Vertical take-off aircraft

Abstract

The invention relates to a vertical take-off aircraft (1) which is designed as a tail-sitter and, after the take-off, transitions in full from the substantially vertical hover attitude into the horizontal attitude, comprising: an aircraft fuselage (2); a rigid wing (5), fixedly connected to the aircraft fuselage (2); and at least one motor-driven propeller (11), which is arranged so as to be fixed in position and has propeller blades (12); and a motor-driven rotor (16), which is arranged so as to be fixed in position and has rotor blades (17); wherein the propeller (11) is driven at least in horizontal flight by a first drive shaft (13) and the rotor (16) is driven in hovering flight, but not after the transition into the regular horizontal flight, by a second driveshaft (18); wherein the first and the second driveshafts (13, 18) extend coaxially with one another; and wherein the rotor blades (17) are designed so they can be folded in with respect to the aircraft fuselage (2) in horizontal flight of the aircraft (2), while the propeller blades (12) are not designed so they can be folded in with respect to the aircraft fuselage (2). The invention also relates to a method for operating a vertical take-off aircraft (1).

Description

[0001] Vertical takeoff aircraft

[0002] The invention relates to a vertical take-off aircraft which is designed as a tail-starter - also called a tailsitter - and which, after take-off, transitions as a whole from the essentially vertical hovering position to the horizontal flight position.

[0003] Vertical takeoff aircraft come in a wide variety of configurations. In one type, the aircraft remains in the same attitude both in hover and in horizontal flight. Tilt-rotors are often used in such aircraft, where the aircraft takes off and hovers vertically with the rotors tilted upward. After reaching a minimum altitude, the tilt-rotors are tilted forward so that the rotor axis is now essentially horizontal. The tilt-rotors then act as propellers and provide forward thrust.

[0004] Another type of aircraft is the so-called tail-starter or tail-sitter. A tail-starter takes off with the nose pointing upward (similar to a rocket) and, after reaching a minimum altitude, returns to a horizontal position as a whole. The present invention relates to such a tail-starter.

[0005] US Patent No. 5,289,994 describes a vertical takeoff aircraft in the form of a tail-launcher with two coaxial, counter-rotating propellers mounted on the nose, each of which has different diameters. Both propellers support both hover and horizontal flight.

[0006] EP 3 290 338 A1 also describes a vertical takeoff aircraft designed as a tail-launch aircraft with two propellers or rotors arranged at the nose, which rotate in opposite directions for takeoff. In horizontal flight, the rear rotor is placed in a fixed position, serving as a wing, while the front rotor acts as a propeller, providing propulsion. When the aircraft is on the ground, the propeller or rotor blades are folded against the fuselage. EP 3 290 337 A1 describes a similar design, but with the addition of a small rear propeller.

[0007] US 2018 / 0118334 A1 discloses an aircraft system in which several vertical take-off and landing engines are detachably arranged side by side along the leading edge of a wing element not coupled to a fuselage, for example by means of magnets. The individual vertical take-off and landing engines can thus detach from the wing element and enter an independent flight mode. Furthermore, the vertical take-off and landing engines are designed to take off from the ground in a vertical position as tail-start engines and subsequently transition to a horizontal flight attitude. These tail-start engines also have two rotors arranged on the nose, which are driven both during take-off and during horizontal flight.

[0008] The familiar vertical takeoff and landing aircraft suffer from the fact that enabling pinpoint takeoff and landing usually results in significant losses in cruise speed and range. Furthermore, the complexity of the aircraft increases due to the additional number of components required for vertical takeoff and landing.

[0009] The object of the present invention is to provide an aircraft designed as a rear-starter with a simple structure but high efficiency.

[0010] This object is achieved by an aircraft having the features of claim 1 and a method according to claim 18. The aircraft according to the invention is characterized in that it has at least one propeller and at least one rotor, both of which are arranged coaxially one behind the other. Furthermore, the rotor blades of the at least one rotor are folded toward the aircraft fuselage during normal or regular operation of horizontal or cruise flight, in particular outside of the takeoff and landing phases. Only the at least one propeller whose propeller blades are not designed to be foldable is responsible for regular horizontal flight in the forward direction.The term "regular horizontal flight" refers to efficient cruise flight operations; special flight situations, such as braking the aircraft in horizontal flight using the rotor to prepare for a vertical landing, are not included in the phrase "regular horizontal flight." The same applies, for example, to initiating the transition from hover to horizontal flight, during which the rotor preferably rotates several more times until it folds toward the fuselage.

[0011] Furthermore, a rigid wing is provided on the fuselage, which is firmly connected to the fuselage and is responsible for the dynamic lift of the aircraft.

[0012] In this description, the term "rotor" is used as in the case of helicopters, since they are active during hovering (takeoff and landing, including, if necessary, the transition phases from hovering to horizontal flight and back). "Propellers" in the sense of the invention are particularly involved in horizontal flight, but can also support hovering.

[0013] The advantages of the invention are particularly evident in the fact that the aircraft according to the invention requires very few additional components to enable vertical or hover flight. This results in a simple and lightweight design. Furthermore, folding the rotor blades towards the aircraft fuselage results in only a very slight increase in aerodynamic drag compared to a rotorless design. It is preferred that the rotor blades pivot or fold particularly accurately against the fuselage contour during horizontal flight. This eliminates the need for additional surface area to be washed over during horizontal flight. Despite this simple and lightweight design, the aircraft according to the invention can take off and land with pinpoint accuracy.

[0014] By configuring the aircraft with (at least) one stationary propeller (i.e. one that cannot move relative to the fuselage and in particular cannot be tilted), and with propeller blades that cannot be folded against the fuselage, and one stationary rotor (i.e. one that cannot move relative to the fuselage and in particular cannot be tilted), which, however, has rotor blades that can be folded towards the fuselage, very high efficiency can be achieved in both hovering and horizontal flight. This avoids mechanically complex parts such as pitch adjustment of the propeller or rotor, which are costly not only to produce but also to operate and maintain. The omission of pivoting wings also simplifies the design. By eliminating pivoting mechanisms, the weight of the aircraft is reduced, its robustness is increased, and its reliability is improved.

[0015] The aircraft according to the invention can be designed as an unmanned aerial vehicle (UAV), drone and / or unmanned aerial system (UAS) or also for the transport of persons.

[0016] It has proven particularly advantageous for aircraft to have just a single propeller and a single rotor. Their two coincident axes run longitudinally of the aircraft and preferably coincide with the aircraft's longitudinal axis (up to about 2° "engine dive": the air moves upwards in front of the aircraft due to the lift on the wing. To position the propeller precisely in the direction of flow, it is inclined downwards by about 2° in the direction of flight). The propeller and rotor are the only means of taking off the aircraft vertically, then hovering to a minimum altitude, then flying horizontally to its target and landing there. According to current calculations, additional propulsion is not necessary, particularly for aircraft including a total load of up to approximately 30 or 40 kg, or even up to 150 kg.

[0017] The single-propeller, single-rotor configuration with a coaxial arrangement eliminates the need for additional spaced-apart motors and propellers. This mounting of the rotor and propeller in or on the fuselage significantly reduces drag during flight, as can be mathematically proven by considering the "cube-square law" in conjunction with Bernoulli's law of drag. The compact arrangement also reduces the cable lengths in the fuselage compared to a design with multiple propellers and rotors, resulting in material and weight savings.

[0018] When reference is made to "the propeller" and "the rotor" below, this also includes designs with more than one propeller and more than one rotor—even if the design with a single propeller and a single rotor is currently considered the preferred variant. In other words, reference is made to "the at least one propeller" and "the at least one rotor" instead of always referring to "the propeller" and "the rotor" for simplicity.

[0019] Advantageously, the first drive shaft or the second drive shaft is designed as a hollow shaft, while the second drive shaft or the first drive shaft runs within the said first or second drive shaft. This results in a compact and relatively simple design. This allows the propeller and rotor to be arranged close together, for example, in the nose area. With such an arrangement, the propellers are protected from, for example, grass on the ground.

[0020] According to a preferred embodiment, the propeller is part of a first drive, which further comprises a first electric motor. The first electric motor is expediently connected to an electrical storage device (in particular one or more accumulators). The rotor, on the other hand, is part of a second drive, which further comprises a second electric motor. The second electric motor is expediently connected to an electrical storage device (in particular one or more accumulators). The electrical storage device for the first electric motor can be the same as that for the second electric motor. However, different electrical storage devices can also be provided. Partial joint use of the same storage device(s) by both electric motors is also possible. The first drive is provided and configured to drive the associated propeller at least in horizontal flight.In contrast, the second drive is designed and configured to drive the rotor particularly preferably only in hovering flight, but not in normal or regular horizontal flight.

[0021] By providing a first and a second drive, the energy consumption of the aircraft according to the invention can be optimized. The second drive is designed in particular for hovering, i.e. taking off and landing, whereas the first drive can (but does not have to) support hovering, but is otherwise solely responsible for propulsion in regular horizontal flight. In horizontal flight, lift is generated by the shape of the aircraft, whereas in hovering it is primarily generated by the rotor. Each of the drives can therefore be specifically configured and designed for its own tasks. By operating at least one first engine alone in regular horizontal or cruise flight, very quiet horizontal or cruise flight can also be achieved. Even when the two propellers are arranged at the nose of the aircraft (i.e. designed as a tractor propeller), noise levels are very low.

[0022] According to an alternative, only one drive with an electric motor is provided for driving both the propeller and the rotor, wherein the electric motor is connected to an electrical storage device (in particular, one or more accumulators). Here, the first drive shaft and the second drive shaft are identical at least in sections and can be coupled to one another by means of a gearbox and a clutch for connecting or disconnecting the drive transmission in such a way that the propeller is driven by the said electric motor, at least for horizontal flight, and the rotor is driven by the said electric motor during hovering, but not during regular horizontal flight.

[0023] It is particularly preferable for the aircraft and its engines to be designed so that the propeller achieves its best efficiency when the aircraft is in cruise flight. If, for example, large differences in altitude must be overcome during flight missions, resulting in a steady climb, the propeller and / or engine may need to be adjusted accordingly.

[0024] The rotor is preferably designed to keep the aircraft in a hover in an energy-efficient, controllable, and quiet manner. To keep the additional weight caused by the propulsion as low as possible, the rotor is preferably optimized for a very small speed window around the hover position. Its maximum speed, at which it still provides thrust, is significantly below the aircraft's minimum flight speed. Furthermore, the rotor's task includes the aircraft's climb and descent during takeoff and the transition from hover to level flight. The rotor can also be used to decelerate the high flight speed during the transition from level flight to hover, allowing for a particularly fast and precise approach to the landing point.This happens when the rotor is still driven by the corresponding engine while the aircraft is still at high speed in horizontal flight; horizontal flight during the braking process caused by the rotor operation is a special mode of horizontal flight and therefore cannot be subsumed under the term "regular or normal horizontal flight". Although the oncoming air pushes the propeller towards the fuselage, the centrifugal force caused by the rotation predominates and the rotor unfolds. The now unfolded rotor is then driven like a wind turbine, i.e. it autorotates and slows down the air flowing through its rotor plane. In this way, the aircraft's kinetic energy can even be recovered and reused to a certain extent. This braking effect can also be used to carry out particularly steep descent maneuvers, whereby here too some of the kinetic as well as the potential energy can be recovered.It is also technically possible, although challenging due to the fixed pitch (angle of attack) of the rotor, to realize an autorotating landing as is known from helicopters.

[0025] The aircraft is preferably designed to be particularly insensitive to weather and environmental influences, thus making operation safe and predictable. This is preferably achieved, among other things, by the fact that it is only flightworthy shortly below cruising speed. This ensures that the aircraft completes its cruising flight at its most efficient operating point. Together with a selected minimum flight speed of preferably over 100 km / h, gusts of wind have a reduced influence on the aircraft's flight movements and thus also on the additional structural loads caused by them. This also allows a particularly small wing size to be realized, which in turn results in compact transport dimensions, low weight, and low susceptibility to icing. This avoids the fragile wing structures known from model aircraft, which are easily damaged in everyday use.

[0026] The aircraft must be designed so that its rotor can rotate freely and without collision, even when only partially extended or retracted. This is important, for example, so that it can perform its braking function described above. However, even when the rotor is shut down—that is, after initiating the transition from hover to level flight—the rotor continues to rotate a few revolutions while folding toward the fuselage and coming to a complete stop.

[0027] The folding of the rotor blades is particularly preferably achieved at least partially due to the airstream pushing against the rotor blades after the aircraft has transitioned from a hover to a horizontal flight attitude. The force exerted by the airstream against the blades of the then-deactivated rotor engine pushes the rotor blades into a passive position on or near the aircraft fuselage and remains there until the rotor is powered again, particularly after or during the transition from horizontal flight to a hover in preparation for landing.

[0028] Alternatively or additionally, the blades of the rotor motor, which is switched off after the intended altitude has been reached, are designed so that they can be actively folded by means of their own drive. According to a further alternative, when the rotor motor is no longer driven, the rotor blades fold towards the aircraft fuselage due to, for example, a spring and / or magnetic force. When the rotor motor is switched on again, this spring and / or magnetic force is overcome by the centrifugal force of the rotor blades and the rotor blades fold open again. In one variant of the invention, the propeller is also used for hovering, preferably including takeoff. In this case, in addition to the second electric motor, the first electric motor is also designed and configured to drive the propeller during takeoff and / or hovering.

[0029] The at least one propeller and the at least one rotor, which according to the invention are arranged coaxially to one another, are particularly preferably arranged one behind the other at the nose of the aircraft, i.e. at the front end of the aircraft fuselage. The distance between the propeller and rotor is preferably between 1 and 20 cm, preferably between 1 and 15 cm and particularly preferably between 1 and 10 cm. The above-mentioned distances are suitable, for example, for an aircraft weighing 10 kg; for heavier aircraft, the distance can advantageously be greater. The distance between the propellers mainly determines that no collision occurs. The foldability of the rotor blades requires that the propeller is arranged in front of the rotor, viewed in the direction of flight.

[0030] Due to the aircraft's rear-starter design, the rotor is positioned well above the ground during takeoff and landing, which protects it from collisions with objects on the ground.

[0031] According to one alternative, the propeller is arranged at the rear of the aircraft fuselage and the rotor at the nose of the aircraft fuselage. Here, too, the rotor is far from the ground and therefore protected from collisions with obstacles. The propeller arranged at the rear, on the other hand, is preferably only used in horizontal flight (and possibly during the transition to and / or from horizontal flight). Particularly preferably, the rotor sweeps a larger total area during operation than the propeller. In relation to the external dimensions of the aircraft, it is advantageous to choose the largest possible rotor diameter in order to generate the required lift with the smallest possible circular area loading and thus enable efficient hovering. The circular area covered by the propeller, on the other hand, can be considerably smaller in order to achieve the necessary forward thrust of the aircraft.The area swept by the rotor is preferably greater than 300%, preferably greater than 500%, for example greater than 800%, of the area swept by the propeller. Furthermore, it is preferred if the area swept by the rotor during operation is less than 1500%, for example less than 1000%, of the area swept by the propeller. Various parameters and their desired prioritization are taken into account for the appropriate selection of the area ratio, for example, weight, noise emissions, maneuverability, etc.

[0032] Preferably, elevons are provided on the wing, combining the functions of both ailerons and elevators. This design reduces the number of required components without compromising overall control accuracy.

[0033] In a particularly preferred embodiment of the aircraft according to the invention, the rigid wing, which is firmly or permanently connected to the aircraft fuselage, has a forward sweep. Such a design advantageously achieves two things. On the one hand, the large rotor can fold and unfold towards the fuselage without collision, without the aircraft's center of gravity being shifted too far to the rear. On the other hand, the rotor can apply an airflow to the wing at its control surfaces (generally understood to mean: elevator, ailerons, rudder, elevons, ...), for example the above-mentioned elevons. Taking into account the known strong constriction of the rotor jet behind the rotor circular surface during hovering, the rear, ieThe control surfaces located aft on the wing should preferably be placed precisely in the section where the greatest airflow velocity occurs, resulting from the air flowing against the aircraft's nose during hovering and ascending, and in particular from the aforementioned airflow velocity generated by the rotor. This achieves good control authority during hovering. The same control surfaces on the wing are also preferably positioned at an optimized position to take over elevator control on a swept-back wing—with the aforementioned design of these control surfaces as elevons—and to adjust the airspeed trim with minimal drag.

[0034] The aforementioned forward sweep is preferably designed in at least two stages, with the sweep section closest to the fuselage (as seen in the direction of flight) forming a larger angle with the aircraft fuselage than the sweep section further away from the fuselage. This provides ample space for the rotor during folding and unfolding.

[0035] Particularly preferably, in addition to the rigid wing, a vertical stabilizer is provided at the rear of the aircraft, which accommodates at least parts of the landing gear used to land the aircraft. Alternatively, or in addition to the vertical stabilizer, a horizontal stabilizer is provided at the rear of the aircraft.

[0036] Advantageously, supports are provided on the wing and the vertical stabilizer and / or the horizontal stabilizer to support the aircraft on the ground. Two supports are preferably arranged on the wing and two on the vertical stabilizer or horizontal stabilizer. Alternatively, supports are arranged on the vertical stabilizer and horizontal stabilizer, but preferably not on the wing. The vertical stabilizer, if present, preferably protrudes beyond the fuselage on two sides. According to an alternative, the vertical stabilizer protrudes from the fuselage on only one side.

[0037] An autopilot is particularly preferred for controlling the transition between the flight states of hovering and horizontal flight. This can either be assisted by manual commands, for example, via switches, or, more preferably, can take over control of the aircraft fully automatically. An additional option for radio control can also be advantageous. Preferably, the drive speeds of the electric motors and control surfaces are always adjusted with the assistance of a computer. In automated operation, for example, only the flight route needs to be planned in advance.

[0038] The aircraft according to the invention can be designed not only for the transport of objects, but also of one or more people.

[0039] The invention also relates to a method for operating a vertical take-off aircraft according to claim 18.

[0040] The takeoff procedure for the aircraft according to the invention is preferably as follows: The unfolded rotor (and optionally also the propeller) is driven to take off the aircraft and bring it into hover at a minimum altitude. By controlling the control surfaces (elevons, rudder) and with the aid of the propeller, the aircraft, with the rotor still driven, after passing a highest point, goes into a downward flight with the nose pointing diagonally (to vertically) downwards so that the aircraft reaches a high speed due to gravity, at which it can fly in a stable descent. At this point, the motor, preferably an electric motor, of the rotor is now switched off and the rotor blades fold towards the fuselage due to the airstream. Finally, with the control surfaces controlled accordingly and the propeller driven, the aircraft transitions from the downward flight to horizontal or cruising flight.The propeller is designed to optimally generate the thrust required for cruising or level flight. The rotor, in turn, is designed to operate optimally during hovering and slow, power-saving climbs. Since the rotor does not have to operate at high flight speeds, modifications are particularly easy to implement so that it sits optimally against the fuselage. The dive maneuver allows the necessary flight speed to be built up without one of the engines having to take over this task, which would otherwise lead to a suboptimal compromise that diminishes the respective main tasks (i.e., hovering with the help of one engine, cruising with the help of the other).

[0041] Landing is preferably carried out in a conventional manner for tail-takeoff aircraft, meaning the aircraft transitions from horizontal flight to a hover, where the rotor is deployed and powered. In hover, the aircraft then lands with its tail on the ground. Due to the rotor design, which is optimal for hovering, a braking maneuver occurs when the rotor deploys, during which the minimum horizontal speed can be undercut before the rotor can provide thrust. Therefore, similar to takeoff, the speed between hover and minimum horizontal speed should be achieved within a finite, defined time.

[0042] Calculations have shown that, with the inventive design enabling vertical takeoff and landing, electric-powered models weighing between 2 and 25 kg only lose about 15% of their horizontal flight performance, while most known configurations lose 50% to 70% or more. The invention is explained in more detail below with the aid of the figures. They show:

[0043] Fig. 1a, 1b an oblique view of a first embodiment of an aircraft according to the invention on the ground with folded rotor blades (Fig. 1a) and unfolded rotor blades (Fig. 1b);

[0044] Fig. 2a, 2b an oblique view (Fig. 2a) from the rear and an oblique view from the front (Fig. 2b) of the aircraft of Fig. 1 in horizontal flight;

[0045] Fig. 3e-3f a transition of the aircraft according to the invention from takeoff (Fig. 3a) to horizontal flight (Fig. 3f),

[0046] Fig. 4 is an oblique view of a second embodiment of an aircraft according to the invention on the ground with the rotor blades folded in or retracted.

[0047] Figures 1a and 1b show a first embodiment of a vertical takeoff aircraft 1 according to the invention—constructed in a kite configuration—in the form of a tail launcher in takeoff position on the ground. Figures 2a-b show the aircraft 1 in an oblique rear view and a front view in horizontal flight, respectively. The aircraft 1 is configured as an unmanned drone.

[0048] The aircraft 1 has a single-piece, relatively compact fuselage 2 with a nose 3 and a tail 4. A wing 5, permanently and firmly connected to the fuselage 2, in the rear half of the fuselage 2 enables aerodynamic horizontal flight. The wing 5 has a forward sweep, with a swept section 5a near the fuselage (seen in the direction of flight) forming a larger angle α with the longitudinal axis of the fuselage 2 than an angle β formed by a swept section 5b far from the fuselage with the longitudinal axis of the fuselage 2.

[0049] On the wing 5 - in the embodiment shown on the swept section 5a close to the fuselage - 2 elevons 6 are provided on both sides of the aircraft fuselage, which, as is known, combine both elevators and ailerons.

[0050] From the tail 4, a vertical stabilizer 7 also protrudes perpendicularly to the wing 5 on both sides of the aircraft fuselage 2. The vertical stabilizer 7 also serves partially as the landing gear, with which the aircraft 1 supports itself on the ground. For this purpose, two supports 21 are provided at the two outermost ends of the vertical stabilizer 7. In this case, two supports 20 are also arranged on the wing 5, located in the area of ​​the transition from the swept section 5a near the fuselage to the swept section 5b far from the fuselage.

[0051] The vertical stabilizer 7 also features rudder 7a, which serve the aircraft's lateral control in the usual way. The rudder 7a is preferably deflected in opposite directions during hovering to compensate for the rotor torque. Rudder deflections of up to 80° are useful during hovering to maximize maneuverability. During cruise flight, less than 5° is usually sufficient.

[0052] At the front of the nose 3, a propeller 11 with rigid propeller blades 12 that are not foldable relative to the aircraft fuselage is provided, which is part of a drive 10. The drive 10 also comprises a first drive shaft 13 and an electric motor 14 connected to this drive shaft 13 (indicated in Fig. 1 a within the aircraft fuselage 2), which is supplied with electrical energy by an electrical storage device (not shown).

[0053] A rotor 16 is provided a short distance behind the propeller 11. The rotor 16 is part of a drive 15, which also includes a second drive shaft 18 and a second electric motor 19 (indicated in Fig. 1a within the aircraft fuselage 2). The second drive shaft 18 connects the rotor 16 to the electric motor 19. The electric motor 19 is supplied with electrical energy by an electrical storage device (not shown). The two electric motors 14, 19 can be powered by a common electrical storage device or by different electrical storage devices.

[0054] According to the invention, the first drive shaft 13 and the second drive shaft 18 extend coaxially to one another. In the exemplary embodiment illustrated in the figures, the second drive shaft 18 is designed as a hollow shaft in which the first drive shaft 13 runs.

[0055] Furthermore, according to the invention, the rotor blades 17 of the rotor 16 are designed to be foldable toward the aircraft fuselage 2 (Fig. 1 a). For takeoff and landing, as well as for hovering, the rotor blades 17 are unfolded (Fig. 1 b), while during normal horizontal cruising flight they are folded against the aircraft fuselage 2.

[0056] The folding of the rotor blades 17 can be achieved in various ways. In one variant, the airstream is sufficient to pivot the rotor blades 17 into the folded position when the second electric motor 19 is switched off and the rotor 16 is thus stationary. When the second electric motor 19 is switched on, particularly for landing the aircraft 1, the rotor blades 17 unfold again due to the centrifugal forces acting on them (condition as shown in Fig. 1 b).

[0057] In an alternative embodiment, the rotor blades 17 are designed to be actively foldable toward the aircraft fuselage 2 by their own drive and / or due to spring or magnetic force when the second electric motor 19 is switched off (not shown). The area swept by the rotor 16 is larger than the area swept by the propeller 11. Advantageously, the area swept by the rotor 16 is 5 to 15 times larger than the area swept by the propeller 11, although in certain embodiments, this range can also be exceeded or undershot.

[0058] The takeoff procedure of the aircraft 1 according to the invention shown in Figs. 1-3 until reaching the horizontal flight attitude is explained below with reference to Figs. 3a-3f. This maneuver is preferably carried out by means of an appropriately programmed autopilot installed in the aircraft 1. Beginning with the start of the second electric motor 19, the rotor blades 17 are unfolded by centrifugal force (cf. Figs. 1a and 1b) and the aircraft 1 lifts off from the ground in the takeoff direction S. The propeller 11 can assist this takeoff and the subsequent hovering by operating the first electric motor 14. According to Fig. 3b, the aircraft 1 flies vertically upwards and, shortly before reaching the targeted highest flight point HFP, transitions into a parabolic flight (Fig. 3c). When passing the highest flight point HFP (Fig. 3d) or shortly before or after, the second electric motor 19 is switched off, the rotor 16 stops and the first electric motor 14 is switched on.In the subsequent dive (Fig. 3e), the rotor blades 17 fold aerodynamically favorably against the aircraft fuselage 2. Upon reaching a minimum speed, for example 130 km / h, the aircraft 1 is sufficiently stable to be kept in the air in the horizontal flight attitude H (Fig. 3f).

[0059] Fig. 4 shows a perspective view of a second embodiment of an aircraft 1 according to the invention, which is also designed in a kite configuration. The structure of this aircraft 1 differs from the aircraft 1 according to Figs. 1-3 essentially in the design of the tail 4. The tail 4 of the aircraft 1 according to Fig. 4 has, in addition to the vertical stabilizer 7 with rudders 7a, a horizontal stabilizer 8 with elevators 8a. The vertical stabilizer 7 and the horizontal stabilizer 8 together form the landing gear.

[0060] At the two outermost ends of the vertical stabilizer 7, as in the embodiment shown in Figs. 1-3, supports 21 are provided. Corresponding supports 22 are also arranged at the outermost ends of the horizontal stabilizer 8. On the ground, the aircraft 1, as shown in Fig. 4, rests on the supports 21, 22. However, supports on the wing 5, as provided in the embodiment shown in Figs. 1-3, are not present.

[0061] In the embodiment shown in Fig. 4, the wings 5 ​​do not have any control surfaces, in particular no ailerons or elevons. Instead, the rudder 7a and the elevator 8a perform all control functions. However, it would be readily possible to provide additional control surfaces, for example, also on the wing 5; however, if a simplification of the overall design is desired, such additional control surfaces are preferably omitted.

[0062] The operation of the aircraft 1 of Fig. 4, including take-off, transition to horizontal flight and landing, corresponds to that of the aircraft 1 of Figs. 1-3, the control of the aircraft 1 of Fig. 4 now being taken over by means of the control surfaces, ie the rudder 7a and the elevator 8a.

[0063] The invention has been described in more detail with reference to two exemplary embodiments, which show designs as a drone (without passenger transport). Variants not shown in detail are possible within the claims. For example, designs other than the kite configuration are possible. In one of these variants, not shown, the propeller 11 is arranged on the tail 4, while the rotor 16 is still provided on the nose 3 of the aircraft 1. In an alternative, also not shown, a common drive is provided for the propeller 11 and the rotor 16, wherein the drive comprises only one electric motor with one or more electrical storage devices for driving both the propeller 11 and the rotor 16. In this case, the first and second drive shafts 13, 18 are identical at least in sections and can be coupled to one another by means of a gearbox and a clutch for connecting or disconnecting the drive power.

[0064] List of reference symbols

[0065] 1 aircraft

[0066] 2 aircraft fuselage

[0067] 3 Nose

[0068] 4 Rear

[0069] 5 wings

[0070] 5a near-torso arrow section

[0071] 5b arrow section away from the fuselage

[0072] 6 Elevon

[0073] 7 Vertical stabilizer

[0074] 7a Rudder

[0075] 8 horizontal stabilizer

[0076] 8a Elevator

[0077] 10 first drive

[0078] 11 propellers

[0079] 12 propeller blades

[0080] 13 first drive shaft

[0081] 14 first electric motor

[0082] 15 second drive

[0083] 16 Rotor

[0084] 17 rotor blades

[0085] 18 second drive shaft

[0086] 19 second electric motor

[0087] 20 Support on the wing

[0088] 21 Support on the vertical stabilizer

[0089] 22 Support on the horizontal stabilizer

[0090] S Start direction

[0091] H Horizontal flight direction

[0092] HFP highest flight point

Claims

Patent claims Vertical take-off aircraft (1) which is designed as a tail-starter and after take-off transitions from the substantially vertical hovering position as a whole into the horizontal flight position, comprising an aircraft fuselage (2), a rigid wing (5) firmly connected to the aircraft fuselage (2), and at least one stationary, motor-driven propeller (11) with propeller blades (12) and a stationary, motor-driven rotor (16) with rotor blades (17), wherein the propeller (11) is driven at least in horizontal flight via a first drive shaft (13) and the rotor (16) is driven in hovering flight, but not after transition to regular horizontal flight, via a second drive shaft (18), wherein the first and the second drive shaft (13, 18) extend coaxially to one another, and wherein the rotor blades (17) are designed to be foldable relative to the aircraft fuselage (2) in horizontal flight of the aircraft (1). are,while the propeller blades (12) are not designed to be foldable relative to the aircraft fuselage (2). Aircraft (1) according to claim 1, characterized in that a single propeller (11) and a single rotor (16) are provided. Aircraft (1) according to claim 1 or 2, characterized in that the rotor (16) sweeps a larger total area during operation than the propeller (11), preferably a total area at least five times larger. Aircraft (1) according to at least one of the preceding claims, characterized in that the first drive shaft (13) or the second drive shaft (18) is designed as a hollow shaft in which the second drive shaft (18) or the first drive shaft (13) extends. Aircraft (1) according to at least one of the preceding claims, characterized in that the propeller (11) is a component of a first drive (10) which further comprises a first electric motor (14), and in that the rotor (16) is a component of a second drive (15) which further comprises a second electric motor (19), wherein the first electric motor (14) is provided and configured to drive the associated propeller (11) at least in horizontal flight, and in that the second electric motor (19) is designed and configured to drive the rotor (16) in hovering flight, but not in regular horizontal flight.Aircraft (1) according to at least one of claims 1 to 5, characterized in that only one drive with an electric motor and an electrical storage device is provided for driving the propeller (11) and the rotor (16), wherein the first drive shaft (13) and the second drive shaft (18) are at least partially identical and can be coupled to one another by means of a gearbox and a clutch for connecting or disconnecting the drive power in order to drive the propeller (11) at least in horizontal flight and the rotor (16) in hovering flight, but not in regular horizontal flight, by the said electric motor. Aircraft (1) according to the preceding claim, characterized in that the rotor blades (17) can be passively folded towards the aircraft fuselage due to the airstream (F) when the rotor (16) is no longer driven in horizontal flight. Aircraft (1) according to the preceding claim, characterized in that the rotor blades (17) can be passively folded towards the aircraft fuselage due to the airstream (F) when the rotor (16) is no longer driven. Rotor (16) are designed to be actively foldable towards the aircraft fuselage (2) by means of their own drive and / or due to spring force and / or due to magnetic force. Aircraft (1) according to at least one of the preceding claims, characterized in that the propeller (11) can also be driven in hovering flight. Aircraft (1) according to at least one of the preceding claims, characterized in that the propeller (11) and the rotor (16) are arranged one behind the other on the nose (3) of the aircraft (1). Aircraft (1) according to at least one of the preceding claims up to the immediately preceding claim, characterized in that the propeller (11) is arranged on the tail (4) and the rotor (16) is arranged on the nose (3) of the aircraft (1). Aircraft (1) according to at least one of the preceding claims, characterized in that elevons (6) are provided on the wing (5), which combine the function of ailerons and elevator.Aircraft (1) according to at least one of the preceding claims, characterized in that the rigid wing (5) has a forward sweep. Aircraft (1) according to the preceding claim, characterized in that the forward sweep is formed in at least two stages, wherein the swept section (5a) closest to the fuselage forms a larger angle (□) with the aircraft fuselage (2) than the swept section (5b) further away from the fuselage. Aircraft (1) according to at least one of the preceding claims, characterized in that, in addition to the rigid wing (5), it has a vertical stabilizer (7) and / or a horizontal stabilizer (8) at the rear (4) of the aircraft (1), which accommodates at least parts of the landing gear. Aircraft (1) according to the preceding claim, characterized in that the vertical stabilizer (7) and / or the horizontal stabilizer (8) protrude beyond the aircraft fuselage (2) on two sides. Aircraft (1) according to at least one of the preceding claims, characterized in that supports (20, 21) are provided on the wing (5) and on the vertical stabilizer (7) and / or on the horizontal stabilizer (8), with which supports the aircraft (1) is supported on the ground.Method for operating a vertical take-off aircraft (1), in particular an aircraft (1) according to one of the preceding claims, which comprises an aircraft fuselage (2), a rigid wing (5) firmly connected to the aircraft fuselage (2), and at least one stationary, motor-driven propeller (11) with propeller blades (12) and a stationary, motor-driven rotor (16) with rotor blades (17), wherein the propeller (11) is driven via a first drive shaft (13) and the rotor (16) via a second drive shaft (18), wherein the first and the second drive shafts (13, 18) run coaxially to one another, wherein the aircraft (1) after take-off transitions as a whole from the essentially vertical hovering position to the horizontal flight position, wherein the rotor (16) is only operated in hovering flight, preferably but not in regular horizontal flight, and the propeller (11) is operated in horizontal flight and optionallyalso operated in hover flight. Method according to the preceding claim, characterized in that the aircraft (1) first exceeds a highest flight point (HFP) during the transition from hovering to horizontal flight.

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