WO2014177589A1

WO2014177589A1 - Aircraft for vertical take-off and landing with hinged and bendable wings

Info

Publication number: WO2014177589A1
Application number: PCT/EP2014/058765
Authority: WO
Inventors: Johannes Reiter
Original assignee: Johannes Reiter
Priority date: 2013-04-30
Filing date: 2014-04-29
Publication date: 2014-11-06
Also published as: GB201307739D0

Abstract

The present invention describes an aircraft (100) for vertical take-off and landing. The aircraft (100) comprises a fuselage (101) comprising a fuselage nose (103) and a fuselage tail (104), a wing arrangement (110) comprising a longitudinal wing axis and a coupling device (120) which couples the wing arrangement (110) to the fuselage (101), such that the wing arrangement (110), in a fixed-wing flight mode, does not rotate around the fuselage (101), and such that the wing arrangement (110), in a hover flight mode, is tilted around the longitudinal wing axis with respect to its orientation in the fixed-wing flight mode and that the wing arrangement (110) rotates around the fuselage (101). The wing arrangement (110) is coupled to the coupling device (120) such that in the hover flight mode a wing tip of the wing arrangement (110) is movable in a direction to the fuselage nose (103) or to the fuselage tail (104).

Description

Aircraft for vertical take-off and landing with hinged and bendable wings

FIELD OF THE INVENTION

The present invention relates to an aircraft for vertical take-off and landing comprising a bendable or pivotable wing arrangement and to a method for operating an aircraft for vertical take-off and landing comprising a bendable or pivotable wing arrangement.

BACKGROUND OF THE INVENTION

It is an aim to have aircrafts that are able to start and land without a runway for example. Hence, in the past several developments for so called Vertical Take-Off and Landing aircraft (VTOL) have been done. Conventional VTOL- Aircraft need a vertical thrust for generating the vertical lift. Extreme thrust for vertical take-off may be produced by big propellers or jet engines.

Propellers may have the disadvantage in travel flight of an aircraft due to a high drag.

An efficient solution for a hover flight capable aircraft is performed by helicopters, using e.g . a big wing area. In a known system, an aircraft comprises an engine for vertical lifting the aircraft (e.g . a propeller) and e.g . a further engine for generating the acceleration of the aircraft in a travel mode up to a desired travelling speed .

In the hover flight mode, the rotating wings or blades of an aircraft (e.g. a helicopter) generate the vertical lift. The rotating wings comprise a chord line, wherein an angle between the chord line and the streaming direction of the air may be called angle of attack. A higher angle of attack generates a higher lift and a lower angle of attack generates a lower lift but also less drag. In order to achieve a higher efficiency of the rotating wings it may be helpful to adjust the angle of attack. Thus, the wings may be tilted around its longitudinal axis.

In the hover flight mode, the rotating wings generate lifting forces for lifting the aircraft. Different loads and load changes act onto the wings during the rotation of the wings. Between the load changes flapping hits act onto the wings within each rotation. Furthermore, wind gusts and side winds acts onto the rotating wings which causes further flapping hits. Hence, high bending cycle loads acts onto the rotating wings.

OBJECT AND SUMMARY OF THE INVENTION

It may be an object of the present invention to provide an aircraft for vertical takeoff and landing comprising a wing arrangement with a proper lifetime. This object may be solved by an aircraft for vertical takeoff and landing and by a method for operating an aircraft for vertical takeoff and landing according to the independent claims.

According to a first aspect of the present invention, an aircraft for vertical takeoff and landing is presented . The aircraft comprises a fuselage comprising a fuselage nose and a fuselage tail, a wing arrangement comprising a longitudinal wing axis and a coupling device which couples the wing

arrangement to the fuselage.

The coupling device couples the wing arrangement to the fuselage, such that the wing arrangement does not rotate around the fuselage axis in a fixed win flight mode and such that the wing arrangement, in hover flight mode, is tilted around the longitudinal wing axis with respect to its orientation in the fixed wing flight mode and that the wing arrangement rotates around the fuselage. In particular, the wing arrangement is coupled to the coupling device such that in the hover flight mode a wing tip of the wing arrangement is movable in a direction to the fuselage nose or to the fuselage tail.

According to a further aspect of the present invention, a method for operating an aircraft for vertical takeoff and landing is presented . The aircraft is converted in a fixed wing flight mode by arranging the wing arrangement such that a fixed wing flight is enabled . Furthermore, the aircraft is converted in a hover flight mode by tilting the wing arrangement around a longitudinal wing axis and by rotating the wing arrangement around the fuselage of the aircraft. The fuselage comprises a fuselage nose and a fuselage tail, wherein the wing arrangement is coupled to the fuselage by a coupling device. The wing arrangement is coupled to the coupling device such that in the hover flight mode a wing tip of the wing arrangement is movable in a direction to the fuselage nose or to the fuselage tail.

The above described aircraft provides the hover flight mode and the fixed wing flight mode. In a hover flight mode, the wing arrangement is rotating around a rotary axis (e.g. a fuselage axis or an axis which comprises an angle to the fuselage axis) around the fuselage, so that due to the rotation of the wing through the air a lift is generated even without a relative movement of the aircraft (i.e. the fuselage) through the air. The fuselage may be rotatable together with the wing arrangement around the rotary axis. Alternatively, the wing arrangement may be rotatable with respect to the fuselage, so that only the wing arrangement rotates in the hover flight mode for generating lift.

Moreover, if the wing arrangement rotates in the hover flight mode, a stabilizing moment (e.g. a gyroscopic moment, i.e. a conservation of angular momentum) for stabilizing the aircraft is generated . In a fixed-wing flight mode, the wing arrangement is fixed to the fuselage without having a relative motion between the wing arrangement and the fuselage, so that by a forward motion of the aircraft through the air lift is generated by the wing

arrangement by a forward movement of the wing arrangement through the air.

The aircraft according to the present invention may be a manned aircraft or an unmanned aircraft vehicle (UAV). The aircraft may be e.g . a drone that comprises for example a wing span of approximately 1 m to approximately 40 m (meter) or more with a weight of approximately 4 kg to 200 kg (kilograms).

The wing arrangement comprises a longitudinal wing axis, wherein the longitudinal wing axis is the axis around which the wing arrangement is tiltable with respect to the fuselage. The longitudinal wing axis may be defined by the run of a main wing spar or by a bolt (e.g. one of the below described fixing elements) that connects for example a wing root of the wing arrangement with the fuselage. The wing arrangement is mounted with its wing root to the fuselage, wherein at an opposite end of the wing arrangement with respect to the wing root the wing tip is defined, which is a free end of the wing

arrangement. The longitudinal wing axis may be parallel e.g . with a leading edge or a trailing edge of the wing arrangement. Moreover, the longitudinal wing axis may be an axis that is approximately perpendicular to the fuselage axis and/or the rotary axis.

The wing arrangement may comprise a first wing, a second wing or a plurality of wings. Each wing may comprise an aerodynamical wing profile comprising a respective leading edge, where the air impinges and a respective trailing edge from which the air streams away from the wing . A chord line of the wing arrangement and the wings, respectively, refers to an imaginary straight line connecting the leading edge and the trailing edge within a cross-section of an airfoil . The chord length is the distance between the trailing edge and the leading edge.

The fuselage describes a main body of the aircraft, wherein in general the centre of gravity of the aircraft is located inside the area of the fuselage. The fuselage may be in one exemplary embodiment of the present invention a small body to which the wing arrangement is rotatably mounted, so that the aircraft may be defined as a so-called flying wing aircraft. In particular, the fuselage may be a section of the wing and the fuselage may comprise a length equal to the chord line (e.g . a width) of the wing. Alternatively, the fuselage comprises a length that is longer than e.g. the chord line (e.g . the width) of the wing that connects the leading edge and the trailing edge. The fuselage comprises a nose and a tail section. The wing arrangement rotates through the air and the air has a defined streaming direction with respect to the wing arrangement. A so-called angle of attack defines the alignment of the wing arrangement with respect to the streaming direction of the air, through which the wing arrangement moves (i.e. in the hover flight mode and the fixed wing flight mode, respectively). The angle of attack is defined by an angle between the cord line of the wing arrangement and the streaming direction of the air which attacks and impinges at the leading edge of the wing arrangement. If the angle of attack is increased, the coefficient of lift c is increased till a critical angle of attack is reached, where generally stall occurs.

Hence, in order to control the device adequately it is necessary to adjust a predefined lift of the aircraft. The lift of the aircraft may be defined for example by the rotational speed of the wing arrangement around the rotary axis and by adjusting the angle of attack. The term "lift" denotes a force which forces the device to move along a defined direction, e.g . horizontally or vertically. In the hover flight mode, the rotating wings generate lifting forces for lifting the aircraft. Different loads and load changes act onto the wings during the rotation of the wings. Between the load changes flapping hits act onto the wings within each rotation. Furthermore, wind gusts and side winds act onto the rotating wings which cause further flapping hits. Hence, high bending cycle loads acts onto the rotating wings.

By the approach of the present invention, the coupling device which couples the wing arrangement to the fuselage provides a defined mobility and a defined maximum pivoting angle along at least one degree of freedom.

Specifically, the coupling device provides a degree of freedom (i.e. a pivoting around at least one pivoting axis) for the wing arrangement along the effective direction of the flapping hit. Hence, the wing arrangement can move with its wing tips along the effective direction of the flapping hit such that the flapping hits may be damped and are not induced with its maximum load into the structure of the wing arrangement. Hence, due to the damped loads acting on the wing arrangement, the lifetime of the wing arrangement is increased . The coupling device comprises all elements which are necessary for coupling the wing arrangement to the fuselage. In order to provide the damping of the flapping hits, the coupling device may comprise a bending section and/or a hinge mechanism as described more in detail below. According to a further exemplary embodiment, the coupling device comprises a bending section which is located between the wing arrangement and the fuselage such that, in the hover flight mode, a wing tip of the wing

arrangement is movable in a direction to the fuselage nose or to the fuselage tail. Specifically, the bending section of the coupling device may be fixed to the wing arrangement or may be formed integrally as a root section of the wing arrangement, for example. In a further exemplary embodiment of the present invention, the bending section is made of an elastically deformable material which is adapted for withstanding a plurality of bending movements without severe defects.

According to a further exemplary embodiment, the coupling device comprises a hinge which couples the wing arrangement to the coupling device.

The hinge may be formed of a ball joint type, a flexible joint or a hinge comprising pivoting pins, for example. Specifically, the hinge comprises one pivoting axis, two pivoting axes or three pivoting axes. The hinge may be formed as a flapping hinge which comprises at least one pivoting axis or a universal joint which comprises two or three perpendicular pivoting axes. The hinge may be formed with two perpendicular pivoting pins or with a ball type hinge. According to a further exemplary embodiment, the wing arrangement comprises a hollow root section, wherein the hinge is slidably coupled within the hollow root section, such that the hinge is slidable along the longitudinal wing axis between a locking position and a pivoting position. In the locking position, the hinge is located inside the root section such that a pivoting of the wing arrangement is prevented. In the pivoting position, the hinge is located outside the root section for allowing a pivoting of the wing arrangement.

Hence, in the hover flight mode, the hinge may be moved out of the hollow root section (e.g. a channel or a recess), such that the wing arrangement is movable and may pivot around the hinge. In the locking position, the hinge is located inside the hollow root section, such that the hinge is locked by the walls of the hollow root section such that the pivoting is not possible.

During rotation of the wing arrangement around the rotary axis, centrifugal forces act on the wing arrangement which try to pull the wing arrangement away from the rotary axis of the wing arrangement around the fuselage. The centrifugal force may be used such that the wing arrangement moves with a defined distance away from the fuselage such that the hinge moves out of the hollow section and is thus arranged in the pivoting position.

Alternatively, besides the centrifugal force, also an active controlling unit, such as an electrical servo motor or a hydraulic or pneumatic motor, may be used which actively moves the hinge into or out of the hollow root section. For example, according to a further exemplary embodiment, the coupling device comprises a spring which is coupled to the hinge such that a spring force of the spring pretensions the hinge to the locking position. The

predefined spring force acts onto the wing arrangement and presses the hinge in the locking position. If the centrifugal force exceeds the predefined spring force of the spring, the wing arrangement moves away from the fuselage and the hinge moves out of the hollow root section of the wing arrangement till the hinge is in the pivoting position.

Furthermore, if the aircraft is converted from the hover flight mode to the fixed wing mode and the rotational speed of the wing arrangement around the fuselage reduces, the centrifugal force reduces as well . Hence, the centrifugal force falls below the spring force of the spring, such that the wing

arrangement is pulled by the spring force closer to the fuselage and the hinge is arranged again inside the hollow root section, where it is blocked . Hence, a self-regulating coupling device may be provided, wherein the hinge is located in the pivoting position or the locking position depending on the rotational speed of the wing arrangement around the fuselage. Further controlling devices may not be necessary.

According to a further exemplary embodiment, the coupling device comprises an inner ring and an outer ring which surrounds the inner ring . The inner ring is coupled to the fuselage by an inner pivot joint such that the inner ring is pivotable around an inner pivot axis. The outer ring is coupled to the inner ring by an outer pivot joint such that the outer ring is pivotable around the outer pivot axis. The inner pivot joint and the outer pivot joint are arranged with respect to each other such that the inner pivot axis and the outer pivot axis are orientated (e.g. substantially) perpendicular with respect to each other. Hence, the wing arrangement may be supported to the aircraft by the coupling device in a gimbal mechanic manner and a cardan-mechanic manner, respectively. Specifically, the inner ring and the outer ring may form

respective gimbals wherein, each gimbal provides a respective pivoting axis for the wing arrangement with respect to the fuselage.

Furthermore, the fuselage may comprise a propulsion unit for driving the aircraft through the air in the fixed wing flight mode. However, alternatively or additionally, according to a further exemplary embodiment, the aircraft comprises a propulsion unit which is mounted to the wing arrangement.

The propulsion unit may be a jet engine, a turbo jet engine, a turbo fan, a turbo prop engine, a prop fan engine, a rotary engine and/or a propeller engine. The propulsion unit may be pivotable around the longitudinal wing axis with respect to and relative to the wing arrangement or the propulsion unit may be pivotable together with the wing arrangement. In an exemplary embodiment, the propulsion unit may be adapted for generating a thrust of 3 kg to 5 kg (kilograms). In the hover flight mode, approximately 25 kg are liftable. The aircraft for vertical take-off and landing may thus have a thrust-to-weight ratio of approximately 0,2 to 0,4, preferably 0,3.

It has to be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with reference to apparatus type claims whereas other embodiments have been described with reference to method type claims. However, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the apparatus type claims and features of the method type claims is considered as to be disclosed with this application.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Fig. 1 shows a schematical view of an aircraft according to an exemplary embodiment of the present invention, wherein a hinge of a coupling device is in a pivoting position; Fig. 2 shows a schematical view of the aircraft according to Fig . 1, wherein the hinge of the coupling device is in a locking position;

Fig. 3 shows a schematical view of a hinge which is formed in a ball joint manner according to an exemplary embodiment of the present invention;

Fig. 4 shows a schematical view of a hinge which is formed in a universal joint manner according to an exemplary embodiment of the present invention; Fig. 5 shows a schematical view of a hinge with a coupling rod according to an exemplary embodiment of the present invention;

Fig. 6 shows a schematical view of the coupling device according to an exemplary embodiment of the present invention;

Fig . 7 shows a schematical view of a wing arrangement comprising four wings according to an exemplary embodiment of the present invention;

Fig. 8 shows a schematical view of a coupling device comprising a Cardanian support of the wings according to an exemplary embodiment of the present invention; and

Fig. 9 shows a schematical view of an aircraft comprising a coupling device with a bending section according to an exemplary embodiment of the present invention. DESCRIPTION OF EXEMPLARY EMBODIMENTS

The illustration in the drawing is schematically. It is noted that in different figures, similar or identical elements are provided with the same reference signs.

Fig. 1 and Fig. 2 show an aircraft 100 for vertical takeoff and landing according to an exemplary embodiment of the present invention. Fig . 1 and Fig. 2 comprise the aircraft 100 in different flight modes. Fig. 1 shows the aircraft 100 in a hover flight mode and Fig . 2 shows the aircraft 100 in a fixed wing flight mode.

The aircraft 100 comprises a fuselage 101 comprising a fuselage nose 103 and a fuselage tail 104. The aircraft 100 further comprises a wing arrangement 110 comprising a longitudinal wing axis.

The wing arrangement 110 as shown in Figs. 1 and 2 comprises two wings, namely a first wing 111 and a second wing 112. The longitudinal wing axis is split in a first longitudinal wing axis 113 and a second longitudinal wing axis 114. The first wing 111 extends along the first longitudinal wing axis 113 from the fuselage 101 and the second wing 112 extends along the second longitudinal wing axis 114 from the fuselage 101. The first wing 111 is tiltable with a first rotary direction around the first longitudinal wing axis 113 and the second wing 112 is tiltable with a second rotational direction around the second longitudinal wing axis 114. Each wing 111, 112 comprise a respective leading edge 211 and trailing edge 212.

Accordingly, the aircraft 100 comprises a coupling device 120 which couples the wing arrangement 110 to the fuselage 101, such that the wing

arrangement 110 does not rotate around the fuselage 101 in a fixed wing flight mode. Furthermore, the coupling device 120 couples the wing arrangement 110 to the fuselage 101 such that the wing arrangement 110 and its wings 111, 112, respectively, are tiltable around the respective longitudinal wing axes 113, 114 with respect to its orientation in the fixed wing flight mode. Furthermore, in a hoover flight mode, the wing arrangement 110 is rotatable around the fuselage 101. For example, the wing arrangement 110 may rotate around a fuselage axis 102.

The wing arrangement 110 is coupled to the coupling device 120 such that in the hoover flight mode, a wing tip of the wing arrangement 110 is movable in a direction to the fuselage nose 103 or to the fuselage tail 104 (moving direction is indicated in Fig. 1 with the arrows).

In the exemplary embodiment shown in Fig . 1 and Fig . 2, the coupling device 120 comprises a hinge 121 which couples the respective wings 111, 112 to the fuselage 101.

According to an exemplary embodiment, the coupling device 120 comprises a sleeve 105 which at least partially surrounds the fuselage 101, wherein the sleeve 105 may be rotatable together with the wing arrangement 110 around the fuselage 101. The sleeve 105 and the respective coupling of the wing arrangement 110 to the fuselage 101 are shown in more detail in Fig . 6.

The hinge 121 may be a flapping hinge or a universal joint (see exemplary embodiments for example in Fig. 3 to Fig . 5).

In the hoover flight mode, the wing arrangement 110 rotates around the fuselage axis 102. Thereby, lift for the aircraft 100 is generated such that the hoover flight mode is enabled . Due to the rotation of the wing arrangement 110 around the fuselage axis 102, a centrifugal force Fc is generated which pulls the respective wings 111, 112 away from the fuselage 101. For this reason, the hinge 121 is in a pivoting position. For example, the hinge 121 comprises a wing section which is coupled to the wing arrangement 110 and a coupling section which is coupled to the coupling device 120. The wing section and the coupling section of the hinge 121 may be pivotable with respect to each other. The coupling section is fixed to the sleeve 105 or directly to the fuselage 101, respectively. The wing section is non-pivotably coupled to the wing arrangement 110. As shown in Fig . 1, the wing section may comprise a rod 501, which is shown more in detail in Fig. 5. The rod 501 may form part of the spar of the respective wings 111, 112, respectively. The rod 501 may be slidably inserted inside a hollow root section 115 which is formed within the wing arrangement 110 (i.e. the first wing 111 and/or the second wing 112). The hinge 120 and specifically the rod 501 are slidably coupled along the longitudinal wing axis 112, 113 within the hollow root section 115. In a locking position (see Fig . 2), the hinge 121 is located inside the hollow root section 115 such that the pivoting of the wing

arrangement 110 is prevented . In the pivoting position (see Fig . 1), the hinge 121 is located outside the hollow root section 115 for allowing a pivoting of the wing arrangement 110. Additionally, the coupling device 112 comprises a spring 122 which is coupled to the hinge 121 and specifically to the rod 501, such that a spring force Ff of the spring 122 pretensions the hinge 121 to the locking position.

As shown in Fig . 1 and Fig . 2, the spring 122 is arranged inside the hollow root section 115, such that the spring 122 pulls the respective wings 111, 112 closer to the fuselage 101. The spring 120 may thereby be formed as an extension spring . In alternative embodiments, also compression springs may be used. Hence, if the rotational speed of the wing arrangement 110 around the fuselage 101 increases, the centrifugal force Fc is at some point higher than the spring force Ff, such that the wings 111, 112 moves away from the fuselage 101 and the hinges 121 slide out of the hollow section 115 in the pivoting position. Hence, in the hoover flight mode, the wings 111, 112 may move to the fuselage nose 103 or to the fuselage tail 104 so that the loads acting on the wings 111, 112 in the hoover flight mode may be damped and reduced.

Furthermore, the coupling device 120 may comprise an arrester unit which stops a pivoting of the respective wings 111, 112 at a maximum pivoting angle β.

Furthermore, a damping element may be attached to the hinge 121 for damping a pivoting of the respective wings 111, 112 in the direction to the fuselage nose 103 or to the fuselage tail 104.

The aircraft may further comprise respective tail wings 106 for providing a proper control of the aircraft.

Additionally, respective propulsion units 130, such as propeller engines, may be attached to the respective wings 111, 112 and/or to the fuselage 101.

Fig. 3 shows an exemplary embodiment of the hinge 121. The hinge 121 may be formed in a ball and joint hinge manner. The hinge 121 may comprise a first hinge part 321 which may form the above-described coupling section and a second hinge part 322 which may form the above-described wing section of the hinge 121. For example, the fuselage or the sleeve 105 is coupleable to the first hinge part 321 and the wing arrangement 110 is coupleable to the second hinge part 322. The first hinge part 321 may form a joint socket into which a ball-shaped section of the second hinge part 322 may be fixed . Fig. 4 shows a further exemplary embodiment of the hinge 121, wherein the first hinge part 321 comprises a first pivoting pin to which the second hinge part 322 is coupled . The second hinge part 322 comprises a second pivoting pin to which the first hinge part 321 is coupled. The first pivoting pin and the second pin are orientated perpendicular with respect to each other.

Fig. 5 shows an exemplary embodiment of the coupling device 120. In Fig. 5, the first hinge part 321 and the second hinge part 322 of the hinge 121 are shown. The hinge 121 in Fig . 5 is formed similar to the hinge 121 shown in Fig. 3, for example. The coupling rod 501 is coupled to the second hinge part 322. The rod 501 is slidably arranged within a respective hollow root section 115 of the wings 111, 112 as shown in Fig . 1 and Fig . 2. At the end of the rod 501, the spring 122 (see Fig. 1) is attachable.

Fig. 6 shows an exemplary embodiment of a coupling device 120 which couples the wing arrangement 110 to the fuselage 101.

The coupling device 120 comprises the sleeve 105 which surrounds the fuselage 101. The sleeve 105 is slidable along the fuselage axis 102 and rotatable around the fuselage axis 102. The wing arrangement 110 is fixed by a second fixing element 602, such as a fixing bolt, to the fuselage 101. The second fixing element 602 is rotatable around the fuselage 101 but is not coupled to the sleeve 105. The wing arrangement 110 is rotatable around the second fixing element 602. Furthermore, a first fixing element 601 couples the wing arrangement 110 to the sleeve 105. The first fixing element 601 is relatively movable with respect to the fuselage 101.

Furthermore, the sleeve 105 comprises an elongated through-hole 607 through which the second fixing element 602 is guided. If the sleeve 105 moves along a sliding direction 606 along the fuselage 101, the sleeve 105 is not blocked by the second fixing element 602. During converting of the aircraft 100 between the fixed wing flight mode and the hoover flight mode, the sleeve 105 is moved along the fuselage axis 101. Thereby, the sleeve 105 moves the first fixing element 601 along the fuselage 101 which causes the wing arrangement 110 to rotate around the second fixing element 602, which is spatially fixed to the fuselage 101. Thereby, the angle of attack a which defines an angle between the cord line 603 of the wing arrangement 110 and the flowing direction 604 of the air is adjustable. Fig. 7 shows a further exemplary embodiment of the wing arrangement 110 of the aircraft. The wing arrangement 110 of the aircraft 100 shown in Fig. 7 comprises four wings, namely a first wing 111, a further first wing 711, the second wing 112 and the further second wing 712. The further first wing 711 and the further second wing 712 comprise a smaller wing span with respect to the first wing 111 and to the second wing 112. The propulsion units 130 may be attached to the further first wing 711 and to the further second wing 712, respectively. Hence, the propulsion units 130 may be located close to the fuselage 101. The respective wings 111, 112, 711, 712 are fixed in particular to the sleeve 105.

The critical flapping hits and the high bending cycle load act in particular at the longer first wing 111 and second wing 112, because the longer first wing 111 and second wing 112 generate a higher lift in comparison to the smaller further first wing 711 and further second wing 712.

Hence, it may be only necessary to provide between the sleeve 105 and the first wing 111 and/or the second wing 112 respective hinges 121.

Fig. 8 shows a further exemplary embodiment of the coupling device 120. The coupling device 120 comprises the sleeve 105 which is coupleable to the fuselage 101. In Fig . 8, only a lower part of the fuselage 101 is shown. For sake of clarity, an upper part of the fuselage 101 is not shown in Fig. 8. The sleeve 105 may be coupled to a coupling base 805 of the fuselage 101. To the sleeve 105, an inner ring 801 is pivotably coupled . The inner ring 801 is coupled by respective first inner pivot joints 803 to the sleeve 105. To the inner ring 801, an outer ring 802 is coupling by respective outer pivot joints 804. The pivot axis of the inner pivot joint 803 is perpendicular to the pivot axis of the outer pivot joint 804.

The wing arrangement 110 (i.e. the first wing 111 and the second wing 112) is coupled to the outer ring 802. Hence, the coupling device 120 generates a Cardanian support. In other words, the wing arrangement 110 is gimbal- mounted and universal-mounted, respectively, to the aircraft fuselage 101.

Fig. 9 shows a further exemplary embodiment of the present invention. The aircraft comprises the fuselage 101 with a fuselage axis 102. The coupling device 120 comprises the sleeve 105. To the sleeve 105, bending sections 901 of the coupling device 120 are attached . At the end of the bending sections 901, the respective wings 111, 112 are attached . The bending section 901 may be formed integrally with the respective wings 111, 112, for example. The bending section 901 may be made of an elastomeric material, such that the wings 111, 112 may be movable to the fuselage nose 103 and to the fuselage tail 104, respectively.

It should be noted that the term "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined . It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims. List of Reference Signs:

100 aircraft 321 first hinge part

101 fuselage 322 second hinge part

102 fuselage axis, rotary axis

103 fuselage nose 501 rod

104 fuselage tail

105 sleeve 601 first fixing element

106 tail wing 602 second fixing element

603 chord line

110 wing arrangement 604 flowing direction of air

111 first wing 605 guiding slot

112 second wing 606 sliding direction of sleeve

113 first longitudinal wing axis 607 elongated through hole

114 second longitudinal wing axis

115 hollow root section 711 further first wing

712 further second wing

120 coupling device

121 hinge 801 inner ring

122 spring 802 outer ring

803 inner pivot joint

130 propulsion unit 804 outer pivot joint

805 coupling base

211 leading edge

212 trailing edge 901 bending section

Ff spring force

Fc centrifugal force

Claims

Claims:

1. Aircraft (100) for vertical take-off and landing, the aircraft (100) comprising

a fuselage (101) comprising a fuselage nose (103) and a fuselage tail (104),

a wing arrangement (110) comprising a longitudinal wing axis, and

a coupling device (120) which couples the wing arrangement (110) to the fuselage (101),

such that the wing arrangement (110), in a fixed-wing flight mode, does not rotate around the fuselage (101), and

such that the wing arrangement (110), in a hover flight mode, is tilted around the longitudinal wing axis with respect to its orientation in the fixed-wing flight mode and that the wing arrangement (110) rotates around the fuselage (101), and

wherein the wing arrangement (110) is coupled to the coupling device (120) such that in the hover flight mode a wing tip of the wing arrangement (110) is movable in a direction to the fuselage nose (103) or to the fuselage tail (104).

2. Aircraft (100) according to claim 1,

wherein the coupling device (120) comprises a bending section (901) which is located between the wing arrangement (110) and the fuselage (101) such that, in the hover flight mode, a wing tip of the wing arrangement (110) is movable in a direction to the fuselage nose (103) or to the fuselage tail (104).

3. Aircraft (100) according to claim 2,

wherein the bending section (901) comprises an elastomeric material.

4. Aircraft (100) according to one of the claims 1 to 3,

wherein the coupling device (120) comprises a hinge (121) which couples the wing arrangement (110) to the fuselage (101).

5. Aircraft (100) according to claim 4,

wherein the hinge (121) comprises a flapping hinge or an universal joint.

6. Aircraft (100) according to claim 4 or 5,

wherein the wing arrangement (110) comprises a hollow root section (115),

wherein the hinge (121) is slidably coupled within the hollow root section (115) such that the hinge (121) is slidable along the longitudinal wing axis between a locking position and a pivoting position,

wherein, in the locking position, the hinge (121) is located inside the hollow root section (115) such that a pivoting of the wing arrangement (110) is prevented, and

wherein, in the pivoting position, the hinge (121) is located outside the root section for allowing a pivoting of the wing arrangement (110).

7. Aircraft (100) according to claim 6,

wherein the coupling device (120) comprises a spring (122) which is coupled to the hinge (121) such that a spring force (Ff) of the spring (122) pretensions the hinge (121) to the locking position.

8. Aircraft (100) according to one of the claims 1 to 7, wherein the coupling device (120) comprises an inner ring (801) and an outer ring (802) which surrounds the inner ring (801),

wherein the inner ring (801) is coupled to the fuselage (101) by an inner pivot joint (803) such that the inner ring (801) is pivotable around an inner pivot axis,

wherein the outer ring (802) is coupled to the inner ring (801) by an outer pivot joint (804) such that the outer ring (802) is pivotable around an outer pivot axis,

wherein the inner pivot joint (803) and the outer pivot joint (804) are arranged with respect to each other such that the inner pivot axis and the outer pivot axis are orientated perpendicular with respect to each other.

9. Aircraft (100) according to one of the claims 1 to 8,

wherein the wing arrangement (110) comprises a first wing (111) and a second wing (112),

wherein the longitudinal wing axis is split in a first longitudinal wing axis

(113) and a second longitudinal wing axis (114),

wherein the first wing (111) extends along the first longitudinal wing axis (113) from the fuselage (101) and the second wing (112) extends along the second longitudinal wing axis (114) from the fuselage (101), wherein the first wing (111) is tiltable with a first rotary direction around the first longitudinal wing axis (113), and

wherein the second wing (112 is tiltable with a second rotational direction around the second longitudinal wing axis (114).

10. Aircraft (100) according to claim 9,

wherein the first rotational direction differs to the second

rotational direction.

11. Aircraft (100) according to one of the claims 1 to 10, further comprising

a propulsion unit (130) which is mounted to the wing arrangement (HO),

wherein the propulsion unit (130) comprises a turbo jet engine, a turbofan engine, a turboprop engine, a propfan engine and/or a propeller engine.

12. Method for operating an aircraft (100) for vertical take-off and landing, the method comprising

converting the aircraft (100) in a fixed-wing flight mode by arranging a wing arrangement (110) such that a fixed-wing flight is enabled, and

converting the aircraft (100) in a hover flight mode by tilting the wing arrangement (110) around a longitudinal wing axis and by rotating the wing arrangement (110) around a fuselage (101) of the aircraft (100),

wherein the fuselage (101) comprising a fuselage nose (103) and a fuselage tail (104),

wherein the wing arrangement (110) is coupled to the fuselage (101) by a coupling device (120),

wherein the wing arrangement (110) is coupled to the coupling device (120) such that in the hover flight mode a wing tip of the wing

arrangement (110) is movable in a direction to the fuselage nose (103) or to the fuselage tail (104).