Unmanned aircraft and operation method for the same

Abstract

An unmanned aircraft includes a propulsion system having a diesel or kerosene internal combustion engine and a charger device for engine charging. The propulsion system can be a hybrid propulsion system or a parallel hybrid propulsion system.

Claims

1. An unmanned aircraft, comprising: a propulsion system that comprises a diesel or kerosene internal combustion engine, wherein the propulsion system is a hybrid propulsion system which, in addition to the internal combustion engine, comprises an electric motor and an energy storage device configured to store electric energy for driving the electric motor; a charging device configured to charge the internal combustion engine of the unmanned aircraft; and a controller configured to control the charging device or the hybrid propulsion in accordance with flight operation parameters, wherein the charging device is designed for multi-stage charging, wherein the charging device comprises multiple exhaust gas turbines that are connected in series, wherein the charging device additionally comprises at least one mechanical charger configured to be driveable by the electric motor of the hybrid propulsion, and wherein the controller is configured to control charging of the charging device with or without the use of exhaust gas energy and by the use of mechanical energy from the internal combustion engine or from the electric motor.

2. The unmanned aircraft of claim 1, wherein the hybrid propulsion system comprises a switchable coupling device with which the internal combustion engine or the electric motor is selectively connected to a thrust generator.

3. The unmanned aircraft of claim 1, wherein the internal combustion engine and the electric motor are configured to be selectively operated in parallel or in series.

4. The unmanned aircraft of claim 1, wherein the charging device comprises at least one charger that is configured to be driven by exhaust gas energy.

5. The unmanned aircraft of claim 1, wherein the at least one mechanical charger is driven by an output shaft of the internal combustion engine or through an electric motor.

6. The unmanned aircraft of claim 1, wherein the controller is configured to control switching on and off of a first or second stage of the engine charging or the switching on and off of the electric motor, in accordance with at least one of the parameters of altitude, angle of a takeoff or landing flight to the vertical, desired velocity, allowable heat output, allowable operating noise level, or temperature.

7. The unmanned aircraft of claim 1, wherein the internal combustion engine is a rotary piston engine.

8. The unmanned aircraft of claim 1, wherein the aircraft has a maximum takeoff weight of more than 250 kg.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) Embodiments of the invention shall be made more apparent below with reference to the accompanying drawings.

(2) FIG. 1 illustrates a schematic representation of a first embodiment of an unmanned aircraft with propulsion;

(3) FIG. 2 illustrates a schematic representation of a second embodiment of an unmanned aircraft with propulsion;

(4) FIG. 3 illustrates a schematic representation of a third embodiment of an aircraft with propulsion;

(5) FIG. 4 illustrates a schematic representation of a first embodiment of propulsion for the unmanned aircraft according to FIGS. 1 to 3;

(6) FIG. 5 illustrates a schematic representation of the first embodiment of the propulsion, in a first operating mode;

(7) FIG. 6 illustrates a schematic representation of the first embodiment of the propulsion according to FIG. 4, in a second operating mode;

(8) FIG. 7 illustrates a schematic representation of the first embodiment of the propulsion according to FIG. 4, in a third operating mode;

(9) FIG. 8 illustrates a schematic representation of a second embodiment of the propulsion for one of the unmanned aircraft according to FIGS. 1 to 3;

(10) FIG. 9 illustrates a schematic representation of the second embodiment of the propulsion according to FIG. 8, in a first operating mode;

(11) FIG. 10 illustrates a schematic representation of the second embodiment of the propulsion according to FIG. 8, in a second operating mode;

(12) FIG. 11 illustrates a schematic representation of the second embodiment of the propulsion according to FIG. 8, in a third operating mode;

(13) FIG. 12 illustrates a schematic representation of a third embodiment of a propulsion for one of the unmanned aircraft according to FIGS. 1 to 3;

(14) FIG. 13 illustrates a schematic representation of the third embodiment of the propulsion from FIG. 12, in a first operating mode;

(15) FIG. 14 illustrates a schematic representation of the third embodiment of the propulsion from FIG. 12, in a second operating mode;

(16) FIG. 15 illustrates a schematic representation of the third embodiment of the propulsion from FIG. 12, in a third operating mode;

(17) FIG. 16 illustrates a schematic representation of the third embodiment of the propulsion from FIG. 12, in a fourth operating mode;

(18) FIG. 17 illustrates a schematic representation of the third embodiment of the propulsion from FIG. 12, in a fifth operating mode; and

(19) FIG. 18 illustrates a schematic diagram for representing a control of the propulsion of the unmanned aircraft on the basis of different parameters in flight operation.

DETAILED DESCRIPTION

(20) Three different embodiments of unmanned aircraft 10 are represented schematically, with a relevant propulsion 12, in FIGS. 1 to 3. The unmanned aircraft 10 are also called drones or (in the technical terminology) UAVs. They are a part of a system for unmanned aviationcalled a UASwith which military and civilian operations, and in particular reconnaissance flights, surveillance functions, or measurement functions, can be performed. Other than the depicted unmanned aircraft 12, the UAS also has system components that are not shown here but are well known, such as, for example, the ground-based control station with which the UAV can be remotely operated, and corresponding communication devices for communication between the unmanned aircraft 10 and the control station. For further details on UASs, reference can be made to the previously made publication, Reg Austin's Unmanned Aircraft SystemsUAS design, development and deployment published by Wiley in 2010.

(21) FIG. 1 depicts a first UAV 14 which is provided in the form of an engine-operated glider having fixed wings 16, an ordinary empennage 18, and a thrust generator, here in the form of a propeller 20, e.g., on the vertical stabilizer 22. The construction of this first UAV 14 is based on the construction of the glider e-Genius, provided with an electric auxiliary propulsion, which was developed by the University of Stuttgart's Institute of Aircraft Design and completed its maiden flight on 25 May 2011.

(22) Unlike the known e-Genius touring motor glider with electric propulsion, the first UAV 14 is, in contrast, not equipped with a passenger cockpit; rather, the space that had been developed for the pilot and a passenger is provided in order to house UAS components and the payload thereof for performing the desired UAV mission.

(23) The second UAV 24 depicted in FIG. 2 is a helicopter version of a UAV, which can likewise be propelled with the propulsion 12. Here, a rotor 25 or a rotor 25 and a tail rotor is/are provided as the thrust generator 18.

(24) The third UAV 26 depicted in FIG. 3 is another example of an unmanned aircraft 10, using the example of a tiltwing aircraft (a tiltwing and tiltrotor configuration). In this third UAV 26, the propulsion 12 is used to drive the thrust generator 18 in the form of tiltrotors 27.

(25) Different embodiments for the propulsion 12 shall be made more apparent below with reference to FIGS. 4 to 17.

(26) In all three of the different embodiments of the propulsion 12 depicted here, the propulsion is provided with an internal combustion engine 28 designed for diesel and/or kerosene operation and a charger device 30 for charging the internal combustion engine 28.

(27) The propulsion 12 is furthermore a hybrid propulsion 32 in all three of the embodiments depicted here. The hybrid propulsion 32 comprises an electrical machine 23 in addition to the internal combustion engine 28. The electric machine 34 can be used as an electric motor 36 in one type of operation, which is indicated by the letter M in the drawings, and can be used as an electrical generator 38 in another type of operation, which is indicated by the letter G in the drawings. In additional embodiments not depicted in greater detail here, the electrical machine 34 may be either an electric motor or a generator. In further embodiments that shall be described in greater detail below, a separate electric motor 36,M and a separate generator 38,G are provided.

(28) The hybrid propulsion 32 further comprises an electric energy storage device 40, which is designed, for example, as an arrangement of rechargeable battery cells or as an accumulator arrangement, and is identified also with a B in the drawings. The electrical machine 34 is connected to the electric energy storage device 40,B via power electronics 42.

(29) In the illustrated embodiments, the hybrid propulsion 32 is configured as a parallel hybrid, it being optionally possible to use the internal combustion engine 28 or the electric motor 36 to propel the unmanned aircraft 10, or possible to use both the internal combustion engine 28 and the electric motor together to propel the unmanned aircraft. To this end, a shiftable coupling device 44 is provided, with which the internal combustion engine 28 and the electrical machine 34 can selectively be coupled to an output shaft 62 connected to the thrust generator 18.

(30) The shiftable coupling device 44 comprises a first coupling 46 for coupling the internal combustion engine 28 and a second coupling 48 for coupling the electrical machine 34. The coupling device 44 and the charger device 30 can be controlled (see FIGS. 1 to 3) in accordance with a variety of parameters during flight operation, as shall be described in greater detail below. Coupling refers here to a general term for devices with which torque can be selectively transmitted (when the coupling is engaged) or shut down (when the coupling is disengaged).

(31) As can be further seen in FIGS. 4 to 17, the charger device 30 comprises at least a first charger 52 for charging the internal combustion engine 28. The first charger 52 may be configured as an exhaust gas turbocharger 54 for making use of the exhaust gas energy for the purpose of charging.

(32) In particular, the charger device 30 comprises a compressor 56 for generating pressure, in order to deliver combustion air at elevated pressure to the internal combustion engine 28.

(33) The compressor 56 can be coupled to a first exhaust gas turbine 58, so as to form the exhaust gas turbocharger 54 as the first charger 52.

(34) The internal combustion engine 28 comprises a rotary piston engine 60, in a preferred design. The rotary piston engine 60 is in particular configured in such a manner as is described and illustrated in German patent application DE 10 2012 101 032.3, and is accordingly designed for operation with diesel or kerosene. Depending on the desired power level for the UA 14, 24, 26, the rotary piston engine 60 is configured as a single-rotor rotary piston engine, a two-rotor rotary piston engine, a three-rotor rotary piston engine, or a multi-rotor rotary piston engine. The configuration of the rotary piston engine 60 comprises a special ability for modularity, for this purpose, so that one or a plurality of rotors can be provided at low cost.

(35) Whereas the foregoing is a description the common elements of the embodiments of the propulsion 12 depicted here, the following addresses the differences between the embodiments depicted here in greater detail.

(36) FIGS. 4 to 7 illustrate a first embodiment for the propulsion 12, with a single-stage charging, wherein only the first charger 52 is depicted, in the form of the exhaust gas turbocharger 54 with the compressor 56,C and the first exhaust gas turbine 58,T connected to the compressor 56. The internal combustion engine 28 and the electrical machine 34 can optionally be connected to the output shaft 62 and thus to the thrust generator 18 via the first coupling 46 and the second coupling 48.

(37) The propulsion 12 thus includes the internal combustion engine 28, which may be configured as a diesel engine and as a Wankel engine and is provided with a charging system in the form of the charger device 30 having the compressor 56 and the first exhaust gas turbine 58. The engine output shaft 64 can be connected to the thrust generator 18 via the first coupling 46. The generator 38 and the electric motor 36 oras depicted herethe electrical machine 34 able to operate as a generator G or as an electric motor M are connected via an electronic control unitthe power electronics 42,Eto a backup batterythe electric energy storage device 40,Bwhich is alternately charged during generator operation or is used to supply electrical energy to the electrical machine 34 in electric motor operation.

(38) FIG. 5 illustrates a first operating mode in which the hybrid propulsion 32 is operated in pure electric operation. For this purpose, the first coupling 46 is disengaged and the second coupling 48 is engaged.

(39) FIG. 6 illustrates the conventional operation, in which the propulsion power of the hybrid propulsion 32 is provided solely through the internal combustion engine 28. For this purpose, the first coupling 46 is engaged and the second coupling 48 is disengaged.

(40) In the third operating mode, illustrated in FIG. 7, both the first coupling 46 and the second coupling 48 are engaged, and thus both the internal combustion engine 28 and the electrical machine 34 are connected to the output shaft 62 and therefore also to one another. In this third mode, it is possible to perform an electric booster function when the electrical machine is operating as the electric motor Mthus increasing the system performance through additional electric energyor to perform a charging operation during the generator function G of the electrical machine 34.

(41) Thus, through the illustrated configuration of the first embodiment of the hybrid propulsion 32, as depicted in FIGS. 4 to 7, at least the four following operating states are possible:

(42) a) Conventional operation: The internal combustion engine 28 drives the thrust generator 18, while the generator G and the electric motor M are decoupled. This corresponds to the operating mode of existing UAV propulsion systems based on internal combustion engines.

(43) b) Electric boost: In addition to the internal combustion engine 28, the electric motor M is also coupled to the output shaft 62. This makes it possible to transmit an additional torque to the output shaft 62, thus making additional power available for a brief timedepending on the capacity of the electric energy storage device 40and accordingly enabling compensation for peaks in the power demand.

(44) c) Charging mode: In operating phases which do not require the entire engine power of the internal combustion engine 28 for the thrust generator 18, a portion of the available power can be delivered to the generator G, in order to re-charge the electric energy storage device 40.

(45) d) Purely electric operation: In addition to the operating modes above, the internal combustion engine 28 can also be decoupled and turned off, in order to switch to a purely electric operation. Here, the electric motor E is then coupled to the output shaft, which is supplied with electric energy from the electric energy storage device B.

(46) This offers, in particular, the following advantages:

(47) The function of a parallel hybrid allows for purely electric operation to reduce the thermal and acoustic signature in critical mission phases. At the same time, in conventional operation the high energy storage density of fossil fuels can be exploited, in order to achieve ranges that are not available through pure electric propulsion. In addition, the system offers the possibility of charging batteries in flight, whereby an efficient operating state of the internal combustion engine 28 can be selected through a load point increase of the internal combustion engine 28.

(48) FIGS. 8 to 11 illustrate a second embodiment of the hybrid propulsion 32. This second embodiment corresponds essentially to the first embodiment except for the difference that in addition to the first exhaust gas turbine 58, the second embodiment also comprises a second exhaust gas turbine 66,T, which is or can be coupled to the engine output shaft 64 and/or the output shaft 62.

(49) The second exhaust gas turbine 66 makes it possible for the exhaust gas energy of the internal combustion engine 28 to be exploited in two stages. In the first exhaust gas turbine 58,T, the exhaust gas energy is used by the compressor 56,C for charging the internal combustion engine 28. In the second exhaust gas turbine 66, the remaining exhaust gas energy is used for further propulsion.

(50) This makes it possible, in contrast to the first embodiment, to lower the exhaust gas temperature and thus reduce the thermal signature of the unmanned aircraft 10.

(51) The functionality of the second embodiment of the hybrid propulsion as illustrated in FIGS. 8 to 11 otherwise corresponds to that of the first embodiment of the hybrid propulsion 32, as illustrated in FIGS. 4 to 7. Accordingly, FIG. 9 illustrates the first operating mode for the pure electric operation, FIG. 10 illustrates the second operating mode for the conventional operation, and FIG. 11 illustrates the third operating mode in which either the electric boost can be performed or the charging operation can be performed. For further details of these three operating modes, reference is made to the above implementations with respect to the first embodiment.

(52) FIGS. 12 to 17 illustrate a third embodiment of the hybrid propulsion 32, as an example of the propulsion 12 for the UAVs 14, 24, 26, wherein identical or corresponding elements bear identical reference numerals as in the first two embodiments and reference can be made to the above statements for further details.

(53) In this third embodiment, the charger device 30 is configured for switchable multi-stage charging and comprises the first charger 52 and a second charger 70 for providing the multi-stage charging, wherein the different chargers 52, 70 can be switched on or switched off under the control of the controller 50 in order to switch the different stages of charging on or off.

(54) In the third embodiment of the hybrid propulsion 32, at least one electric motor 36,M and one generator 38,G are represented here in place of the electrical machine 34, which can operate in both the electric motor operation and the generator operation. The coupling device 44 comprises the first coupling 46 for coupling the engine output shaft 64 to the output shaft 62, the second coupling 48 for coupling the electric motor 36,M to the output shaft 62, and a third coupling 72 for coupling the generator 72 to the engine output shaft 64.

(55) Furthermore, a charger coupling device 74 is provided, in order to switch the charger device 30, and in particular to couple or decouple the first charger 52 and/or the second charger 70.

(56) The compressor 56 having the first exhaust gas turbine 58 is provided in order to form the first charger 52.

(57) Next, a mechanical charger 76 is provided as the second charger 70. The mechanical charger 76 may use, for example, the compressor 56 and a mechanical propulsion source. For this purpose, a first design or first charging mode makes use of an electric propulsion and in particular the electric motor 36,M. A second implementation or second charging mode makes use of the movement of the engine output shaft 64 for this purpose.

(58) In the embodiment illustrated in FIG. 12, schematically, the compressor 56,C is represented as a pressure generator that can be coupled to the first exhaust gas turbine 58 through a first charger coupling 78 of the charger coupling device 74 in order to form the exhaust gas turbocharger 54 as a first charger 52, and can be coupled to the electric motor 36,M through a second charger coupling 80 of the charger coupling device 74 in order to form the electrically operated mechanical charger 76 and, if necessary, can be coupled to the engine output shaft 64 through a third charger coupling 82 of the charger coupling device in order to form the mechanical charger 76 that can be driven by the movement of the output shaft.

(59) In the implementation depicted, simply the second coupling 48 of the switchable coupling device 44 is indicated as the third charger coupling 82.

(60) FIGS. 13 to 17 depict five different operating modes for this third embodiment of the hybrid propulsion 32. In the operating mode of FIG. 13, the first charger coupling 78 is engaged such that the first charging stage is active. The internal combustion engine 28, being charged with the first stage, is connected to the thrust generator 18 through the engaged first coupling 46. The generator 38,G is connected, as necessary, to the engine output shaft 64 through the engaged third coupling 72. Therefore, the first operating mode illustrated in FIG. 13 corresponds to charging operation, where thrust is produced via the internal combustion engine 28 being charged on the first stage, and excess power is used to charge the electric energy storage device 40. The second coupling 48 and the second charger coupling 80 are disengaged such that the electric motor 36 is connected neither to the charger device 30 nor to the thrust generator 18.

(61) FIG. 14 illustrates the electric operation, as the second operating mode. For this purpose, the second charger coupling 80 is disengaged and the electric motor is connected through engagement of the second coupling 48 to the output shaft 62 and therefore the thrust generator 18. The first coupling 46 and the third coupling 72 are disengaged such that neither the internal combustion engine 28 nor the generator is connected to the output shaft 62. The internal combustion engine 28 can be switched off here.

(62) The third operating mode illustrated in FIG. 15 corresponds to the conventional operation in single-stage charging, purely with the exhaust gas turbocharger 54. For this purpose solely the first coupling 56 and the first charger coupling 78 are engaged, and all other couplings are disengaged.

(63) FIG. 16 illustrates a fourth operating mode in the form of an operation purely with the internal combustion engine 28, which is instead charged by the second charger 70 (electric charging). For this purpose, the first coupling 46 and the second charger coupling 80 are engaged and all other couplings are disengaged.

(64) FIG. 17 illustrates a fifth operating mode in which the electric boost is presented as an additional functionality. For this purpose, the internal combustion engine 28 (the exhaust gas turbocharger 54 being active) having undergone single-stage charging is connected to the thrust generator 18; in addition, the electric motor 36 is still connected to the thrust generator 18, as well. The first coupling 46 and the second coupling 48 as well as the first charger coupling 78 are engaged, and all other couplings are disengaged.

(65) It shall be readily understood that other operating modes are possible through various switches made with the various couplings 46, 48, 72, 78, 80, 82.

(66) In the third embodiment of the hybrid propulsion 32 illustrated in FIGS. 12 to 17, the propulsion 12 has an internal combustion engine (a diesel engine/Wankel engine) having a charging system (charger device 30) comprising the compressor 56 and the exhaust gas turbine 58. The compressor 56 of the charger device 30 can, in this case, be propelled via a coupling system (charger coupling device 74) either by the exhaust gas turbine 58 or an electric motor, e.g., the electric motor M of the hybrid system. The engine output shaft 64 of the internal combustion engine 28 can be directly connected to the thrust generator 18 (e.g., a propeller 20 or rotor 25, 27). In addition, the electrical generator 38,G is to be connected to the engine output shaft 64 and/or the output shaft 62 via a separate coupling (third coupling 72). The generator 38,G and the electric motor 36,M are connected via an electronic control unit (power electronics 42,E) to a backup battery (an example of the electric energy storage device 40,B) which alternately is charged by the generator 38,G or is to be used for supply to the electric motor 36,M.

(67) The construction illustrated in FIGS. 12 to 17 enables, in particular, the following four operating states:

(68) a) Conventional operation: The compressor 56 of the exhaust gas turbocharger 54 is propelled by the exhaust gas turbine 58 of the charger device 30, while the electric motor 36,M and generator 38,G are decoupled. This corresponds to the operating mode of existing conventional propulsion systems, but with the difference of diesel or kerosene operation with additional charging.

(69) b) Electric turbo: The compressor 56 of the charger device 70 is in this case propelled by the electric motor 36,M. This allows a greater increase in power to be generated than would take place in coupling of the electric motor 36,M to the output shaft 62.

(70) c) Electric boost: Here, in addition to the power of the internal combustion machine, the power of the electric motor 36,M is also transmitted to the output shaft 62.

(71) d) Charging mode: In operation phases where not all of the engine power of the internal combustion engine 28 is required by the thrust generator 18, then a portion of the available power can be delivered to the generator 38,G, in order to re-charge the battery (electric energy storage device 40,B). The compressor 56 of the charger device 30 is in this case driven by the exhaust gas turbine 58 while the electric motor 36,M is decoupled.

(72) This offers, in particular, the following advantages.

(73) In addition to the functionality of a parallel hybrid (operation with an internal combustion machine, purely electric operation, or recharging of the battery), the electric motor 36,M can be used in two ways in order to make additional power available:

(74) a) through an electric boost in which the power is directly fed to the output shaft 62, or

(75) b) through an electrically driven mechanical charger 76, with which the required power for charging is provided by the electric motor 36,M and need not interfere with the process of the internal combustion engine. This is advantageous in that, in contrast to propulsion with an exhaust gas turbine 58, no back pressure is built up in the exhaust gas, against which the internal combustion engine 28 would otherwise need to work. In contrast to the use of a mechanical propulsion for the mechanical charger 76in particular, through coupling to the engine output shaft 64there is no need to detract any mechanical power of the output shaft.

(76) Different embodiments of the hybrid propulsion 32 are presented above, with reference to the drawings. It shall be readily understood that further embodiments are also possible, but these are not shown here. For example, the second exhaust gas turbine 66 may also be present in the embodiment illustrated in FIGS. 12 to 17, and in particular may be switchable via a separate switching device that can switch this second exhaust gas turbine 66 on or off.

(77) Furthermore, either in addition to or alternatively to the propulsion of the mechanical charger 76 through the electric motor 36 of the hybrid propulsion, it would also be possible to have a separate electric motor for the propulsion of the compressor. On the other hand, it would also be possible to drive the compressor 56 via the engine output shaft 64. Moreover, instead of the depiction with only one compressor 56, it would also be possible to provide a plurality of compressors, which can be driven via the first exhaust gas turbine 58, the second exhaust gas turbine 66, the electric motor 36 of the hybrid propulsion 32, and/or through the engine output shaft 64.

(78) A possible control of the hybrid propulsion 32 for the unmanned aircraft 10 shall be described in further detail below, with reference to the illustration in FIG. 18.

(79) As illustrated in FIGS. 2 and 3, the unmanned aircraft 10 may be a UAV 24, 26, which is capable of vertical takeoff and landing (VTOL), and/or a UAV 14, 26, which is capable of a convention takeoff and landing as with an airplane (making use of the flow of air during travel of the aircraft 10 (CTOL)).

(80) The diagram in FIG. 18 illustrates the required power P over the flight velocity v. The arrow R indicates the range of cruising flightthe cruising range. ISA stands for the international standard atmosphere.

(81) The curve S shows the power needed for various flight conditions at sea level and at standard atmospheric conditions; the curve H1 shows the power needed at high altitudes and standard atmospheric conditions, and the curve H2 shows the power needed at higher altitudes and at standard atmospheric conditions elevated by approximately 15 C.

(82) The various operating modes provide coverage for all of the power ranges that are required with these various operating conditions and flight conditions.

(83) The controller switches through the various operating modes, in particular the switching on or off of the charger device or the switching on or off of various chargers or various stages of charging, in accordance with parameters that are indicative of these operating conditions, such as the target/actual velocity, altitude (in particular, as can be detected via pressure sensors), desired VTOL or CTOL, or temperature.

(84) The power stages L represented in the drawings, which can be switched on or off by the control, denote the maximum available power for:

(85) L1 internal combustion engine operation without charging;

(86) L2 internal combustion engine operation with charging in a first stagein particular, operation of the first charger 52, i.e., of the exhaust gas turbocharger 54;

(87) L3 internal combustion engine operation with charging in the second stagefor example, operation of the second charger 70, such as in particular of the electrically drive mechanical charger 76;

(88) L4 internal combustion engine operation with charging in the second stage and additionally with the electric boost function.

(89) The engine charging increases the available engine power of the internal combustion engine 28. This allows in particular for vertical takeoffs at higher altitudes and/or at higher ambient temperatures (hot and high conditions). This further increases the maximum cruising velocity.

(90) The possibility of the electric boost further increases the available power for such conditions, where the limit of the power increase is reached through engine charging. This makes it possible to further extend the application areas. For example, vertical takeoffs at even higher altitudes and at even higher temperatures are possible; a maximal cruising velocity in difficult conditions can also be further increased.

(91) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

REFERENCE SIGNS LIST

(92) 10: unmanned aircraft; 12: propulsion; 14: first UAV; 16: wing; 18: thrust generator; 20: propeller; 22: vertical stabilizer; 24: second UAV; 25: rotor; 26: third UAV; 27: tiltrotor; 28: internal combustion engine; 30: charger device; 32: hybrid propulsion; 34: electrical machine; 36,M: electric motor; 38,G: generator; 40,B: electric energy storage device; 42,E: power electronics; 44: switchable coupling device; 46: first coupling; 48: second coupling; 50: controller; 52: first charger; 54: exhaust gas turbocharger; 56: compressor; 58: first exhaust gas turbine; 60: rotary piston engine; 62: output shaft; 64: engine output shaft; 66: second exhaust gas turbine; 70: second charger; 72: third coupling; 74: charger coupling device; 76: mechanical charger; 78: first charger coupling; 80: second charger coupling; 82: third charger coupling; S: sea level; R: cruising range; v: forward speed; P: power; H1: high altitude, at ISA; H2: high altitude, at ISA+15 C.; ISA: standard atmosphere; VTOL: vertical takeoff/landing; CTOL: conventional takeoff/landing; L1: internal combustion engine operation without charging; L2: internal combustion engine operation with charging, first stage; L3: internal combustion engine operation with charging, second stage; L4: internal combustion engine operation with charging, second stage+electric boost