Continuous fuselage connection

This application claims the benefit of the filing date of the German Patent Application No. 10 2005 038 856.6 filed August 17, 2005, and the US Provisional Application No. 60/709,050 filed August 17, 2005,the disclosures of which is hereby incorporated herein by reference.

Technical field

The present invention relates to a connection system and a method for attaching a tail unit surface to the fuselage of an aircraft.

Background to the invention

Up to now in aircrafts the vertical tail unit is attached to the fuselage with the use of several horizontally attached bolts. In this arrangement the walls of the vertical tail units are first inserted into fork-like apertures in the fuselage, and are subsequently attached by means of the horizontally aligned bolts. Bushes that in each instance are attached to the centre box shells and to the fuselage mountings are used to accommodate the bolts. In particular in the case of the vertical tail unit of an aircraft, very considerable transverse forces are experienced over the entire tail unit surface, as a result of which extensive tensile and compressive forces occur in the base region of the vertical tail unit. The bolts therefore have to deflect very considerable tensile and compressive forces into the fuselage so that in order to transfer these forces the walls of the centre box shells in the connection region need to comprise very large thickened parts so as to provide a stable structure. Furthermore, the fuselage mountings to which the bolts are attached on the fuselage must comprise corresponding dimensions. Moreover, in the region of the bolts in the fuselage mountings a high load concentration of the forces to be transferred is experienced so that their dimensioning has to be additionally adapted.

Presentation of the invention

It is an object of the invention to provide a stable and light-weight connection system for attaching a tail unit surface.

This object is met by an attachment system and a method for attaching a tail unit surface to the fuselage of an aircraft, as well as by the use of the attachment system in an aircraft, with the features according to the independent claims.

In the present invention the term "tail unit" refers to a surface of an aircraft, such as for example a vertical tail unit or a horizontal tail unit.

The term "attachment surface" refers to a surface of an aircraft, on which surface the tail units can be attached, for example a fuselage.

According to a first exemplary embodiment of the invention an attachment system for attaching a tail unit to an attachment surface of an aircraft is provided, wherein the attachment system comprises a tail unit, an attachment surface and a mounting with a first bearing surface that is designed to rest against the tail unit, and comprises a second bearing surface that is designed to rest against the attachment surface. In this arrangement the first bearing surface and the second bearing surface, of which there is at least one, comprise a common line of contact. The first bearing surface comprises a first surface and the second bearing surface comprises a second surface, wherein the angle of the first surface and the second surface differs from 0° and 180°.

According to an exemplary embodiment of the invention a method for attaching a tail unit to an attachment surface of an aircraft is provided, which method involves the steps of placing a mounting with a first bearing surface to a tail unit, and in a further step placing a mounting with a second bearing surface to an attachment surface, wherein the first bearing surface and the second bearing surface comprise a line of contact. The first bearing surface comprises a first surface and the second bearing surface comprises a second surface, wherein the angle of the first surface and the second surface differs from 0° and 180°.

In a further exemplary embodiment the attachment system is used for attaching a tail unit to an attachment surface of an aircraft. In a further exemplary embodiment an aircraft with a system for attaching a tail unit to an attachment surface is provided.

The attachment system according to the invention provides a connection option that is a clearly lighter-weight and more stable solution when compared to the hitherto known connection systems. Up to now, for example, large thickened parts had to be provided in the base regions of the tail units and on the fuselage, in order to predominantly transfer to the fuselage the bending moments that act on the vertical tail unit. Such thickened parts result in very considerable additional weight and in significantly increased costs during production. Due to the connection system according to the invention, by means of using a mounting, there is no need to provide such thickened parts of the tail units in the base regions and in the fuselage. At the same time, stress concentrations are avoided and thus homogeneous transmissibility of very considerable forces is made possible. It is thus possible to avoid unnecessary weight and to save costs due to reduced material usage. The attachment system according to the invention can for example connect a tail unit to a fuselage, or it can interconnect two tail unit surfaces. It is, for example, possible in the case of V-tails to

connect the two vertical tail units by the attachment system according to the invention.

According to another exemplary embodiment of the invention the first bearing surface and the tail unit comprise a first contact region with a first surface shape, wherein the first surface shape of the first contact region corresponds to the first surface shape of the tail unit. Furthermore, the second bearing surface and the attachment surface comprise a second contact region with a second surface shape, wherein the second surface shape of the second contact region corresponds to the shape of the attachment surface. In this way a situation is achieved in which the mounting conforms to the attachment surface or to the shape in the contact region of the tail unit, thus making it possible to establish a connection having positive fit.

According to another exemplary embodiment of the invention the first bearing surface and the second bearing surface of the mounting extend along the course of the line of contact. In this way the mounting extends, for example, along the entire line of contact between the tail unit and the attachment surface. This makes it possible to achieve homogeneous force transmission along the entire line of contact so that stress peaks are avoided.

According to another exemplary embodiment of the invention the tail unit comprises an inside and an outside, wherein the first bearing surface is designed to rest against at least one of the insides and/or outsides of the tail unit. Modern designs of tail units comprise a thin-walled outer skin with inner reinforcements, for example by way of braces or a framework. This makes it possible to attach the mounting to an inside or to an outside of a tail unit wall or of a tail unit surface. Attaching the mounting to the inside of the first or the second tail unit surface results, on the outside, in a smooth surface without edges that thus provides optimum air flow characteristics so that

airflow losses as a result of turbulence at comers or edges of the mounting are avoided.

According to yet another exemplary embodiment of the invention the attachment system further comprises at least one first connection element and a second connection element, wherein the tail unit is connected to the first bearing surface by way of the first connection element, and the attachment surface is connected to the second bearing surface by way of the second connection element.

According to yet another exemplary embodiment of the invention the first connection elements or the second connection elements at least in a first row are arranged parallel in relation to the line of contact. According to yet another exemplary embodiment of the invention at least the first connection elements or the second connection elements comprise a multitude of rows parallel to the line of contact. In this way the connection elements can transfer significantly greater loads. For example, the various rows of connection elements can be arranged so as to be offset in relation to each other, so as in this way to provide optimum load distribution of the forces to be transferred.

According to another exemplary embodiment of the invention the first connection element comprises a first direction of extension and the second connection element comprises a second direction of extension, wherein the first direction of extension and the second direction of extension differ from each other. In this way it becomes possible to optimally introduce tensile and compressive forces, for example from a tail unit to the fuselage.

According to yet another embodiment of the invention the first direction of extension of the first connection element is arranged so as to be essentially perpendicular in

relation to the tail unit while the second direction of extension of the second connection element is arranged so as to be essentially perpendicular in relation to the attachment surface. This results in optimal and homogeneous load distribution and in optimal transfer of the forces, for example of two surfaces arranged so as to be perpendicular in relation to each other. In this way the tensile and compressive forces that are experienced can be transferred better.

According to another exemplary embodiment of the invention at least one of the first and second connection elements is a disconnectable connection. In this way particular installation procedures are significantly facilitated because it becomes possible to flexibly attach the mounting to the respective surfaces. In this arrangement the first connection element and the second connection element, of which there is at least one each, can be selected from the group comprising screw connections, bolt connections, welded connections, adhesive connections, riveted connections and plug-type connections.

According to another exemplary embodiment of the invention the first bearing surface comprises a first tooth profile, and the tail unit in the first contact region comprises a second tooth profile, wherein the second tooth profile of the tail unit is designed to engage the first tooth profile of the first bearing surface.

According to another exemplary embodiment of the invention the second bearing surface comprises a third tooth profile and the attachment surface in the second contact region comprises a fourth tooth profile, wherein the fourth tooth profile of the attachment surface is designed to engage the third tooth profile of the second bearing surface. In this way, by means of the engaging tooth profiles, highly continuous force transfer is achieved without the occurrence of undesirable stress concentration so that significantly greater forces can be transferred.

According to another exemplary embodiment of the invention at least one of the tooth profiles is detachably attached. In this way installation of the connection system is facilitated.

In a further exemplary embodiment of the invention each tooth profile comprises elevations and indentations with flanks. The flanks of the tooth profiles can be designed so as to be at right angles in relation to the direction of the transferred forces. In this way considerably greater loads can be transferred and damage to the tooth profiles can be avoided.

In a further exemplary embodiment of the present invention each tooth profile can be selected from the group comprising dovetail shapes, T-groove shapes, longitudinal groove shapes and trapezoidal groove shapes.

In a further exemplary embodiment of the invention compensating media are attached between the flanks of the tooth profiles such that an even load distribution results. In order to provide ideal transmission of forces the individual tooth profiles have to be manufactured to extremely exact tolerances so that no stress peaks occur as a result of inexactly made tooth profiles. Since this results in very high production costs, compensating media are attached in between the teeth, i.e. in between the flanks of the teeth, so that there is no need to produce to such exacting and expensive tolerances. The compensating media can for example comprise a material such as a soft metal, a wood fibre material or a plastic material such as PTFE.

According to a further exemplary embodiment of the present invention the mounting comprises a third bearing surface or a multitude of bearing surfaces against which tail unit surfaces and/or fuselages come to rest. This means that it is possible, for

example, to attach two tail unit surfaces to a fuselage with the use of only one mounting.

According to a further exemplary embodiment of the present invention a fuselage mounting is inserted in between at least one of the first bearing surfaces and the tail unit. According to a further exemplary embodiment of the present invention a fuselage mounting is inserted in between at least one of the second bearing surfaces and the attachment surface. This fuselage mounting can bridge any differences in shape, for example between the fuselage and the mounting, and in this way can optimise load distribution. In this way it is possible from an unfavourably curved shape to create a straight supporting surface by way of the adaptive fuselage mounting, as a result of which any tensile and compressive forces can be transferred to the fuselage in a significantly better manner.

According to another exemplary embodiment of the invention at least one of the first and second bearing surfaces comprise at least one slot arrangement. By means of this single or multiple slot arrangement a significant reduction in stiffness fractures, and in addition better load distribution, can be achieved.

In this arrangement the connection system according to the invention can connect vertical tail units and horizontal tail units with other attachment surfaces such as for example the fuselage. It is thus possible, for example, to attach V-tails or a horizontal tail unit or a vertical tail unit to an attachment surface jointly by using one mounting.

According to a further embodiment of the method in a further step the first bearing surface with a first contact region is matched to the contour of the tail unit, and in a further step the second bearing surface with a second contact region is matched to the contour of the attachment surface.

According to a further exemplary embodiment of the method in a further step the first bearing surface and the second bearing surface are matched to the course of the line of contact.

According to a further exemplary embodiment of the method the first bearing surface is attached at least to one of the insides and outsides of the tail units and attachment surfaces.

According to a further exemplary embodiment of the method in a further step the tail unit is connected to the first bearing surface by means of a first connection element, and in a further step the tail unit is connected to the second bearing surface by means of a second connection element.

According to a further exemplary embodiment of the method in a further step the tail unit is connected to the first bearing surface by means of a first and second tooth profile, and/or in a further step the attachment surface is connected to the second bearing surface by means of a third and fourth tooth profile.

The embodiments of the attachment system also apply to the method, and vice versa.

The connection system according to the invention and the method according to the invention thus provide a significantly lighter and more effective system of connecting tail unit surfaces to fuselages. The expenditure and the weight of the structure can be reduced enormously with the use of the present invention.

Furthermore, with the use of the innovative connection elements the time required for installing tail units to fuselages can be significantly reduced.

Brief description of the drawings

Below, for further illustration and to provide a better understanding of the present invention exemplary embodiments are described in more detail with reference to the enclosed drawings.

Fig. 1 shows a known connection system for connecting a tail unit to a fuselage;

Fig. 2 shows a diagrammatic illustration of a vertical tail unit that has been attached to the fuselage with the use of an attachment system according to an embodiment of the invention;

Fig. 3 shows a diagrammatic illustration of an embodiment of the present invention, in which the vertical tail unit is attached to the fuselage with the use of a tooth profile;

Fig. 4 shows an enlarged diagrammatic illustration of a vertical tail unit that is attached to the fuselage by means of a tooth profile;

Fig. 5 shows a diagrammatic illustration of a rectangular tooth profile according to one exemplary embodiment of the invention;

Fig. 6 shows a diagrammatic illustration of a dovetail profile with an angle α according to one exemplary embodiment of the invention; and

Fig. 7 shows a diagrammatic illustration of the connection system.

Detailed description of exemplary embodiments

Identical or similar components in different figures are provided with the same reference characters.

The illustrations in the figures are diagrammatic and not to scale.

Fig. 2 is a diagrammatic illustration of the attachment system 1 according to an embodiment of the invention for attaching a tail unit 2 to an attachment surface 3 of an aircraft. In this arrangement a mounting 6 comprises a first bearing surface 17 that is designed to rest against a tail unit 2, and a second bearing surface 18 that is designed to rest against the attachment surface 3. In this arrangement the first bearing surface 17 and the second bearing surface 18 comprise a common line of contact 16, wherein the first bearing surface 17 and the second bearing surface 18 differ from each other in that their surfaces are at an angle that differs from 0° and 180°.

Fig. 1 shows a commonly used connection system of a vertical tail unit 2 with a fuselage 3. As a result of the unidirectional horizontally attached bolts 7 that connect the base of the vertical tail unit 2 to the fuselage 3, thickened parts in the base region of the vertical tail unit are required in order to reinforce the structure. This results in a significant increase in weight and in increased costs for materials.

Fig. 2 also shows the structure of modern vertical tail units 2. In this arrangement a vertical tail unit 2 comprises two walls, each comprising an inside 4 and an outside 5. At the base of the tail unit 2, on the so-called centre box shell, in a first contact region 13 a mounting 6, 6' is attached, which mounting extends along the length of the vertical tail unit 2 and conforms to the shape of the first contact region 13. At the same time the mounting is attached in a second contact region 14 to a fuselage 3 with

the use of a second bearing surface 18. This second bearing surface 18 has the same shape as the fuselage 3 in the second contact region 14.

In this arrangement the first bearing surface 17 and the second bearing surface 18 of the mounting 6, 6' are each attached to the vertical tail unit 2 or to the fuselage 3 by means of attachment elements 7, T . At the same time a fuselage mounting 15 can be attached between the fuselage 3 and the mounting 6, 6' so as to achieve better load distribution between the contour of the fuselage 3 and the contour of the mounting 6, 6'.

The connection elements 7, T can also extend through both walls of the vertical tail unit 2 and can thus connect a second outer mounting 6' at the same time. In this arrangement a distance sleeve 7" can be inserted between the two walls 2', 2". Furthermore, the directions of extension of the connection elements 7, T are in each case oriented along the normal surface line of the respective bearing surface 17, 18. In this way the flow of forces is significantly enhanced and any transfer of additional moments by one-sided connection is prevented.

In order to achieve an improved connective strength there is also the option of designing the connection elements 7, T, apart from the shape shown in Fig. 2, in several rows parallel to the line of contact 16. For example, the connection elements 7, T can comprise a first row parallel to the line of contact 16, and furthermore comprise at least one second row of connection elements 7, T parallel to the line of contact 16. In this arrangement any number of rows can be attached, most advantageously three to four rows.

Fig. 3 shows a design that is similar to that shown in Fig. 2, except that instead of the connection element 7, T a tooth profile with a first tooth rack 8 and with a second

tooth rack 9 has been shown. By means of this tooth profile 8, 9 the mountings 6 and 6' can ideally be connected to the vertical tail unit 2. As an option, the mounting 6, 6' can also be attached to the fuselage 3 by way of a third and fourth tooth profile. In Figs 2 to 4 the mounting 6, 6' conforms to the respective bearing surface 17, 18 of the vertical tail unit 2 or of the fuselage 3. By way of the tooth profile 8, 9 shown, forces can be transferred to the fuselage 3 in an extremely homogeneous manner. Excessive load concentrations can effectively be prevented. In each instance, in longitudinal direction of the first and second tooth profile 8, 9, slot arrangements 12 are shown which play a part in reducing stiffness cracks, thus resulting in improved load distribution. The tooth profiles 8, 9 in turn can be attached to the inside or outside of the walls of a vertical tail unit 2.

Fig. 4 shows a further view of a vertical tail unit 2 that is attached to a fuselage 3 by way of the connection system 1. The illustration clearly shows that if a tooth profile is used to connect the vertical tail unit 2 to the fuselage 3 the design can be kept extremely slim in the first contact region 13.

Fig. 5 is a diagrammatic illustration of the first tooth rack 8 and the second tooth rack 9 which engage each other. In this arrangement each tooth profile 8, 9 comprises flanks 10 which in Fig. 5 are formed in a rectangular design. For better and more homogeneous force transfer compensating media 11 have been placed between the flanks 10. If, as shown in this example, tensile or compressive forces act on the vertical tail unit 2, then loads are developed in a vertical direction. In this arrangement the force is optimally transferred if the flanks 10 are designed so as to be at a right angle in relation to the direction of the forces to be transferred.

Fig. 6 also shows the first tooth rack 8 and the second tooth rack 9, wherein the tooth profile is designed so as to be dovetailed. In this arrangement the flanks 10 are

arranged at a particular angle α, which indicates the angle of the flanks 10 in relation to the direction of transfer of the force F and of the load.

Fig. 7 shows an overall view of a vertical tail unit 2. On the base of the vertical tail unit 2 the connection system 1 is shown that connects the vertical tail unit 2 to the fuselage 3. It is clearly evident that without any thickened part in the base region of the vertical tail unit 2 an optimal connection system 1 is created, and at the same time a more stable and more light-weight connection option can be provided.

In addition it should be pointed out that "comprising" does not exclude other elements or steps, and "a" or "one" does not exclude a plural number. Furthermore, it should be pointed out that features or steps which have been described with reference to one of the above embodiments can also be used in combination with other features or steps of other embodiments described above. Reference characters in the claims are not to be interpreted as limitations.

List of reference characters:

1 Aircraft

2 Tail unit 3 Fuselage / attachment surface

4 Inside of a tail unit wall

5 Outside of a tail unit wall 6/ 6' Mounting

11 T First/second connection element 7" Distance sleeve

8 First tooth profile

9 Second tooth profile

10 Flanks

11 Compensating medium 13 First contact region

14 Second contact region

15 Fuselage mounting

16 Line of contact

17 First bearing surface 18 Second bearing surface