degrees.

<FIG>, for example, shows that in the assembled state, the L-shapes of the first and second fittings <NUM>, <NUM> are arranged in a substantially symmetric manner with respect to the surface defining, in <FIG>, the location <NUM> where both sections 2a, 2b are joined.

In a manner analogous to the first fitting <NUM>, the second outer flange <NUM> and the second web <NUM> are formed integrally with each other in the second fitting <NUM>. For example, the second fitting <NUM> may be formed by machining, e.g. by milling, whereby the flange <NUM> and the web <NUM> may be formed as integral portions of the second fitting <NUM>.

After assembly of the fuselage <NUM>, the outer fuselage skin <NUM> encloses an inner space <NUM> of the fuselage <NUM>. In the junction <NUM>, the inner flange <NUM> of the first fitting <NUM> is spaced apart from the fuselage skin <NUM> towards the inner space <NUM> of the fuselage <NUM> by a distance substantially defined by the height of the first web <NUM> with respect to the outer surface of the first outer flange <NUM>, see for example <FIG> and <FIG>.

The pressure bulkhead skin <NUM> is connected, in a circumferential region along its outer edge, to the inner flange <NUM>. <FIG>, <FIG> in particular show that an edge portion of the pressure bulkhead skin <NUM> overlaps with the inner flange <NUM> and is attached thereto, for example using fasteners such as rivets, not shown in the figures. As the inner flange <NUM> is obliquely inclined relative to the first web <NUM>, and hence in particular is also inclined with respect to the fuselage skin <NUM>, the calotte-shaped pressure bulkhead skin <NUM> can be conveniently and reliably connected to the inner flange <NUM>.

<FIG> and <FIG>, for example, show that in the embodiment, the first fitting <NUM> and the second fitting <NUM> abut against each other at the location <NUM> of the orbital joint. In the assembled state displayed, the first web <NUM> and the second web <NUM> extend parallel to each other. A first main surface <NUM> of the first web <NUM> is turned towards and contacts an opposing second main surface <NUM> of the second web <NUM>. As seen in <FIG>, in the embodiment, the location of the surface contact, where the webs <NUM>, <NUM> abut along their surfaces <NUM>, <NUM>, coincides with the location <NUM> of the joint and extends substantially through the center of a small gap formed between the edges 12a, 12b of the fuselage skin portions 17a, 17b.

In the assembled junction <NUM>, see <FIG>, <FIG> in particular, the inner flange <NUM>, which forms an integral part of the first fitting <NUM>, extends over an inner end <NUM> of the second web <NUM> of the second fitting <NUM>, and hence into the second fuselage section 2b. The inner end <NUM> is an end of the second web <NUM> that is distant from the second outer flange <NUM> to which the second web <NUM> is connected. Accordingly, in the junction <NUM>, the first outer flange <NUM> is arranged on the inner side of the fuselage skin portion 17a of the first section 2a, but the inner flange <NUM> extends into the second section 2b at a distance from the fuselage skin portion 17b, and hence not at the level of the fuselage skin <NUM>. In this way, pre-assembled sections 2a, 2b can be joined in a simple manner.

The first and second fittings <NUM>, <NUM> are manufactured as separate parts. During the process of assembly of the fuselage <NUM>, the first and second fitting <NUM>, <NUM> are connected at least by a plurality of tension bolts <NUM>, schematically shown in <FIG> and <FIG>. The tension bolts <NUM> each extend through the first web <NUM> and the second web <NUM> so as to join the webs <NUM>, <NUM> and thereby the fittings <NUM>, <NUM>.

The tension bolts <NUM> in particular may be configured as threaded bolts. For example, the tension bolts <NUM> each may comprise a head and a threaded shaft, and a nut may be provided to securely connect the first and second fittings <NUM>, <NUM> using a threaded connection. The head may directly or indirectly abut on one of the webs <NUM>, <NUM>, while the nut may directly or indirectly abut on the other one of the webs <NUM>, <NUM>.

After assembly, in the state shown in <FIG>, <FIG> and <FIG>, the tension bolts <NUM> transfer at least tensile loads acting at the junction <NUM> between the fittings <NUM>, <NUM>. Preferably, the tensile loads supported and transferred by the plurality of tension bolts <NUM>, e.g. via the respective head, shaft and nut thereof, may correspond to substantially the entire tensile load acting between the sections 2a, 2b across the junction <NUM> and across the edges 12a, 12b. The direction of the tensile loads transferred by the tension bolts <NUM> substantially corresponds to the longitudinal direction X of the fuselage <NUM>.

The tension bolts <NUM> each for example may pass through an assigned through-hole in both the first and second web <NUM>, <NUM>. The through-hole may in particular be formed by drilling through both webs <NUM> and <NUM>.

In variants of the embodiment, the tension bolt <NUM> and the assigned through-hole through which it passes may be configured with sufficient play, in such a manner that the tension bolts <NUM> substantially transmit tensile loads, or the tension bolt <NUM> and the through-hole may alternatively be configured, for example, for a snug fit or interference fit, whereby the tension bolts <NUM> also can transmit shear loads parallel to the webs <NUM>, <NUM> between the first and second fittings <NUM>, <NUM>, in addition to the tensile loads acting transverse to the webs <NUM> and <NUM>. Such shear loads may for example result from torsion loads coming from the rear fuselage. If transmission of shear loads is desired via the tension bolts <NUM>, these may be provided with a shaft having an unthreaded portion.

In a variant, in case access to an interior of one of the sections 2a, 2b, or to a portion thereof, is limited or difficult in the step of joining the sections 2a, 2b, one of the webs <NUM>, <NUM> that is easily accessible can be provided with a through hole, and the other one of the webs <NUM>, <NUM> may be provided with a recess adapted to receive a barrel nut, for example. The recess in this variant in particular is configured such that into a transverse threaded hole of the barrel nut, a threaded shaft portion of the tension bolt <NUM>, distal from the head thereof, can be screwed.

The first fitting <NUM> comprises a plurality of first ribs <NUM>, <NUM> which extend transversely, in particular substantially perpendicularly, to the first outer flange <NUM> and the first web <NUM> and are integrally connected to the flange <NUM> and the web <NUM>. The first ribs <NUM>, <NUM> are arranged in pairs <NUM> each comprising one rib <NUM> and one rib <NUM>. In particular, see <FIG>, the ribs <NUM>, <NUM> may alternate along the circumferential direction U of the fuselage <NUM> at the location <NUM>.

The first ribs <NUM>, <NUM> are spaced from each other along the circumferential direction U, the spacing being greater between consecutive pairs <NUM> than between the ribs <NUM> and <NUM> of the same pair <NUM>.

Each rib <NUM> approximately has a shape of a triangular plate. Each rib <NUM> has a shape that comprises, in additional to a triangular base shape analogous to that of the rib <NUM>, a tab <NUM> that extends the plate-like shape of the rib <NUM> on the side thereof directed toward an interior of the first fuselage section 2a. This is illustrated in <FIG> by a dash-dotted line. The function of the tab <NUM> is explained below.

At locations along the circumferential direction U which correspond to the positions of the first ribs <NUM> and <NUM>, the second fitting <NUM> comprises a plurality of second ribs <NUM>, arranged in pairs <NUM>. In a manner substantially analogous to the first ribs <NUM>, <NUM>, the second ribs <NUM> extend transverse, in particular perpendicular, to the second web <NUM> and the second outer flange <NUM>. The spacing of the second ribs <NUM> in the circumferential direction U corresponds to the spacing of the first ribs <NUM>, <NUM>. The second ribs <NUM> are integrally connected to the second web <NUM> and the second outer flange <NUM>.

Different from the ribs <NUM>, <NUM>, the second ribs <NUM> of the second fitting <NUM> are each shaped in the same manner, and each have a triangular plate-type shape similar to that of the first ribs <NUM>.

The ribs <NUM>, <NUM>, <NUM> provide support and stiffening of the fittings <NUM>, <NUM> at the junction <NUM>, where substantial loads are to be transmitted. Using the ribs <NUM>, <NUM>, <NUM>, it becomes possible to transmit loads acting through the skin portions 17a, 17b more effectively from the outer flanges <NUM>, <NUM> to the webs <NUM>, <NUM> abutting on each other.

The tension bolts <NUM> are each arranged in a region <NUM> of the web <NUM> between the ribs <NUM>, <NUM> of a pair <NUM> and in a corresponding region <NUM> of the web <NUM> between the ribs <NUM> of a pair <NUM>. The pairs <NUM>, <NUM> of ribs <NUM>, <NUM>, <NUM> help to effectively and evenly support the loads transmitted at the interface <NUM>, in particular the tensile loads supported by the bolts <NUM>.

<FIG> and <FIG> show that at least the first fuselage section 2a comprises a plurality of stringers <NUM> arranged spaced from each other along the circumferential direction U. A longitudinal axis <NUM> of each of the stringers <NUM> is oriented approximately transverse to the first web <NUM>. A position of each stringer <NUM> along the circumferential direction U substantially corresponds to a circumferential position of one of the pairs <NUM>, <NUM> of ribs. The position of the pairs <NUM>, <NUM> is understood, in this embodiment, as being the position at approximately half the spacing between the ribs <NUM>, <NUM> or <NUM> of the pair <NUM> or <NUM>, respectively. The tension bolts <NUM> each are being arranged centrally between the ribs <NUM>, <NUM> and <NUM>, <NUM> of the corresponding pairs <NUM> and <NUM>, respectively. The position of a web of the stringer <NUM> also may approximately correspond to the center between the ribs of each pair <NUM>, <NUM>, seen in the circumferential direction U. The arrangement of the stringers <NUM> in the embodiment helps to transmit loads exchanged at the interface of the first and second webs <NUM>, <NUM>, in particular through the tension bolts <NUM>, even more efficiently to the skin <NUM>.

Intermediate regions <NUM> of the first webs <NUM> between consecutive pairs <NUM>, and intermediate regions <NUM> of the second webs <NUM> between consecutive pairs <NUM>, are located at corresponding positions along the circumferential direction U. For transmitting shear loads in the plane defined by the main surfaces <NUM>, <NUM> of the webs <NUM> and <NUM>, the first and second fittings <NUM>, <NUM> can additionally be connected in the intermediate regions <NUM>, <NUM>, in particular by fasteners extending through the first and second webs <NUM>, <NUM>, for example by rivets, or by shear bolts, for instance. Areas where the webs <NUM>, <NUM> could be riveted within the intermediate regions <NUM>, <NUM> are indicated in exemplary manner by dashed lines in <FIG> for a region <NUM> and in <FIG> for two consecutive regions <NUM>.

A short distance ahead of the first fitting <NUM>, the first fuselage section 2a comprises a frame <NUM> extending transverse to the stringers <NUM> and substantially in the circumferential direction U. In this embodiment, the frame <NUM> is formed with an elongated, profiled component having a substantially Z-shaped cross-section. The profiled component of the frame <NUM> is connected to the stringers <NUM> and to the skin portion 17a by a plurality of cleats <NUM>. Each cleat <NUM> comprises a surface adapted for attachment to the frame <NUM>, a further surface adapted for attachment to the skin portion 17a, and a further surface adapted for attachment to one of the stringers <NUM>, see <FIG> and <FIG>.

Moreover, the frame <NUM> is further connected to the first fitting <NUM> at a plurality of locations along the circumferential direction U by a plurality of cleats <NUM>. Each cleat <NUM> connects a web of the frame <NUM> to an assigned one of the ribs <NUM> of the first fitting <NUM>. In order to attach the cleat <NUM> to the rib <NUM>, a first leg of the cleat <NUM> is connected to the tab <NUM>, for example by fasteners, e.g. rivets. A second leg of the cleat <NUM> is connected to the web of the frame <NUM>. The first and second legs of the cleat <NUM> in cooperation form an L-type shape, see in particular <FIG>.

The cleat <NUM> bridges the distance between the frame <NUM> and the first fitting <NUM>, the latter being positioned at the edge 12a of the skin portion 17a as explained above. The connection by the cleats <NUM> helps to stabilize the frame <NUM> against undesirable deformation under load.

In addition to the frame <NUM>, the first fuselage section 2a may be provided with a number of further frames, running transverse to the stringers <NUM> and are not shown in the figures.

In the embodiment illustrated in the drawings, the first fitting <NUM>, the frame <NUM>, the cleats <NUM> and the cleats <NUM> are formed as separate, individual parts which are connected to each other in the manner described above during assembly of the fuselage section 2a, e.g. by riveting.

In order to further reduce the weight of the junction <NUM> and reduce the amount of work required for connecting the individual components, some or all of the fitting <NUM>, frame <NUM> and cleats <NUM>, <NUM> can be formed integrally with each other in variants of the embodiment. For example, the first fitting <NUM>, the cleats <NUM> and the frame <NUM> could be formed integrally with each other, and, if desired, may also be formed integrally with the cleats <NUM>. Alternatively, the cleats <NUM> might be formed integrally with the frame <NUM> and separate from the fitting <NUM>.

Although not shown in the figures, the second section 2b can be provided with stringers and/or frames as well, in order to provide a stiffening structure for the skin portion 17b.

A method for forming the structural junction <NUM> according to the embodiment described above will be explained in the following.

Various individual components for assembling the first and second sections 2a, 2b including the junction <NUM> are provided in steps S0a, S0b, schematically shown in <FIG>.

More specifically, step S0a includes providing the first fitting <NUM> and the pressure bulkhead skin <NUM>, while step S0b includes providing the second fitting <NUM>.

In a first step S1, the first fitting <NUM> is attached to the fuselage skin portion 17a. This may be accomplished, for example, by connecting the first outer flange <NUM> to the skin portion 17a using rivets, not shown in the Figures.

In a second step S2, the pressure bulkhead skin <NUM> is attached to the inner flange <NUM> of the first fitting <NUM>. This may be accomplished, for example, by connecting the overlapping inner flange <NUM> and edge portion of the bulkhead skin <NUM> using rivets.

Within a process of assembling the fuselage <NUM>, the first and second steps S1, S2 is in particular part of a sub-process SPa of pre-assembling the first fuselage section 2a. The sub-process SPa may comprise further assembly steps, and in particular additionally comprises steps of providing the frame <NUM>, connecting the frame <NUM> to the stringers <NUM> and to the skin portion 17a using the cleats <NUM>, and connecting the frame <NUM> to the first fitting <NUM> via the tab <NUM>, using the cleats <NUM>.

In a third step S3, the second fitting <NUM> is attached to the fuselage skin portion 17b, for example also by riveting.

<FIG> shows that with the shape in particular of the first fitting <NUM>, comprising the inner flange <NUM> extending over the inner end <NUM> of the second web <NUM>, both the first outer flange <NUM> as well as the inner flange <NUM> can be accessed well by the worker for establishing the connection with the skin portion 17a and bulkhead skin <NUM>, respectively, when pre-assembling the first section 2a.

Within the process of assembling the fuselage <NUM>, the third step S3 is in particular part of a sub-process SPb of pre-assembling the second fuselage section 2b.

Sub-processes SPa and SPb may be performed in parallel.

In a fourth step S4, after pre-assembly of each of the first and second fuselage sections 2a and 2b has been completed, the first and second fuselage sections 2a and 2b are joined to form the junction <NUM>, and the first fitting <NUM> and the second fitting <NUM> are connected at least using the tension bolts <NUM>.

Further, the first and second fittings <NUM>, <NUM> may be connected, as described above, in the intermediate regions <NUM>, <NUM> by fasteners transmitting shear, in particular by rivets.

The orbital junction <NUM> between the sections 2a, 2b at the rear pressure bulkhead interface and the method of the embodiment thus make it possible to reduce the assembly lead time, as the first and second sections 2a, 2b can each be pre-assembled before joining them at the position of the rear pressure bulkhead <NUM>. Thus, the number of components to be handled and connected during fuselage assembly can be reduced as well. Also, ergonomics for the workers during assembly of sections and of the fuselage is improved.

<FIG> schematical displays the step of joining the pre-assembled sections 2a and 2b, with <FIG> showing both sections in their pre-assembled state before being joined via junction <NUM>, and <FIG> showing the sections 2a, 2b in a joined state in which the junction <NUM> is completed. The junction <NUM> makes it possible to conveniently pre-assemble both sections 2a, 2b in the tapering tail region of the fuselage <NUM>, with the aid of the arrangement of the first and second main surfaces <NUM>, <NUM> with respect to the edges 12a, 12b. In the assembled fuselage <NUM>, substantially the entire longitudinal tensile load between the sections 2a and 2b will be supported by the tension bolts <NUM>.

Although the invention has been completely described above with reference to preferred embodiments, the invention is not limited to these embodiments but may be modified in many ways.

Claim 1:
Aircraft or spacecraft fuselage (<NUM>) comprising a fuselage skin (<NUM>) and divided in at least a first and a second fuselage sections (2a, 2b) which, when assembled, form the fuselage (<NUM>), the fuselage (<NUM>) including a structural junction (<NUM>) which comprises
a first fitting (<NUM>) attached to a portion (17a) of the fuselage skin (<NUM>) in the first fuselage section (2a),
a second fitting (<NUM>) attached to a portion (17b) of the fuselage skin (<NUM>) in the second fuselage section (2b), and
a pressure bulkhead skin (<NUM>) attached to an inner flange (<NUM>) of the first fitting (<NUM>), the inner flange (<NUM>) being spaced apart from the fuselage skin (<NUM>) towards an inner space (<NUM>) enclosed by the fuselage skin (<NUM>) when the fuselage (<NUM>) is assembled;
wherein the pressure bulkhead skin (<NUM>) is, in use, a skin of a rear pressure bulkhead (<NUM>) of the aircraft or spacecraft (<NUM>), wherein with respect to the rear pressure bulkhead (<NUM>), the first fuselage section (2a) is a forward section and the second fuselage section (2b) is a rearward section;
wherein the first fitting (<NUM>) and the second fitting (<NUM>) are connected, during assembling of the fuselage (<NUM>), at least using a plurality of tension bolts (<NUM>), wherein the tension bolts (<NUM>) each are arranged and adapted to transfer at least tensile loads, in a direction across adjacent edges (12a, 12b) of the first and second fuselage sections (2a, 2b) in a region where the first and second fuselage sections (2a, 2b) are joined, between the first and second fittings (<NUM>, <NUM>); and
wherein the first fitting (<NUM>) further comprises a first outer flange (<NUM>) for joining the first fitting (<NUM>) to the portion (17a) of the fuselage skin (<NUM>) in the first fuselage section (2a) and a first web (<NUM>) connecting the inner flange (<NUM>) and the first outer flange (<NUM>), and wherein the second fitting (<NUM>) comprises a second outer flange (<NUM>) for joining the second fitting (<NUM>) to the portion (17b) of the fuselage skin (<NUM>) in the second fuselage section (2b) and a second web (<NUM>) connected to the second outer flange (<NUM>).