Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
AIRCRAFT FOR VERTICAL TAKE-OFF AND LANDING WITH AN ENGINE AND A PROPELLER UNIT
Document Type and Number:
WIPO Patent Application WO/2014/177591
Kind Code:
A1
Abstract:
The present invention relates to an aircraft (100) for vertical take-off and landing. A wing arrangement (110) is coupled to a fuselage (101) such that the wing arrangement (110) is tiltable around a longitudinal wing axis of the wing arrangement (110) and such that the wing arrangement (110) is rotatable around the fuselage (101). The wing arrangement (110) is adapted in such a way that, in a fixed-wing flight mode, the wing arrangement (110) does not rotate around the fuselage (101). The wing arrangement (110) is further adapted in such a way that, in a hover flight mode, the wing arrangement (110) is tilted around the longitudinal wing axis with respect to its orientations in the fixed-wing flight mode and that the wing arrangement (110) rotates around the fuselage (101). An engine (120) comprising a drive shaft (121) with an engine rotary axis (122), wherein the engine (120) is coupled to the wing arrangement (110) in such a way that in the hover flight mode the engine rotary axis (122) comprise at least one component which is parallel to a rotary axis (102) of the wing arrangement (110) around the fuselage (101).

Inventors:
REITER JOHANNES (AT)
Application Number:
PCT/EP2014/058767
Publication Date:
November 06, 2014
Filing Date:
April 29, 2014
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
REITER JOHANNES (AT)
International Classes:
B64C29/00; B64C29/02
Domestic Patent References:
WO2012035153A12012-03-22
WO1998002350A11998-01-22
Foreign References:
US20120248259A12012-10-04
Attorney, Agent or Firm:
GALL, Ignaz (Haeusler Schindelmann Patentanwaltsgesellschaft mb, Leonrodstr. 58 München, DE)
Download PDF:
Claims:
Claims:

1. Aircraft (100) for vertical take-off and landing, the aircraft comprising a fuselage (101),

a wing arrangement (110),

wherein the wing arrangement (110) is coupled to the fuselage (101) such that the wing arrangement (110) is tiltable around a longitudinal wing axis of the wing arrangement (110) and such that the wing arrangement (110) is rotatable around the fuselage (101),

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

wherein the wing arrangement (110) is further adapted in such a way that, in a hover flight mode, the wing arrangement (110) is tilted around the

longitudinal wing axis with respect to its orientations in the fixed-wing flight mode and that the wing arrangement (110) rotates around the fuselage (101), an engine (120) comprising a drive shaft (121) with an engine rotary axis (122), wherein the engine (120) is coupled to the wing arrangement (110) in such a way that in the hover flight mode the engine rotary axis (122) comprise at least one component which is parallel to a rotary axis (102) of the wing arrangement (110) around the fuselage (101), and

a propeller unit (130) which is mounted to the wing arrangement (110), wherein the propeller unit (130) comprises a propeller shaft (131) which is coupled to the drive shaft (121) such that the engine (120) drives the propeller unit (130).

2. Aircraft (100) according to claim 1, further comprising

a gear (106) to which the drive shaft (121) of the engine (120) and the propeller shaft (131) of the propeller unit (130) are coupled such that a driving torque is transferrable from the drive shaft (121) to the propeller shaft (131) via the gear (106).

3. Aircraft (100) according to claim 2,

wherein the drive shaft (121) of the engine (120) and the propeller shaft (131) of the propeller unit (130) are coupled to the gear (106) in such a way that the engine rotary axis (122) and a propeller rotary axis (132) of the propeller shaft (131) comprise an angle (β) between each other.

4. Aircraft (100) according to claim 3,

wherein the angle (β) is in the hover flight mode between 60° and 120°, in particular a right angle.

5. Aircraft (100) according to claim 3 or 4,

wherein the angle (β) is in the fixed wing flight mode between -20° and +20°, in particular 0°.

6. Aircraft (100) according to one of the claim 3 to 5,

wherein the gear (106) is designed for adjusting the angle (β) between the engine rotary axis (122) and a propeller rotary axis (132) of the propeller shaft (131).

7. Aircraft (100) according to one of the claims 2 to 6,

wherein the gear (106) is a bevel gear.

8. Aircraft (100) according to one of the claims 1 to 7,

wherein the engine (120) is coupled to the wing arrangement (110) such that the engine (120) is tiltable together with the wing arrangement (110) around the longitudinal wing axis.

9. Aircraft (100) according to one of the claims 1 to 7, wherein the engine (120) is coupled to the wing arrangement (110) such that the wing arrangement (110) is tiltable around the longitudinal wing axis independently of the engine (120). 10. Aircraft (100) according to claim 9, further comprising

a sleeve (103) to which the wing arrangement (110) is coupled, wherein the sleeve (103) is rotatably mounted to the fuselage (101), wherein the wing arrangement (110) further comprises a support structure (401) which is mounted to the sleeve (103),

wherein the wing arrangement (110) is tiltable around the longitudinal wing axis relatively to the support structure (401), and

wherein the engine (120) is mounted to the support structure (401) such that the wing arrangement (110) is tiltable around the longitudinal wing axis independently of the engine (120).

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

wherein the engine (120) comprises a piston engine, turbo jet engine, a turbofan engine, a turboprop engine, a propfan engine and/or a propeller engine.

12. Aircraft (100) according to one of the claims 1 to 11,

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).

13. Aircraft (100) according to claim 12,

wherein the first rotational direction differs to the second rotational direction .

14. 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,

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 wing arrangement (110) is coupled to the fuselage (101), and driving the aircraft (100) by an engine (120) comprising a drive shaft

(121) with an engine rotary axis (122),

wherein the engine (120) is coupled to the wing arrangement (110) in such a way that in the hover flight mode the engine rotary axis (122) comprise at least one component which is parallel to a rotary axis (102) of the wing arrangement (110) around the fuselage (101),

wherein a propeller unit (130) is mounted to the wing arrangement, and wherein the propeller unit (130) comprises a propeller shaft (131) which is coupled to the drive shaft (121) such that the engine (120) drives the propeller unit (130).

Description:
Aircraft for vertical take-off and landing with an engine and a propeller unit

FIELD OF THE INVENTION The present invention relates to an aircraft for vertical take-off and landing comprising an engine and a propeller unit and to a method for operating an aircraft for vertical take-off and landing comprising an engine and a propeller unit.

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 where the wing arrangement rotates around the fuselage, so that the wing arrangement generates lifting forces for lifting the aircraft, different loads and load changes act onto the wings during the rotation of the wings. Furthermore, propulsion units are mounted to the wing arrangement for driving the wing arrangement around the fuselage. The propulsion unit comprises rotating masses e.g. the propeller or the driving shaft of the propulsion unit. The rotating masses which comprise a rotating axis that directs during rotation of the wing arrangement along a

circumferential direction around the fuselage generate, amongst others, a precession force. The faster the wing arrangement and the propulsion unit, respectively, rotates around the fuselage, the higher is the precession force which can negatively affect the structural stability of the wing arrangement.

OBJECT AND SUMMARY OF THE INVENTION

It may be an object of the present invention to provide an aircraft for vertical take-off and landing comprising a wing arrangement onto which a reduced precession force act darting a rotation of the wing arrangement around the fuselage.

This object may be solved by an aircraft for vertical take-off and landing and by a method for operating an aircraft for vertical take-off and landing according to the independent claims. According to a first aspect of the present invention, an aircraft for a vertical take-off and landing is presented . The aircraft comprises a fuselage and a wing arrangement. The wing arrangement is coupled to the fuselage such that the wing arrangement is tiltable around a longitudinal wing axis of the wing arrangement and such that the wing arrangement is rotatable around the fuselage. The wing arrangement is adapted in such a way that in a fixed wing flight mode, the wing arrangement does not rotate around the fuselage. The wing arrangement is further adapted in such a way that in a hover flight mode, the wing arrangement is tiltable 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.

The aircraft further comprises an engine comprising a drive shaft with an engine rotary axis, wherein the engine is coupled to the wing arrangement in such a way that in the hover flight mode, the engine rotary axis comprises at least one component which is parallel or almost parallel to a rotary axis of the wing arrangement around the fuselage. In particular, the engine rotary axis is (at least with one component) parallel to the rotary axis of the wing

arrangement around the fuselage.

Furthermore, the aircraft comprises a propeller unit which is mounted to the wing arrangement. The propeller unit comprises a propeller shaft which is coupled to the drive shaft such that the engine drives the propeller unit. According to a further aspect of the present invention, a method for operating the above-described aircraft for vertical take-off and landing is presented. According to the method, the aircraft is converted in the fixed wing flight mode by arranging a 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 the longitudinal wing axis and by rotating the wing arrangement around the fuselage of the aircraft. Furthermore, the aircraft is driven by an engine comprising a drive shaft with the engine rotary axis.

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) 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.

Furthermore, 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.

The engine comprises a piston engine, a turbojet engine, a turbofan engine, a turboprop engine, a prop fan engine and/or a propeller engine. Generally, the engine comprises a movable and rotatable mass. The rotatable mass is in particular the drive shaft of the engine. Furthermore, the engine may comprise a movable piston which conducts a piston stroke along a certain piston stroke direction. The engine generates a driving torque which is transmitted by the drive shaft. The drive shaft extends along the engine rotary axis. According to the present invention, the engine is arranged such that the engine rotary axis comprises at least in the hover flight mode at least one component which is parallel to the rotary axis (e.g. the fuselage axis) of the wing arrangement around the fuselage. Specifically, the engine rotary axis is in the hover flight mode parallel with rotary axes of the wing arrangement around the fuselage. The propeller unit comprises propellers which rotate through the air such that thrust along a driving direction is generated . In particular, the propeller unit comprises a propeller shaft which is coupled to the drive shaft for transmitting the driving torque from the drive shaft to the propeller shaft. The propeller shaft and the propeller rotary axis, respectively, may be non-parallel with respect to the engine rotary axis of the drive shaft in the hover flight mode. For example, a gear, such as a bevel gear, may be coupled between the propeller shaft and the drive shaft for transmitting the drive torque.

The engine and the propeller unit are mounted to the wing arrangement and thus rotate in the hover flight mode around the fuselage.

The rotation of the drive shaft around the engine rotary axis and the rotation of the propellers of the propeller unit and the propeller shaft define rotating masses. The wing arrangement and thus the engine and the propeller unit run during rotation around the fuselage along a circumferential path around the rotary axis. In particular, the mass of the propeller and the mass of the propeller shaft try to run along a linear and tangential direction with respect to the circumferential path. Due to the rotation of the wing arrangement around the rotary axis, the propeller unit and the engine are forced to rotate around the rotary axis around the fuselage along the circumferential path, so that a constraint force, which is directed radially to the rotary axis, forces the propeller unit and the engine unit to leave its desired longitudinal and tangential direction and hence forces the propeller unit and the engine unit to move along the circumferential path around the rotary axis around the fuselage. The constraint force acts on the rotating mass, such as the propeller shaft which rotates around the propeller rotary axis and causes a precession force. The precession force acts along a direction which is approximately perpendicular (90°) shifted with respect to the constraint force along the tangential direction of the rotating mass around the propeller rotary axis (i.e. a rotary axis which directs along the tangential direction with respect to the circumferential path).

The precession force is dependent on the rotational speed of the rotating mass and in particular on the alignment of the respective mass rotary axis of the rotating mass. Specifically only rotary masses which comprise a mass rotary axis that is tangentially with respect to the circumferential path generate a part of the precession force.

Hence, by the approach of the present invention, because the orientation of the engine rotary axis of the drive shaft is arranged parallel (or at least with one component parallel) to the rotary axis of the wing arrangement around the fuselage, the rotating mass, such as the drive shaft, of the engine does not generate or reduce only a small amount of precession force. Only the propeller unit, which propellers need a propeller shaft and a respective propeller rotary axis along a tangential with respect to the circumferential path, generate a precession force. In other words, a rotating mass which comprises a rotary axis that is directed along a tangential direction of the circumferential path around the fuselage cause a precession force.

Hence, by the approach of the present invention, because the engine rotary axis is orientated (at least with one component) parallel to the rotary axis, the mass of the engine generates none or a marginal precession force. Hence, by this arrangement, the precession force is reduced such that a reduced amount of disturbing loads acts on the wing arrangement during the hover flight mode. Hence, a more stable aircraft is provided . In the hover flight mode, the orientation of the drive shaft differs to the orientation of the propeller shaft. As described above, according to an exemplary embodiment of the present invention, the aircraft comprises a gear to which the drive shaft of the engine and the propeller shaft of the propeller unit are coupled such that a driving torque is transferable from the drive shaft to the propeller shaft via the gear. Hence, the gear may be for example a universal joint, a cardan shaft, an angular gear or a bevel gear, respectively. Hence, in the hover flight mode, the propeller shaft and its propeller rotary axis differ to the drive shaft and its respective engine rotary axis. Additionally it is to say that the precession force is also dependent on the weight, the rotational speed of the wing arrangement around the rotary axis around the fuselage and the center of gravity of the rotating mass.

According to a further exemplary embodiment, the drive shaft of the engine and the propeller shaft of the propeller unit are coupled to the gear in such a way that the engine rotary axis and a propeller rotary axis of the propeller shaft comprise an angle between each other.

In particular, according to an exemplary embodiment, the angle is in the hover flight mode between approximately 60° (degree) and approximately 120°, in particular approximately a right angle.

According to a further exemplary embodiment, the angle is in a fixed wing flight mode between approximately -20° and approximately +20°, in particular approximately 0°. Hence, in the fixed wing flight mode, the propeller rotary axis is parallel with the engine rotary axis. Because in the fixed wing flight mode the wing arrangement does not rotate around the fuselage and has no relative motion to the fuselage, the orientation of the engine rotary axis is not relevant because no precession force is generated . According to a further exemplary embodiment, the gear is designed for adjusting the angle between the engine rotary axis and the propeller rotary axis of the propeller shaft. For example, the engine and his engine rotary axis are independently pivotable with respect to the propeller unit. Furthermore, the engine and his engine rotary axis are independently pivotable with respect to the rotary axis of the wing arrangement around the fuselage. The gear is thereby adapted to adjust the gear angel between the drive shaft and the propeller shaft. Hence, by controlling the alignment of the engine rotary axis with respect to the rotary axis of the wing arrangement, the precession force acting onto the wing arrangement may be controlled and adjusted . For example, if the engine is pivoted such that an angle between the engine rotary axis of the rotor shaft and the rotary axis of the wing arrangement around the fuselage is increased and an angle between the engine rotary axis of the rotor shaft and the tangential direction of the circumferential path is reduced, the precession force may be controllably increased .

According to a further exemplary embodiment of the present invention, the engine is coupled to the wing arrangement such that the engine is tiltable together with the wing arrangement around the longitudinal wing axis. Hence, by the present exemplary embodiment, the engine rotary shaft is spatially fixed with respect to the propeller driving shaft. According to a further exemplary embodiment, the engine is coupled to the wing arrangement, such that the wing arrangement is tiltable around the longitudinal wing axis independently of the engine. For example, the engine is rotatable relatively to the propeller by a servomotor, a hydraulic, a pneumatic or an electrical motor with respect to the propeller unit. For example, in the hover flight mode, the orientation of the drive shaft and the engine, respectively, may be individually adjusted by adjusting means, such as the servomotor.

According to a further exemplary embodiment, the aircraft comprises a sleeve to which the wing arrangement is coupled. The sleeve is rotatably mounted to the fuselage. The wing arrangement further comprises a support structure, such as a supporting frame, which is mounted to the sleeve and hence rotates together with a sleeve and the wing arrangement around the fuselage in the hover flight mode. The wing arrangement is tiltable around the longitudinal wing axis relatively to the support structure. In other words, the support structure is non-rotatably fixed to the sleeve and does not rotate together with the wing arrangement around the longitudinal wing axis.

The engine is mounted to the support structure, such that the wing

arrangement is tiltable around the longitudinal wing axis independently with respect to the engine.

In the following an exemplary coupling mechanism of the wing arrangement to the fuselage is described . The sleeve surrounds the fuselage. The sleeve is slidable along the fuselage and rotatable around the fuselage. The wing arrangement is fixed by a second fixing element, such as a fixing bolt, to the fuselage. The second fixing element is rotatable around the fuselage but is not coupled to the sleeve. The wing arrangement is tiltable around the second fixing element. Furthermore, a first fixing element couples the wing

arrangement to the sleeve. The first fixing element is spaced apart from the second fixing element and is relatively movable with respect to the fuselage.

Furthermore, the sleeve comprises an elongated through-hole through which the second fixing element is guided. If the sleeve moves along a sliding direction along the fuselage, the sleeve is not blocked by the second fixing element. During converting of the aircraft between the fixed wing flight mode and the hoover flight mode, the sleeve is moved along the fuselage axis. Thereby, the sleeve moves the first fixing element along the fuselage which causes the wing arrangement to rotate around the second fixing element, which is spatially fixed to the fuselage. Thereby, the angle of attack which defines an angle between the cord line of the wing arrangement and the flowing direction of the air is adjustable.

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 exemplary embodiment of an aircraft for vertical take-off and landing according to the present invention;

Fig. 2 shows a schematical view of a wing arrangement comprising an engine and the propeller unit according to an exemplary embodiment of the present invention;

Fig. 3 shows a schematical side view of an aircraft according to an exemplary embodiment of the present invention; and

Fig. 4 shows a schematical view of an aircraft comprising an engine support structure 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 shows an aircraft 100 for vertical take-off and landing. The aircraft 100 comprises a fuselage 101 and a wing arrangement 110. The wing arrangement 110 is coupled to the fuselage 101 such that the wing arrangement 110 is tiltable around a longitudinal wing axis of the wing arrangement 110 and such that the wing arrangement 110 is rotatable around the fuselage 101. The wing arrangement 110 is adapted in such a way that, in a fixed wing flight mode, the wing arrangement does not rotate around the fuselage. In the fixed wing flight mode, the aircraft 100 flies through the air, wherein the wing arrangement 110 generates lift due to the speed of the aircraft 100 through the air.

Fig. 1 shows the aircraft 100 in a hover flight mode. The wing arrangement 110 is adapted in such a way that in the hover flight mode, the wing

arrangement 110 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 (see arrow in Fig . 1). The wing arrangement 110 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. Each wing 111, 112 comprise a respective leading edge 115 and trailing edge 116.

A sleeve 103 is rotatably mounted to the fuselage 101. The wing arrangement 110 is mounted to the sleeve 103 such that in the hover flight mode the sleeve 103 rotates together with the wing arrangement 110 around the fuselage 101.

Furthermore, a respective engine 120 is coupled to each of the first wing 111 and the second wing 112. The engine 120 comprises a drive shaft 121 with an engine rotary axis 122. The engine 120 is coupled to the respective wings 111, 112 in such a way that in the hover flight mode the engine rotary axis 122 comprises at least one component which is parallel to a rotary axis 102 of the wing arrangement 110 around the fuselage 101. In Fig . 1, the rotary axis 102 is parallel to a fuselage axis. In other exemplary embodiments of the present invention, the rotary axis 102 may comprise an angle to the fuselage axis. Furthermore, the engine rotary axis 110 comprises at least one component which is parallel to the rotary axis 102 of the wing arrangement 110. Specifically, as shown in Fig . 1, the engine rotary axis 122 is parallel to the rotary axis 102.

Furthermore, respective propeller units 130 are mounted to respective wings 111, 112. Each propeller unit 130 comprises a propeller shaft 131 which is coupled to the respective drive shaft 121 such that the engine 120 drives the propeller unit 130.

In the hover flight mode as shown in Fig. 1, the propeller unit 130 rotates along a circumferential path around the rotary axis 102.

The rotation of the drive shaft 121 around the engine rotary axis 122 and the rotation of the propeller shaft 131 around the propeller rotary axis 132 define rotating masses. The wing arrangement 110 and thus the engine 120 and the propeller unit 130 run during rotation around the fuselage along a

circumferential path 117 around the rotary axis 102. In particular, the mass of the propeller shaft 131 and its propellers try to run along a linear and tangential direction with respect to the circumferential path 117. Due to the rotation of the wing arrangement 110 around the rotary axis 102, the propeller unit 130 and the engine 120 are forced to rotate around the rotary axis 102 around the fuselage 101, so that a constraint force Fc, which is directed radially to the rotary axis 102, forces the propeller unit 130 and the engine 120 to leave its desired longitudinal and tangential direction and hence forces the propeller unit 130 and the engine 120 to move along the

circumferential path 117 around the rotary axis 102. The constraint force Fc acts on the rotating mass, such as the propeller shaft 131 which rotates around the propeller rotary axis 132 and causes a precession force Fp. The precession force Fp acts along a direction which is approximately

perpendicular (90°) shifted with respect to the constraint force Fc along the tangential direction of the rotating mass around the propeller rotary axis 132 (i.e. a rotary axis which directs along the tangential direction with respect to the circumferential path 117).

The precession force Fc is dependent on the rotational speed of the rotating mass and in particular on the alignment of the respective mass rotary axis of the rotating mass. Specifically, only rotary masses which comprise a mass rotary axis that is tangentially with respect to the circumferential path 117 generate a part of the precession force.

Hence, because the orientation of the engine rotary axis 122 of the drive shaft 121 is arranged parallel (or at least with one component parallel) to the rotary axis 102 of the wing arrangement 110 around the fuselage 101, the rotating mass, such as the drive shaft, of the engine does not generate or reduce only a small amount of precession force Fp. Only the propeller unit 130, which propellers need a propeller shaft 131 and a respective propeller rotary axis 132 along a tangential with respect to the circumferential path 117, generate a precession force.

Hence, due to the rotating masses of the propeller unit 130, a precession force is generated . On the other side, because the rotating masses of the engine 120, in particular because the drive shaft 121 as a part of the rotating mass is aligned with its engine rotary axis 122 parallel to the rotary axis 102, the rotating mass of the drive shaft 121 does not generate a part of the

precession force Fp. Hence, the overall precession force Fp is reduced by the arrangement of the drive shaft 121 with respect to the propeller shaft 131 as shown in Fig. 1. In order to couple the differently orientated drive shaft 121 and the propeller shaft 131, a gear 106 is arranged . The gear 106 may be designed such as a universal joint. Furthermore, the gear 106 may be designed as a bevel gear or angled gear.

In particular, as shown in Fig . 1, the drive shaft 121 of the engine 120 and the propeller shaft 131 of the propeller unit 130 are coupled to the gear 106 in such a way that the engine rotary axis 122 and the propeller rotary axis 132 of the propeller shaft 131 comprise an angle β between each other. In the exemplary embodiment in Fig. 1, the angle β is approximately perpendicular.

In a fixed wing flight mode (not shown), the first wing 111 is tiltable with a first rotary direction around the first longitudinal wing axis and the second wing 112 is tiltable with a second rotational direction around the second longitudinal wing axis 114. The first rotational direction differs to the second rotational direction. Hence, both propulsion units 130 of the respective wings 111, 112 generate thrust in order to drive the aircraft 100 through the air. By the speed through the air of the aircraft 100, lift is generated by the

respective wings 111, 112. In the fixed wing flight mode, the angle β may be around +/-20 0 , in particular 0°, depending on an angle of attack a between the respective wings 111, 112 and the direction of air 301 (see Fig. 3).

In the exemplary embodiment shown in Fig. 1, the propeller unit 130 is spatially fixed to the respective wings 111, 112 such that the engine 120 rotates together with the respective wings 111, 112 around the respective longitudinal wing axis 113, 114.

Furthermore, in the tail section of the fuselage 101, a further propulsion unit 104, such as a jet engine, may be installed . Furthermore, at the tail section of the fuselage 101, tail wings 105 may be attached which provide for example control surfaces for stabilizing the aircraft 100 during the flight. Fig. 2 shows a more detailed schematical of the engine 120 and the propeller unit 130 which are mounted to the first wing 111. As shown in Fig. 2, the gear 106 may be a bevel gear in order to couple the propeller shaft 131 with the drive shaft 121 which are approximately perpendicular arranged with respect to each other.

Furthermore, the engine 120 may be a piston engine which comprises a piston 123. The piston is movable longitudinally along a piston stroke direction 124. The engine 120 may be designed in such a way, that the piston stroke direction 124 is approximately parallel to the longitudinal wing axis 113 such that the centrifugal forces which are generated because of the rotation of the wing arrangement 110 around the fuselage 101 support a proper fuel distribution inside the cylinder of the engine 120.

Fig. 3 shows a side view of the aircraft 100. As shown in Fig . 3, the wing arrangement 110 is fixed by a coupling section 302, such as a coupling pin or a wing spar, to the sleeve 103 which is rotatably mounted to the fuselage 101. The aircraft section of the aircraft 100 as shown in Fig . 3 is shown in the hover flight mode.

In particular, the wing arrangement 110 comprises a cord line 303 which connects the leading edge 115 with the trailing edge 116. The propeller rotary axis 132 may be parallel to the cord line 303. An angle of attack a is defined between the cord line 303 and a direction of air 301 which streams again the leading edge 115.

The angle β between the propeller rotary axis 132 and the engine rotary axis 122 may be approximately 90°. Furthermore, the gear 106 is shown which couples the propeller shaft 131 with the drive shaft 121. The piston 123 of the engine 120 comprises a piston stroke direction 124. In order to use the centrifugal force acting on the rotating wing arrangement 110 for the fuel distribution inside a cylinder of the engine 120, the piston 123 may be arranged inside the engine 120 in such a way that the piston stroke direction 124 is aligned parallel with the longitudinal wing axis of the wing arrangement 110.

Fig. 4 shows a further exemplary embodiment. The aircraft 100 is shown in the hover flight mode wherein the wing arrangement 110, i.e. the respective first wing 111 and the respective second wing 112 rotate around the rotary axis 102. The first wing 111 and the second wing 112 are mounted to the sleeve 103 which is rotatably fixed to the fuselage 101.

The sleeve 103 comprises a support structure 401, such as a framework. The engine 120 is mounted to the support structure 401 such that the wing arrangement 110 is tiltable around the longitudinal wing axis 113, 114 independently of the engine 120. For sake of clarity, only the engine 120 at the first wing 111 is shown.

Hence, if the first wing 111 is tilted around the longitudinal wing axis 113 between the fixed wing flight mode and the hover flight mode, the propeller unit 130 and its propeller shaft 131 rotates together with the first wing 111, whereas the engine 120 with its driving shaft 121 does not rotate around the first longitudinal wing axis 113. However, the engine 120 rotates together with the sleeve 103 around the rotary axis 102. The propeller unit 130 is tiltable together with the wing arrangement 110 around the first longitudinal wing axis 113.

Hence, although the first wing 111 is tilted around the first longitudinal wing axis 113, the drive shaft 121 and its engine rotary axis 122 is approximately parallel to the rotary axis 102 such that no precession force Fp is generated by the rotating of the drive shaft 121. The drive shaft 121 and/or the propeller shaft 131 may be adjustable in its length, such that a proper force transmission between both shafts 121, 131 is provided if the first wing 111 rotates around the longitudinal wing axis 113. Depending of the angle of attack a of the first wing 111, the angle β between the propeller rotary axis 132 and the engine rotary axis 122 may be between 60° and 120° in the hover flight mode and between -20° and +20° in the fixed wing flight mode. Furthermore, as shown in Fig . 4, the engine 120 is arranged to the first wing 111 in such a way, that the piston 123 in a cylinder of the engine 120 comprises a piston stroke direction 124 which is aligned along a radial direction to the rotary axis 102 and/or parallel with the first longitudinal wing axis 113. Hence, the centrifugal force which acts on the engine 120 may provide a proper fuel distribution of the fuel inside the cylinder of the engine 120.

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.

Reference Signs:

100 aircraft engine support structure

101 fuselage

102 fuselage axis, rotary axis angle of attack

103 sleeve angle between propeller rotary

104 further propulsion unit axis and engine rotary axis

105 tail wing constraint force

106 gear precession force

110 wing arrangement

111 first wing

112 second wing

113 first longitudinal wing axis

114 second longitudinal wing axis

115 leading edge

116 trailing edge

117 circumferential path

120 engine

121 drive shaft

122 engine rotary axis

123 piston

124 piston stroke direction

130 propeller unit

131 propeller shaft

132 propeller rotary axis

301 direction of air

302 coupling section

303 chord line