WO2019034765A1

WO2019034765A1 - Vertical takeoff aircraft

Info

Publication number: WO2019034765A1
Application number: PCT/EP2018/072299
Authority: WO
Inventors: Paul Schreiber
Original assignee: Paul Schreiber
Priority date: 2017-08-18
Filing date: 2018-08-17
Publication date: 2019-02-21
Also published as: DE102017118965A1

Abstract

The invention relates to a vertical takeoff aircraft (1), preferably an unmanned aerial vehicle (UAV), drone and/or unmanned aerial system (UAS), comprising: a rigid wing (5) which is oriented substantially horizontally both when hovering and in horizontal flight and allows aerodynamic horizontal flight, and, with regard to the centre of mass (20) of the aircraft (1), at least one rear adjustable drive (11), as seen in the direction of horizontal flight, comprising a rear motor (12) and a rear propeller (13) driven by the rear motor (12), and at least one front adjustable drive (16), as seen in the direction of horizontal flight, comprising a front motor (17) and a propeller (18) driven by the front motor (17), wherein the motors (12, 17) are preferably electric motors, and wherein at least some of the drives (11, 16) are pivotable by means in each case of a pivoting mechanism between a vertical takeoff position for hovering and a horizontal flight position for horizontal or cruising flight. The invention is characterized in that the at least one rear or front drive (11, 16) is arranged and designed such that it applies more than 50% of the hovering thrust required for the aircraft (1) to hover and less than 50% of the propulsion force in horizontal flight, while the at least one front or rear drive (16, 11) is arranged and configured such that it applies less than 50% of the hovering thrust required for the aircraft (1) to hover and more than 50% of the propulsion force in horizontal flight.

Description

Vertically launching aircraft

The present invention relates to a vertically take-off aircraft, preferably unmanned aerial vehicle (UAV), drone and / or unmanned aerial vehicle (UAS), according to the preamble of claim 1. The aircraft starts with a substantially horizontally oriented rigid wing; after reaching the intended altitude it flies without turning, tilting or pivoting of the aircraft fuselage in the horizontal direction.

Such an aircraft is known from EP 2 776 315 B1. In this four propellers (called rotors there) are arranged in an H-shaped arrangement with respect to the longitudinal axis of the aircraft on the wing. There are therefore two propellers in front and two propellers behind the wing. The four propellers are all pivoted upwards in the vertical start position, i. their motor axes run substantially in the vertical direction. In horizontal flight, however, the propellers are pivoted about 90 ° forward or backward. In this flight position, the motor axes are substantially parallel to the wing plane and the propellers, which all provide for the propulsion in horizontal flight are accordingly arranged perpendicular to the wing.

The center of gravity of the known aircraft coincides both at take-off and during landing and in hover-near conditions with the lift center of gravity of the four propellers. Here, the distances of the motor or propeller axes are evenly distributed to the center of gravity, so that all drives carry about the same load.

A disadvantage of the known aircraft is that its power output and thus in particular its range still have potential for optimization. It is an object of the present invention to provide an aircraft with improved flight and performance characteristics.

This object is solved by the features of claim 1.

According to the invention it is provided that the rear or the front drives are arranged and designed to provide more than 50% of the hover thrust and less than 50% of the propulsive force in horizontal flight. In contrast, the front and the rear drives to provide less than 50% of the hover thrust and more than 50% of the driving force in horizontal flight are arranged and designed. The core of the invention lies in the asymmetric task distribution of the front and rear drives. The two drive groups - on the one hand the front or the other and / or the rear drives - take respectively different main tasks, namely on the one hand, the hover mode and on the other the travel or horizontal flight mode. As a result of this task focusing, each of the two drive groups-on the one hand the rear drives and on the other hand the front drives-can be arranged and designed with regard to their respective primary task.

If, in the context of the present description, the term "front drives" or "rear drives" is intended to encompass embodiments with only one front drive or one rear drive.

The advantage of the embodiment according to the invention is therefore that the front and the rear drives can each be optimally designed for their actual tasks. The one - either the rear or the front - drives are predominantly for levitation, so in particular the starting and landing, responsible, while the other - so either the front or the rear drives - predominantly for propulsion to care. This specialization allows both better hovering and faster and / or more efficient cruise in the horizontal direction.

The design of the drives is particularly preferably determined by the diameter of the associated propeller and / or by their pitch. An aircraft needs in horizontal flight only relatively little thrust to keep the altitude. The thrust is generated at high flow velocity on the propeller. On the other hand, when hovering, i. especially when starting and landing, a much higher thrust is needed. The thrust is, for example, by a factor of 15 to 20 higher than in horizontal flight, although the flow velocity is very small.

Accordingly, a propeller designed primarily for horizontal flight requires a much smaller ratio of diameter per pitch or significantly smaller quotients of pitch divided by pitch than a propeller designed primarily for propulsion while levitating. This quotient of the latter propeller or propellers is preferably greater by at least 25%, for example by at least 50% greater, more preferably greater by more than 100%, for example by 150% or 200% greater than in the case of the former or the propellers mentioned.

In particular, an embodiment with two rear and two front drives has proven to be advantageous because with these four drives the desired optimized flight characteristics can be achieved at a low price, ease of use and low susceptibility to interference.

According to two alternatives, two rear drives and one front drive, or one rear drive and two front drives are provided. Even with such constellations, it is in principle possible to realize the inventive asymmetric distribution of applying the hover thrust and the propulsive force in Horizontalf lug. More preferably, the center of mass of the aircraft is located off-center with respect to the front and rear propellers.

Hereby, the various main functions of the front and rear drives, ie on the one hand the hovering (in particular the takeoff and landing) and on the other hand the cruising, can be further optimized.

In an embodiment which is advantageous in this respect, the center of mass of the aircraft is arranged closer to those drives which apply the higher hovering thrust. Preferably, the corresponding lever arms are at least 5%, and more preferably at least 10%, for example more than 15% or 20% or even more than 25% or 30%, shorter than the lever arms of those drives, which the lower (to no) hover force. Due to the shorter lever arm in relation to the main responsible for the hover drives they can raise a larger mass fraction. For example, if these are the rear drives, the center of gravity is located closer to the rear drives than the front drives. Shifting the center of mass to the rear propellers raises more than 50% of the mass from the rear drives, relieving the front drives. These can therefore be better for their task, namely the propulsion in horizontal flight, designed. Thus, the hover thrust force can be concentrated on the rear drives, since the front drives contribute to this only a relatively smaller part. The same applies to the opposite case, namely when the front drives lift the majority of the mass of the aircraft, while the rear drives predominantly (or completely) take over the majority of the propulsion.

The greater the shift of the center of mass to the majority of the hover thrust load-absorbing drives, the more mass can be moved to these drives and the further the other drives can be optimized for horizontal flight. Here it is It is especially preferred if the drives responsible for the majority of the driving force contribute to hovering only to a small extent, for example between 10% and 20%.

It should be noted that it is also possible in principle to design the front (or the rear) drives for horizontal flight without the above-described displacement of the center of mass, and the rear (or the front) for hovering. In this case, the rear and front drives would have to be designed differently with respect to their respective main task (hovering or level flight). However, in this case, the disadvantage remains that the drive optimized for horizontal flight must continue to generate a large proportion of the hovering thrust and thus suffers the hovering efficiency. So it would have to be compromised in the design of the drives.

It has been found to be advantageous if the rear or front drives are designed to provide more than 55%, preferably more than 60% of the hover thrust, while the front and rear drives provide less than 45%, preferably less than 40%, the hover thrust force are designed. This is equivalent to the rear or front drives lifting more than 55%, preferably more than 60% of the mass, and the front and rear drives less than 45%, preferably less than 40% of the mass. Accordingly, in certain embodiments, greater asymmetry in the distribution of hovering traction forces is advantageous.

This asymmetry may also be increased to such an extent that the rear or front drives are designed to provide more than 65%, preferably more than 70% of the hover thrust (ie lifting more than 65% or 70% of the mass), while the front and the rear drives to provide less than 35%, preferably less than 30% designed for hover thrust (ie lifting less than 35% or 30% of mass).

Embodiments of the aircraft according to the invention are also possible in which the one or more of the rear or front drives are designed to provide more than 80%, for example more than 90%, of the hover thrust while the one or more front or rear drives are providing it less than 20%, for example less than 10%, of hovering thrust. In extreme cases, even the entire hovering performance can be reduced by e.g. the rear or the front drives are provided, while then serve the front and rear drives only for stabilization.

According to a preferred embodiment of the aircraft according to the invention, the front and rear drives contribute both to providing the hovering thrust force necessary for hovering the aircraft and to providing propulsive force in horizontal flight.

In an alternative to the aircraft according to the invention, the front and rear drives also contribute to providing the hovering thrust necessary for hovering the aircraft. However, then only a part of these drives takes the propulsive force in horizontal flight, while the other part of the drives is switched off.

Preferably, all drives are pivotable by means of a respective pivoting mechanism between a vertical start position for the hover and a horizontal flight position for the cruise. Thus, all drives on the one hand for launching and landing, in general levitation, can be used (albeit differently designed), on the other hand, they are used for propulsion in cruise or, if they are not used for this purpose, be pivoted into an aerodynamic position , According to an alternative, only those drives by means of a respective pivot mechanism between a vertical start position for the

Hover and a horizontal flight position for travel or horizontal flight pivotable, which contribute to propulsion in horizontal flight.

Preferably, all drives are arranged on the wing. This arrangement is relatively easy to implement. In addition, several rear and several front drives can be distributed favorably in the transverse direction of the aircraft. Four drives offer an X- or H-shaped arrangement.

Preferably, the rear propeller in the hover down and pivot for the horizontal flight backwards against the flight direction, preferably by 75 ° to 105 °, more preferably by 85 ° to 95 °. Furthermore, it is advantageous if the front propeller in hovering upward and pivot for horizontal flight by 90 ° forward in the direction of flight, preferably by 75 ° to 105 °, more preferably by 85 ° to 95 °. The constellation is also possible that in hover both the front and the rear propeller are pivoted upwards, while the rear in horizontal flight are pivoted to the rear and the front to the front.

Particularly preferably, the rear or front propeller for horizontal flight are hinged or collapsible. This design helps to improve aerodynamics and acoustics in cruising. In this way, the speed and range of the aircraft is increased with less noise.

Preferably, those propellers are hinged, the associated drives are arranged and designed so that they provide more than 50% of the hover thrust. In a corresponding embodiment, it is particularly advantageous if the rear propeller are formed hinged against the direction of flight in horizontal flight, preferably due to the action of wind forces or the wind.

Particularly preferably, a control device for controlling the motors is provided in such a way that the aircraft is automatically stable in a stable hovering flight. The control for the drives, the propeller, the ailerons, etc. by means of the control device can be done manually, semi-automatically or automatically. In particular, the transition between the two Flugzugzustanden (preferably hovering with front and rear drives - horizontal flies only with preferably the front drives) can be realized either manually or automatically. Then, in particular, the propeller speeds are preferably adapted.

The invention will be explained in more detail below with reference to figures. Show it:

Fig. 1 is a perspective plan view of an inventive

Aircraft in limbo;

FIG. 2 shows the aircraft according to FIG. 1 in the suspended state, seen from the side; FIG.

Fig. 3 is a perspective plan view of the aircraft of Figures 1 and 2, now in horizontal flight.

Fig. 4 shows the aircraft of FIG. 3 in horizontal flight, from the

Side view; Fig. 5-7 are side views of only the wing and the attached gondolas of the aircraft according to Figures 1 - 4, each with different pivot positions of the drives.

8 is a plan view of the aircraft of FIGS. 1-7 with the center of mass drawn in, and FIG

Fig. 9 is a plan view of a front and a rear drive, connected by the respective associated gondolas, with marked axis of gravity.

In Figs. 1 and 2, an aircraft according to the invention is shown in a suspended state in a perspective plan view and in side view. The aircraft 1 has an elongated aircraft fuselage 2 with a tail 3 and a nose 4. In the illustrated embodiment, the aircraft fuselage 2 is formed in one piece; but it can also consist of several parts, for example, two in the longitudinal direction of the aircraft 1 side by side extending body parts. The rear part of the fuselage 2 is designed as a tail boom 6 with a relatively small diameter, at the end facing the rear 3, a V-tail 7 is arranged with elevators 7a.

In the front region of the aircraft 1, a wing 5 extending transversely to the aircraft fuselage is arranged. The wing 5, starting from the longitudinal axis of the aircraft 1, initially has a forward pointing negative wing sweep, while subsequently having a rearward facing positive wing sweep towards the wing tips. At the trailing edge of the wing 5 ailerons 8a, 8b are provided. Furthermore, 4 runners 9a, 9b are provided below each wing half and below the nose. These three runners 9a, 9b form the landing gear of the aircraft 1. On the wing 5 also two pairs of drives 1 1, 16 are arranged symmetrically to the longitudinal axis of the aircraft 1. Each of the two wing halves in this case has a rear drive 1 1 and a front drive 16, wherein two of these drives 1 1, 16 are in the longitudinal direction of the aircraft 1 in a row. The drives 1 1, 16 are each arranged on a rear or front nacelle 10 and 15, wherein the gondolas 10, 15 merge into each other, that are integrally formed. The rear gondolas 10 are slightly curved upward in the direction of the stern 3, while the front gondolas 15 extend substantially horizontally.

At the free end of each rear nacelle 10 is a rear drive 1 1

pivotally arranged by means of a pivot joint 14, wherein the rear drives 1 1 in particular each comprise a rear motor 12, more preferably an electric motor, and a rear propeller 13. The rear propeller 13 are here folded against the direction of flight.

Likewise, a front drive 16 is arranged at the free end of each front nacelle 15, the front drives 16 in particular each comprising a front engine 17, more preferably an electric motor, and a front propeller 18.

To operate the drives 1 1, 16 further required parts, such as batteries, motor controller or motor plate, etc., are not shown here, however, the skilled person well known. These parts are preferably housed in the hull 2 or the gondolas 10, 15.

The motors 12, 17 and propellers 13, 18 of the two drives 1 1, 16 are each pivotally mounted by means of a pivot joint 14, 19 on the gondolas 10, 15. The rear drives 1 1 are in this case from a downward position (FIGS. 1, 2, 5), in which the axis of the motors 12 is lowered. right, opposite to the direction of flight H in a horizontal position pivotally (Fig. 3, 4, 6, 7), in which the axes of the motors 12 are aligned horizontally. The front drives 16 are pivotable in the direction of flight H into a horizontal position from an upwardly directed position (FIGS. 1, 2, 5), in which the axis of the motors 17 run vertically (FIGS. 3, 4, 6, 7). in which the axes of the motors 17 are aligned horizontally.

The two rear propellers 13 have a larger diameter than the front propellers 18 (see also Fig. 9). In addition, in the two rear propellers 13, the quotient of diameter divided by pitch is greater than in the case of the front drives, preferably greater by at least 25%, more preferably greater by at least 50%, for example by more than 100%. It is also possible and, in some cases, preferred that the quotient of diameter divided by pitch at the rear propellers 13 be 150%, for example 200%, larger than for the front drives 16.

As can be seen from Figures 2, 4 and 8, the center of gravity 20 of the aircraft 1 is off-center with respect to the rear and the front drives 1 1, 16 are arranged. Although the position of the center of gravity 20 is dependent on in particular the pivot states of the drives 1 1, 16. The off-center position of the center of mass 20 but applies to each of these pivot states. Corresponding to the plan view of Fig. 8, the center of mass 20 is closer to the rear drives 1 1 as to the front drives 16. As further illustrated in the detail plan view of Fig. 9, showing the two gondolas 10, 15 and the drives attached thereto 1 1, 16, the distance d1 of the rear drive 1 1 to the gravity axis 21, which passes through the center of mass 20 and perpendicular to the longitudinal axis 22 of the aircraft 1, is smaller than the distance d2 of the front drive 16 to the gravity axis 21st The lever arm of the rear drives 1 1 may preferably be at least 10%, for example by more than 20% or more 30%, shorter than the lever arm of the front drives 16, wherein the Lever arms are related to the shortest distance to the gravity axis 21. In a specifically implemented embodiment, the distance d2 of the lever arms of the motor axis 12a of the front drives 1 1 to the heavy axis 21 was 400 mm, while the length of the lever arms (distance d2) from the motor axis 17a of the rear drives 16 to the heavy axis 21 was 240 mm , The latter lever arm was thus 40% shorter than the aforementioned lever arm.

1 and 2, the aircraft 1 is shown in the floating position in which it starts in the starting direction S and lands in the direction L of the country. In this case, the two rear propellers 13 are pivoted downward and push the aircraft 1 in the direction S, while the two front propeller 18 are pivoted upward and also pull the aircraft 1 in the direction S.

It is not mandatory that the aircraft 1 in the hover position is aligned exactly horizontally. For example, it is readily possible for the tail 3 to hang at a small angle, for example about 10 °, relative to the nose 4.

3 and 4, the aircraft 1 is shown in travel or horizontal flight in which it flies in the horizontal direction of flight H. Here, the two rear propeller 13 are pivoted backwards against the direction of flight H and folded, while the two front propeller 18 are pivoted forward in the direction of flight H. Only these two front propeller 18 are responsible for propulsion in horizontal flight in the illustrated embodiment.

In FIGS. 5-7, the transitions between the different states are again shown in fragmentary side view, in particular without the fuselage 2. In Fig. 5, the rear motors 12 and the front motors 17 are in the position in which the aircraft 1 starts. In this floating state, the drives 1 1 down and the drives 16 are still pivoted up. For horizontal flight, the drives 1 1 according to FIG. 6 pivot backwards against the direction of flight H (arrow f1) and the front drives 16 forward in the direction of flight H (arrow f2). When flying away then fold the two leaves of the two rear propeller 13 due to the wind backwards against the direction of flight H (arrows f3), so that the rear propeller 13 does not contribute to propulsion. According to FIG. 7, the front drives 16 are pivoted upward again (arrow f5) during the transition from horizontal flight to the suspended state, while the rear drives 1 1 are started again and swiveled downwards (arrow f4). As a result of this starting, the propellers 13 unfold again due to the centrifugal force.

According to take over the rear drives 1 1 more than 50% of the hovering thrust necessary for hovering and less than 50% of the propulsive force in horizontal flight. In contrast, take over the front drives 16 less than 50% of hovering force necessary to levitate the aircraft 1 and more than 50% of the propulsion force in horizontal flight apply. In the present embodiment, the rear drives 16 are even not involved in the propulsion at all, since they fold on or off due to the wind.

The above-mentioned task distribution of the rear and front drives 1 1, 16 is realized in the embodiment shown in the figures, in particular by the displacement of the center of mass 20. Furthermore, the higher quotient of diameter divided by the slope of the rear drives contributes to an increase in efficiency of the hovering flight. The smaller quotient of diameter divided by the slope of the front drives contributes to an increase in efficiency of horizontal flight.

The control of the drives 1 1, 16, the propeller 13, 18, the ailerons 8 a, 8 b, etc. can be done manually, semi-automatically or automatically. In particular, especially the transition between the two flight conditions (hovering with front and rear drives switched on - horizontal flies only with front drives connected) can be realized either manually or automatically. Then, in particular, the propeller speeds are adjusted.

The invention has been described in more detail with reference to an embodiment, but is not limited to this. Variations within the scope of the claims are also possible as a combination of features, even if they are shown and described in different embodiments.

In particular, the aircraft according to the invention can also be controlled by humans and / or used to carry one or more people. In particular, the aircraft according to the invention is suitable as a drone for transporting goods, for controlling and securing the airspace or areas on the ground, for research purposes, for imaging, etc.

LIST OF REFERENCES

1 aircraft

2 aircraft fuselage

3 rear

4 nose

5 wings

6 tail unit

7 V tail

7a elevator

8a first aileron

8b second aileron

9a Stand kufe

9b Stand kufe

10 gondolas for rear drives

1 1 rear drives

12 rear engines

12a engine axle

13 rear propellers

14 swivel joint

15 gondolas for front drives

16 front drives

17 front engines

17a motor axle

18 front propellers

19 swivel joint

20 center of gravity of the aircraft

21 gravity axis

22 longitudinal axis of the aircraft

S start direction

L landing direction

H horizontal flight direction

d1 distance of the motor axis 2a to the heavy axis 21 d2 distance of the motor axis 17a to the heavy axis 21 f1 -f5 pivoting directions

Claims

Patent claims

1. Aircraft (1), preferably unmanned aerial vehicle (UAV), drone and / or unmanned aerial vehicle (UAS), comprising:

a rigid wing (5), which is oriented substantially horizontally both in hover and in horizontal flight and allows aerodynamic horizontal flight, and

with respect to the center of gravity (20) of the aircraft (1) at least one in horizontal flight direction rear controllable drive (1 1), comprising a rear motor (12) and a rear motor (12) driven rear propeller (13), and at least a front controllable drive (16) seen in horizontal flight direction, comprising a front engine (17) and a propeller (18) driven by the front engine (17), the engines (12, 17) preferably being electric motors, and wherein at least a part of the Drives (1 1, 16) are pivotable by means of a respective pivoting mechanism between a vertical start position for the hover and a horizontal flight position for the horizontal or cruise flight,

characterized in that the at least one rear or front drive (1 1, 16) is arranged and designed such that it applies more than 50% of the hovering thrust force necessary for hovering the aircraft (1) and less than 50% of the propelling force in horizontal flight, while the at least one front or rear drive (16, 11) is arranged and designed such that it applies less than 50% of the hovering thrust force necessary to levitate the aircraft (1) and more than 50% of the propulsive force in horizontal flight.

2. Aircraft (1) according to claim 1, characterized in that two rear and two front drives (1 1, 16) are provided.

3. Aircraft (1) according to claim 1, characterized in that two rear drives (1 1) and a front drive (16), or a rear drive (1 1) and two front drives (16) are provided.

4. Aircraft (1) according to at least one of the preceding claims, characterized in that the center of gravity (20) of the aircraft (1) off-center with respect to the rear and the front propeller (13, 18) is arranged.

5. Aircraft (1) according to at least one of the preceding claims, characterized in that the center of mass (20) of the aircraft (1) is arranged closer to those drives which apply more than 50% of the hover thrust.

6. Aircraft (1) according to at least one of the preceding claims, characterized in that the one or more said rear or front drives (1 1, 16) for providing more than 55%, preferably more than 60%, of the hover thrust are designed , while the one or more front or rear drives (16, 1 1) are designed to provide less than 45%, preferably less than 40%, of hovering thrust.

7. Aircraft (1) according to at least one of the preceding claims, characterized in that the one or more said rear or front drives (1 1, 16) for providing more than 65%, preferably more than 70%, of the hover thrust are designed while the one or more front or rear drives (16, 11) less than 35%, preferably less than 30%, of hovering thrust are designed.

8. Aircraft (1) according to at least one of the preceding claims, characterized in that the one or more said rear or front drives (1 1, 16) are designed to provide more than 80%, for example, more than 90% of the hover thrust force , while the one or more front or rear drives (16, 1 1) for providing less than 20%, for example, less than 10%, the hover thrust force are designed.

9. Aircraft (1) according to at least one of the preceding claims, characterized in that the front and the rear drives (16, 1 1) both for providing the hovering of the aircraft (1) necessary hover thrust force as well as to provide propulsion force in Horizontalf contribute.

10. Aircraft (1) according to at least one of claims 1 to 8, characterized in that the front and the rear drives (16, 1 1) all contribute to the provision of levitation of the aircraft (1) necessary hover thrust, while only a part this drives (1 1, 16) contributes to the provision of propulsive force in horizontal flight and the other part of the drives is switched off.

1 1. Aircraft (1) according to at least one of the preceding claims, characterized in that the diameter of the propeller (13) of those drives (1 1), which apply more than 50% of the hover thrust, is greater than the diameter of the propeller (18 ), which apply less than 50% of the hovering thrust, preferably at least 5% larger, more preferably at least 10% larger.

12. Aircraft (1) according to at least one of the preceding claims, characterized in that the quotient of diameter divided by the slope of the drives, which apply more than 50% of the hover thrust, is greater than in the drives, the less than 50% of Apply hovering thrust.

13. Aircraft (1) according to at least one of the preceding claims, characterized in that all drives (1 1, 16) are pivotable by means of a respective pivot mechanism between a vertical start position for the hover and a horizontal flight position for the horizontal flight.

14. Aircraft (1) according to at least one of claims 1 to 9, characterized in that only those drives (16) by means of a respective pivoting mechanism between a vertical start position for the hover and a horizontal flight position for horizontal flight are pivotable, which contribute to the propulsion in horizontal flight ,

15. Aircraft (1) according to at least one of the preceding claims, characterized in that all drives (1 1, 16) on the wing (5) are arranged.

16. Aircraft (1) according to at least one of the preceding claims, characterized in that the or the rear propeller (13) in hovering up or down and pivot for horizontal flight up or down and against the direction of flight, preferably by 75 ° to 105 °, more preferably by 85 ° to 95 °, while the front propeller (s) (18) are pointing upwards in hovering flight and are inclined downwards for horizontal flight and forward in the direction of flight. ken, preferably by 75 ° to 105 °, more preferably by 85 ° to 95 °.

17. Aircraft (1) according to at least one of the preceding claims, characterized in that the rear or the front propeller (13, 18) are designed hinged for horizontal flight.

18. Aircraft (1) according to at least one of the preceding claims, characterized in that the propellers (13) of those drives which apply more than 50% of the hovering thrust, are formed hinged.

19. Aircraft (1) according to at least one of the preceding claims, characterized in that the or the rear propeller (13) in horizontal flight against the flight direction (H) are formed hinged, preferably due to the action of wind forces.

20. Aircraft (1) according to at least one of the preceding claims, characterized in that a control device for controlling the motors (12, 17) is provided such that the aircraft (1) is automatically preserved in a stable hovering flight.