Aerial drive device, aircraft and method of operating an aerial drive device

Abstract

The invention relates to an aviation drive (3) for an aircraft (1), having: - a propeller (4), which is arranged on a drive shaft (5) of the aviation drive (3) and can be driven about an axis of rotation (6) of the propeller (4) by means of the drive shaft (5), - a propeller dome (8), which is arranged in a front region (10) of the propeller (4) viewed in the direction (9) of the axis of rotation (6) of the aviation drive (3), - a propeller dome adjustment device (12) for definably changing the volume of the propeller dome (8) in the radial direction (13) with respect to the axis of rotation (6). Furthermore, the invention relates to an aircraft (1) having at least one aviation drive (3) and to a method for operating an aviation drive (3).

Description

Technical Field

[0001] This invention relates to an aircraft propulsion device for an aircraft, the propulsion device having a propeller arranged on a drive shaft and capable of being driven about the propeller's axis of rotation by means of the drive shaft. Furthermore, the aircraft propulsion device has a propeller fairing arranged in a region of the propeller located at the front when viewed along the axis of rotation of the aircraft propulsion device.

[0002] Furthermore, the present invention relates to an aircraft having at least one aviation drive unit. The invention also relates to a method for operating the aviation drive unit of an aircraft, wherein a propeller of the aviation drive unit, arranged on a drive shaft of the aircraft, is driven by the drive shaft about the rotation axis of the propeller. Background Technology

[0003] For example, developing "Personal Air Vehicles" (PAVs) or flight equipment capable of vertical takeoff and landing (eVTOL "Electric Vertical Takeoff and Landing Vehicles") for future mobility solutions. In this approach, a common propeller can be used for both vertical takeoff and cruise flight. For example, a "tilt-wing" or "opportunistic rotor" configuration could be applied. Unlike the "lift and cruise" configuration, in these configurations, a separate engine-propeller unit can be used for both takeoff and cruise (Reiseflug), thus minimizing the mass of the flight equipment.

[0004] The efficiency of the propeller has a significant impact on the stroke length of such flight equipment, especially the electric stroke length. However, for these designs, the propeller design usually embodies a trade-off, as it must be adapted to both hovering flight (hovering or takeoff) and cruise flight. For example, variable-pitch propellers are used in batches in classic aircraft. In these variable-pitch propellers, the individual propeller blades rotate synchronously about their longitudinal axis and are thus adapted to the corresponding flight conditions. Therefore, good efficiency can be achieved both during takeoff (before the aircraft motion generates headwind speed) and during cruise flight (when headwind speed is generated by flight speed).

[0005] For example, the prior art discloses a variable propeller pinner for targeted influence on the cooling airflow for an internal combustion engine located thereafter. The prior art also discloses a propeller pinner optimized for aircraft with a "tilt rotor configuration".

[0006] Patent document US 2020 / 0 223 552A1 discloses, for example, a rotor assembly for use in an aircraft. This rotor assembly includes a rotor hub, a main shaft structure including a fairing opening, and rotor blades. The rotor blades have a rotor root located near the rotor hub. The rotor assembly also includes a movable panel surface at least partially mounted along the rotor hub.

[0007] The drawback is that, especially since the rotor blades rotate as a whole, but the airflow conditions near the hub (small radius) and near the blade tip (large radius) are different, this represents a compromise that does not fully utilize the propeller's efficiency. Variations in engine speed and angle of attack also offer only a limited number of possibilities (degrees of freedom) to improve efficiency. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to improve the efficiency of aircraft drive devices, especially the efficiency of propellers.

[0009] The technical problem is solved according to the present invention by an aviation drive device for an aircraft, an aircraft, and a method for operating the aviation drive device for an aircraft.

[0010] One aspect of the present invention relates to an aircraft propulsion device for an aircraft, the aircraft propulsion device having:

[0011] - A propeller, which is mounted on the drive shaft of an aircraft drive unit and can be driven by the drive shaft about the propeller's axis of rotation.

[0012] - A propeller fairing, which is arranged in the forward region of the propeller when viewed along the axis of rotation of the aircraft drive unit.

[0013] - A propeller fairing adjustment device, which is used to change the volume of the propeller fairing radially relative to the axis of rotation as defined or specified.

[0014] The aircraft drive device according to the invention can, for example, operate aircraft or flight equipment more efficiently. The efficiency of the propeller can be improved by changing the volume of the propeller fairing by means of a propeller fairing adjustment device. Compared with propellers in the prior art, an efficiency improvement of 10%, particularly 20%, especially 25%, can be achieved here.

[0015] The flight range of an aircraft during cruise flight can be increased by means of the aviation drive system according to the invention. This is achieved through the improved efficiency of the aviation drive system. With a more efficient aviation drive system, the aircraft can, for example, carry a greater payload. In particular, the payload capacity of the aircraft can be increased by means of the aviation drive system according to the invention while keeping the flight range constant.

[0016] In particular, a variable propeller fairing for an aircraft can be provided using a propeller fairing adjustment device. With propellers in the prior art, for example, during the cruise flight of an aircraft, localized downward drive (abtrieb) rather than lift (propeller thrust) may occur primarily near the propeller hub. Therefore, near the hub, the propeller blades tend to brake rather than drive the aircraft. Although, for example, averaging over the propeller radius still yields a positive propeller thrust as lift, efficiency is lost. These disadvantages can be overcome, for example, by changing the volume of the propeller fairing according to the invention, thereby isolating or covering these disadvantageous areas, for example, near the hub. This can improve the efficiency of the propeller, especially the aircraft drive system. The propeller fairing can be, in particular, one whose size or volume can be dynamically adjusted, which can be changed or varied by means of a propeller fairing adjustment device so that, for example, areas of the propeller that impair efficiency can be covered or isolated. This can improve the overall efficiency of the aircraft's cruise flight.

[0017] In particular, the propeller fairing adjustment device can be used to change or adapt (or adjust) the volume or diameter of the propeller fairing according to a definition, thereby improving the efficiency of the aircraft's propulsion system and aircraft during cruise flight.

[0018] An aircraft can be, for example, a vertical takeoff and landing (VTOL) aircraft, which can be described as an aircraft capable of taking off and landing vertically. VTOL aircraft are particularly capable of changing flight modes (flight states) during flight. For example, hovering in helicopter mode, followed by a transition from vertical to horizontal flight, and horizontal flight (corresponding to a fixed-wing aircraft) are considered relevant flight states of a VTOL aircraft.

[0019] An aircraft propulsion system can be, for example, a tiltrotor. An aircraft can be designed as a tilt-wing aircraft.

[0020] This aircraft is specifically a "vertical take-off and landing aircraft" (eVTOL). Therefore, the aforementioned aviation propulsion system can be used in aircraft designed in this way. The aircraft can, for example, be a component of urban air transportation, such as an air taxi.

[0021] This aircraft is particularly capable of vertical takeoff and vertical landing.

[0022] The propeller can be, in particular, an air propeller for an aircraft. A propeller can, for example, generate shaft power or forward thrust or force from an aircraft engine or a shaft turbine.

[0023] The propeller can be designed as a variable-pitch propeller, where the angle of attack of the propeller blades can be varied, thus adapting the angle of attack to different operating conditions of the aircraft. A drive shaft drives both the propeller and the rotation axis, allowing the propeller to be positioned at a preset rotational speed. The drive shaft can, for example, be constructed parallel to the rotation axis.

[0024] A propeller fairing can be a fairing used in aviation, which can be a streamlined panel located in front of the propeller at the center of the propulsion unit of an aircraft, or it can be a streamlined panel in a turbofan engine. Propeller fairings are used, for example, to reduce air resistance and thereby improve the airflow response of the aircraft's propulsion unit.

[0025] An aircraft propulsion device may be referred to as the propulsion device or propulsion unit of an aircraft.

[0026] For example, a propeller fairing can be used to at least regionally, and especially completely, cover the propeller tip. The propeller fairing can, for example, reach the cowling of an aircraft engine or propulsion unit. Such a cowling for an aircraft engine can, for example, be called an engine cowling or propulsion unit nacelle.

[0027] Specifically, the propeller fairing adjustment device can be electromechanical or mechanical. For example, the propeller fairing adjustment device can be operated and / or adjusted by means of control and / or regulation devices to change the volume of the propeller fairing. The change, adaptation, or adjustment of the propeller fairing volume is particularly automatic.

[0028] Changes in volume are achieved, in particular, based on the flight attitude (flugstellung) of the aircraft's propulsion system or aircraft.

[0029] Alternatively, the propeller fairing can be radially enlarged by means of a propeller fairing adjustment device, thereby changing its volume. The volume of the propeller fairing is hereby specifically increased radially or widened radially.

[0030] If necessary, the volume of the propeller fairing can be expanded by means of a propeller fairing adjustment device as defined.

[0031] Changing the volume of the propeller fairing specifically refers to intentionally adjusting or altering its volume. The volume of the propeller fairing can be changed, particularly at the system level. This allows for variable control over the change in the propeller fairing's volume.

[0032] With the aircraft drive device according to the invention, the disadvantages of using the same propeller for vertical takeoff or for hovering and cruise flight can be minimized or suppressed.

[0033] In one embodiment, the propeller fairing adjustment device allows the volume of the propeller fairing to be changed from a basic state to at least one expanded state, such that the propeller's leading edge is at least regionally covered forward by the volume-changed propeller fairing to a greater extent than in the basic state, particularly by the propeller fairing covering the propeller's leading edge at least regionally on the side of the propeller facing the propeller. The volume of the propeller fairing can be automatically changed from the basic state to at least one expanded state, for example, by means of the propeller fairing adjustment device according to the adjustment amount. For example, in at least one expanded state, the volume of the propeller fairing is wider or larger compared to the volume of the propeller fairing in the basic state. In the expanded state, the volume of the propeller fairing is particularly larger or wider compared to the volume of the propeller fairing in the basic state.

[0034] The volume of the propeller fairing can be varied variably from its basic state. In particular, the volume in the expanded state can be gradually widened, enlarged, or expanded.

[0035] In the basic configuration, the volume of the propeller fairing is not altered by the propeller fairing adjustment device. In the basic configuration, the volume of the propeller fairing is not changed or affected by the propeller fairing adjustment device.

[0036] For example, the volume can be adjusted from multiple possible expansion states to form an expansion state adapted to the corresponding situation or condition, depending on the attitude of the aircraft's propulsion system or the flight stage of the aircraft. In particular, different expansion states can be formed. The volume of the propeller fairing can thus be transformed from a basic state to an expansion state adapted to the corresponding situation.

[0037] In the expanded state, the propeller's leading edge surface can be at least regionally, especially locally, and preferably completely covered or isolated by means of the expanded propeller fairing. Since the volume of the propeller fairing expands or enlarges in at least one expanded state compared to the basic state, the propeller's leading edge surface can be covered over a smaller or larger area compared to the basic state. This can be done dynamically using a propeller fairing adjustment device.

[0038] In the expanded state, the internal propeller region (relative to the axis of rotation) can be at least regionally covered or isolated, thereby minimizing potential adverse characteristics for the aircraft's flight operation in that region. In particular, isolating or covering the propeller's leading surface can slow down at least one flow velocity in the covered region, resulting in little or no braking effect. This can improve or increase the propeller's efficiency or overall efficiency during the aircraft's cruise flight.

[0039] The region or side of the propeller extending toward the propeller fairing can be covered, at least regionally, by a change in volume. The side or region of the propeller fairing facing or pointing toward the propeller can at least regionally cover the propeller's forward surface. The propeller's forward surface can be, for example, the forward-pointing side of the propeller along the longitudinal direction of the aircraft drive. The side of the propeller fairing facing the propeller can be, in particular, the side that rests against the propeller and extends, especially toward the propeller's center point.

[0040] By at least partially covering the propeller's leading edge surface, unfavorable headwinds in the propeller region near the hub during cruise flight can be prevented or reduced. This prevents the generation of only small thrust but unfavorable drag ("dragging"). Especially in various operating conditions of the aircraft, thrust can even be negative at higher flight speeds, so the internal parts of the propeller can suppress airflow. This can also be minimized or reduced by at least partially covering the propeller's leading edge surface. This results in higher efficiency during cruise flight, as energy consumption is reduced and travel length is increased. Furthermore, lower acoustic loads are generated both externally and internally during cruise flight.

[0041] In another embodiment, at least one radially inwardly extending radially outwardly from the axis of rotation relative to the propeller's axis of rotation is covered by the propeller fairing in its expanded state, particularly over a greater extent radially than in its basic state. Thus, the propeller region inside the propeller is at least regionally covered by the propeller fairing in its expanded state.

[0042] The radially inner partial surface of the propeller front surface corresponds, for example, 20%, especially 30%, especially 40% of the total area of ​​the propeller front surface.

[0043] The internal partial surfaces may correspond, for example, to one-third of the total area of ​​the propeller's front surface. These internal partial surfaces of the propeller's front surface are particularly located in the region of the propeller hub or the rotor hub of the rotor.

[0044] By means of a propeller fairing, at least a localized area of ​​the propeller's leading surface directly along the axis of rotation can be covered in the expanded state. Specifically, the inner localized surface is the area extending from the distal end of the propeller's leading surface away from the propeller. The proportion of the inner localized surface covered can vary, in particular, depending on the adjusted expansion state. The size of the covered area within the inner localized surface of the propeller's leading surface can be determined, in particular, according to the expansion state selected by the propeller fairing adjustment device.

[0045] In one embodiment, it is further specified that, compared to the basic state, the rear end of the propeller fairing expands radially in the expanded state. Therefore, in particular, the region or side of the propeller fairing extending towards the propeller can expand radially. This allows for efficient, at least regional, coverage or concealment of the propeller's front surface, especially internal local surfaces.

[0046] For example, the axis of rotation of the propeller fairing corresponds to the axis of rotation of the propeller.

[0047] In one embodiment, the propeller is further specified to have at least two propeller blades, each blade being connected to the drive shaft at a connection point on the propeller. The respective surface regions of the at least two propeller blades extending towards the connection point and away from their respective radial end regions are at least regionally covered on the front side by a propeller fairing whose volume is altered by a propeller fairing adjustment device. The respective surface regions of the at least two propeller blades may, in particular, be located within a localized radially inward surface of the propeller's front surface. In other words, the respective surface regions of the at least two propeller blades extending within a localized radially inward surface of the propeller's front surface can be at least regionally, and especially completely, covered or isolated by means of a propeller fairing whose volume changes in the expanded state.

[0048] A propeller may have at least two, and especially more, propeller blades. Propeller blades may be referred to as blades or rotor blades, for example.

[0049] At least two propeller blades are respectively arranged at the connection point of the propeller and thus connected to the drive shaft, so that the propeller blades move or rotate around the axis of rotation at a preset speed through the rotational motion of the propeller. The connection point of the propeller is particularly the center of the propeller. The axis of rotation extends particularly through the connection point. The connection point may be referred to, for example, as a rotor hub or propeller hub or wheel hub. The connection point serves to hold or fix the rotor blades and mechanically connect the rotor to the drive shaft, so that the force generated by the drive shaft can be transmitted to the rotor, especially to the rotor blades. This is particularly used for driving aircraft, especially for propelling aircraft forward.

[0050] The corresponding radial end region of the rotor blade can be the distal end of the corresponding rotor blade. The corresponding radial end region of the rotor blade is particularly far from the connection point.

[0051] In another embodiment of the invention, it is specified that the corresponding surface area of ​​at least two propeller blades corresponds to at least 20%, particularly 30%, particularly 40%, of the corresponding propeller leading surface of at least two propeller blades. In other words, the corresponding surface area is a radially inward partial surface of the propeller leading surface, which is covered in percentage form according to the expanded state formed by the adjustment of the propeller fairing. One-third of the corresponding propeller leading surface of at least two propeller blades can be covered, for example, by means of the expanded propeller fairing. Thus, the inner propeller region extending in the region of the propeller hub is at least regionally, and particularly completely, covered in the expanded volume of the propeller fairing. The corresponding surface area of ​​at least one propeller surface can, for example, correspond to any value between 15% and 45% of the corresponding propeller leading surface of at least two propeller blades. This corresponding percentage value is adjusted according to the level or category of the expanded state of the propeller fairing.

[0052] In one embodiment, the propeller fairing is at least partially, and especially entirely, made of a material with anisotropic elasticity, and has at least one reinforcing element on its outer side, particularly along the circumference. The material of the propeller fairing, in particular, has at least partially, and especially entirely, anisotropic elastic properties. Anisotropic elastic properties should be understood as direction-dependent characteristics, particularly material properties. Therefore, the material that forms part of the propeller fairing can, for example, have different elastic properties along the corresponding directions. The propeller fairing can thus, for example, have high elasticity along the circumference and relatively low flexural elasticity along the axial or radial direction. Due to the high elasticity along the circumference, the volume of the propeller fairing can expand radially. Therefore, an increase in diameter can be achieved along the circumference. Due to the low flexural elasticity along the axial or radial direction, the propeller fairing has defined shape stability. This shape stability is particularly important during the cruise flight of an aircraft, because during flight, high, especially extreme, forces act on the propeller and, particularly, the propeller fairing positioned in front of the propeller.

[0053] Additionally or alternatively, the propeller fairing may have at least one or more reinforcing elements circumferentially on its outer side. These additional reinforcing elements ensure that the propeller fairing has a flight-stable shape both in its base state and its expanded state, thereby enabling efficient cruise flight of the aircraft. At least one reinforcing element may, for example, consist of multiple sub-elements. At least one reinforcing element is arranged, particularly circumferentially, on the outer side of the propeller fairing or on the outer casing. The material of the propeller fairing may, for example, be glass fiber reinforced polypropylene. The glass fiber reinforced polypropylene has, in particular, different elastic moduli up to approximately 3 along both spatial directions.

[0054] Furthermore, the propeller fairing material can be, for example, polyurethane (TPU). Polyurethane has high elasticity and can be reinforced, for example, with carbon fiber (CF).

[0055] The propeller fairing can, for example, have a honeycomb structure at least regionally, with the honeycomb structure exhibiting different elastic properties along different spatial directions. This structure can be achieved, for example, using anisotropic TPU-CF material.

[0056] In another embodiment, the propeller fairing's shroud (Hülle) is designed as a parabola, and in particular, the propeller fairing shroud is capable of expanding radially in a rotationally symmetrical manner about the axis of rotation. The shroud of the propeller fairing specifically refers to the outer cover or outer surface of the propeller fairing.

[0057] A parabola is a second-order surface geometry. The casing of a propeller fairing can, in particular, be designed as an elliptical parabola. The casing of a propeller fairing can, in particular, expand radially to change or enlarge the volume of the propeller fairing. The casing is hereby designed or arranged rotationally symmetrically about a rotational axis and can expand or enlarge radially. This allows the volume of the propeller fairing to be changed or widened to cover at least a localized area of ​​the propeller's leading edge.

[0058] The enclosure can be, in particular, the housing, cover structure, or panel of a propeller fairing.

[0059] Propeller fairings, in particular, can be designed to be flexible.

[0060] In one embodiment, the propeller fairing has a plurality of sheets (or slabs) as outer panels that can be adjusted by a propeller fairing adjustment device. The plurality of sheets are arranged overlapping each other along the rotation direction and around the rotation axis in the basic state of the volume of the propeller fairing. In order to change the volume of the propeller fairing, the plurality of sheets are adjusted by the propeller fairing adjustment device such that the plurality of sheets have a predetermined distance from each other.

[0061] Specifically, multiple sheets can be automatically manipulated and thereby changed, or the multiple sheets can be changed to alter the volume, using a propeller fairing adjustment device. Therefore, in one possible example, the propeller fairing can have multiple movable elements, such as multiple sheets serving as a shell or outer panel. These movable elements change their positions relative to each other in such a way that the volume of the propeller fairing can be altered.

[0062] To increase the volume of the propeller fairing, the positions or arrangement of multiple sheets are altered to create a greater distance between them. This is particularly true in the expanded state of the propeller fairing. In its basic or original state, the propeller fairing consists of multiple sheets arranged overlapping each other. To change the volume of the propeller fairing to an expanded state, the overlapping arrangement of the sheets is changed to a spaced-apart arrangement, thereby significantly expanding the volume of the propeller fairing. The arrangement of the sheets can vary depending on the type or state of expansion. This can be achieved, in particular, through a mechanical connection between the coupling parts of the sheets and the propeller fairing adjustment device. The adjustment of the sheets is achieved, in particular, automatically or automatically, using the propeller fairing adjustment device.

[0063] The sheets are arranged or positioned, particularly around the axis of rotation, in the direction of rotation or circumferentially, as the outer panels of the propeller fairing. Multiple sheets are adjusted, in particular, circumferentially, so that when viewed circumferentially, the sheets have a predetermined, and especially increased, distance from each other. In an expanded state, the multiple sheets can be arranged, for example, such that they no longer overlap. In one possible expanded state, the multiple sheets can be arranged at least regionally abutting each other at their outer edges.

[0064] In particular, it is possible to form a cup-shaped outer panel or shell for the propeller fairing using multiple sheets. In other words, multiple sheets can be opened in a fan shape for the expanded state of the propeller fairing.

[0065] The propeller fairing can be composed of multiple sheets on the outside, and the volume or size of the propeller fairing can be changed by the relative movement of the sheets relative to each other.

[0066] In one embodiment, a propeller fairing adjustment device is arranged in the internal region of the propeller fairing, wherein a movable adjustment element of the propeller fairing adjustment device is arranged on the forward side of the propeller fairing away from the propeller, and wherein the movable adjustment element is configured to move from the side away from the propeller toward the propeller within the internal region by means of the propeller fairing adjustment device to change the volume of the propeller fairing. The volume of the propeller fairing can be changed here, particularly by means of a mechanical mechanism.

[0067] The movable adjustment element can be, for example, an adjustment cone. The internal region of the propeller fairing is, for example, the internal space of the propeller fairing cavity.

[0068] Movable adjustment elements are particularly arranged within the internal region of the propeller fairing and can be controlled for movement by means of a propeller fairing adjustment device. In the basic state of the propeller fairing, the movable adjustment elements are located on the front side of the propeller fairing away from the propeller, i.e., in the region of the tip of the propeller fairing. In the expanded state of the propeller fairing, the movable adjustment elements can be manipulated and moved such that they move, in particular, from the front side of the propeller fairing away from the propeller toward the propeller, i.e., the side of the propeller fairing extending toward the propeller, towards the propeller. By moving the adjustment elements from the front side of the propeller fairing toward the rear side of the propeller fairing, a change in the volume of the propeller fairing can be produced. Thus, the volume of the propeller fairing can be adjusted by means of a mechanical adjustment mechanism to cover at least one area of ​​the front surface of the propeller.

[0069] In one embodiment, the propeller fairing adjustment device includes a pneumatic adjustment unit, wherein at least one inflatable element arranged in the internal region of the propeller fairing can be controlled by the pneumatic adjustment unit to change the volume of the propeller fairing. This allows the volume of the propeller fairing to be adjusted in the simplest way by inflating or deflating the inflatable element. In the basic state of the propeller fairing, the inflatable element is particularly in an uninflated or only partially inflated state.

[0070] In the expanded state of the propeller fairing, the inflatable components are partially, and especially fully, inflated. The inflatable components can be variably inflated depending on the expanded state and the extent to which the propeller's forward surface is covered. This can be achieved using a propeller fairing adjustment device. At least one or more inflatable components can be arranged within the internal space or region of the propeller fairing. This allows the volume of the propeller fairing to be changed using a pneumatic mechanism.

[0071] The propeller fairing can be modified in this way, either pneumatically or hydraulically.

[0072] Inflatable elements can be designed, for example, as inflatable rings arranged circumferentially within the inner region of the propeller fairing.

[0073] Another aspect of the invention relates to an aircraft having at least one aerodynamic drive designed according to the foregoing aspects or advantageous extensions thereof. According to the invention, during hovering flight, the axis of rotation of the propeller is oriented at a predetermined angle relative to the longitudinal direction of the aircraft to the vertical, and during cruise flight, the axis of rotation of the propeller is oriented at a predetermined angle relative to the longitudinal direction of the aircraft to the horizontal.

[0074] During hovering flight, the propeller's axis of rotation can be positioned, for example, within a range of ±10% relative to the vertical. During cruise flight, the propeller's axis of rotation can be positioned within a range of ±10% relative to the horizontal.

[0075] During hovering flight, the propeller's axis of rotation can optionally be arranged perpendicular to the aircraft's longitudinal direction. Furthermore, during cruise flight, the propeller's axis of rotation can optionally be oriented parallel to the aircraft's longitudinal direction.

[0076] The orientation of the propeller's rotation axis can vary, in particular, depending on the flight stage or flight status of the aircraft.

[0077] The aircraft can be, for example, a vertical takeoff and landing (VTOL) aircraft capable of taking off and landing vertically. The aircraft can, in particular, change its flight mode or flight status during flight. The aircraft can, for example, be a helicopter. The aircraft can, in particular, be designed as an eVTOL (“vertical takeoff and landing”) aircraft. The aircraft can, in particular, be referred to as an air taxi.

[0078] Aircraft can be, for example, part of a fleet of aircraft used to provide efficient maneuverability solutions.

[0079] The aircraft may have at least one aero-drive unit, and more particularly multiple aero-drive units, especially propulsion units. For example, the aircraft may have an aero-drive unit according to the invention for each wing or flap. Similarly, two aero-drive units according to the invention may be arranged for each wing.

[0080] The number of aircraft propulsion units can be determined, for example, based on the corresponding application field of the aircraft.

[0081] In particular, the trade-off described in the invention can be eliminated or minimized by means of an aircraft according to the invention, and especially by means of an aircraft drive system according to the invention. This trade-off describes the distinction between the operating state of "hovering," i.e., without control, and forward flight, i.e., with headwinds. For example, a propeller can generate usable lift near the hub, i.e., near the propeller hub, during hovering flight. During cruise flight, the propeller may generate at least partially harmful downward thrust near the hub. This may also be the case with variable-pitch propellers. For example, in the case of a variable-pitch propeller, the entire propeller blade can be adjusted to a greater extent corresponding to a higher axial headwind. The angle of attack can be changed here. This can be solved, for example, by the invention.

[0082] Another aspect of the invention relates to a method for operating an aircraft drive system, wherein a propeller of the aircraft drive system, arranged on a drive shaft, is driven by the drive shaft about a rotation axis of the propeller. According to the invention, the volume of a propeller fairing arranged in the forward region of the propeller, viewed along the rotation axis of the aircraft drive system, is changed radially relative to the rotation axis by a propeller fairing adjustment device according to the attitude of the aircraft drive system.

[0083] The methods described above can be performed, in particular, by an aircraft drive unit or aircraft designed according to the foregoing aspects or their advantageous extensions. The aircraft drive unit and / or aircraft can, in particular, have devices, especially technical devices, for implementing or performing the methods described above.

[0084] Changes in volume can be achieved automatically, especially based on the attitude of the aircraft's propulsion system or the aircraft itself.

[0085] The flight phase, flight mode, or flight state of an aircraft can be characterized, in particular, by the attitude of its aero-drive system. Here, the aircraft can, for example, perform hovering flight in helicopter mode. This occurs especially during the takeoff and / or climb phases of the aircraft. Hovering flight also occurs during descent and / or landing approach or landing. Hovering flight can be understood as a flight state in which the position and altitude of the aircraft remain unchanged in the air. Furthermore, cruise flight can be performed as a flight phase while the aircraft is moving forward or flying. For example, the flight phase between climb and the start of descent after reaching the planned cruise flight altitude can be called cruise flight. If, for example, a flight altitude for performing cruise flight is reached, the aircraft and therefore the aero-drive system are specifically set to cruise flight mode.

[0086] In one embodiment of the method described above, the volume of the propeller fairing is changed from a basic state to at least one expanded state by a propeller fairing adjustment device, such that the leading surface of the propeller is at least regionally covered forward by the volume-changed propeller fairing to a greater extent than in the basic state. This allows for the automatic adjustment, for example, of at least one of a plurality of expanded states forming the propeller fairing according to the attitude of the aircraft drive and / or the flight phase of the aircraft, thereby enabling, in particular, the expansion of the propeller fairing volume to cover at least one localized area of ​​the propeller leading surface.

[0087] In another embodiment of the above method, the volume of the propeller fairing automatically changes as the aircraft's propulsion system changes its attitude between cruise and hovering. Furthermore, the volume of the propeller fairing can be set, changed, or configured to an expanded state in cruise and to a basic state in hovering. Based on the attitude of the aircraft's propulsion system and / or the operating state of the aircraft, the timing and / or duration of changing the volume of the propeller fairing and / or the volumetric dimension to which the volume of the propeller fairing changes can be determined. This can be achieved, for example, by means of an electronic analysis unit of the propeller fairing adjustment device.

[0088] Electronic analysis units can, for example, determine or calculate the time and duration at which the propeller fairing volume should be changed. This information can be transmitted, for example, to the propeller fairing adjustment mechanism, particularly the control unit. Furthermore, the volume of the propeller fairing to be reached or changed can be determined. Different information can be considered here. The aircraft's operational state can be, for example, its flight phase. Of particular importance is whether the aircraft is in the takeoff phase or the cruise phase.

[0089] An advantageous implementation of one aspect can be regarded in particular as an advantageous implementation of another aspect and / or all aspects. An advantageous embodiment of an aircraft propulsion device can be regarded in particular as an advantageous embodiment of an aircraft and a method. An advantageous embodiment of the method can also be regarded as an advantageous embodiment of an aircraft propulsion device. This also applies to the method in the reverse manner.

[0090] The present invention also includes extended designs of the aircraft according to the invention and the method according to the invention, said extended designs having features already described in conjunction with an extended design of an aero-drive device according to the invention. Therefore, the corresponding extended designs of the aircraft according to the invention and the method according to the invention will not be described further here.

[0091] The present invention also includes combinations of features of the embodiments described. Attached Figure Description

[0092] The following describes embodiments of the present invention. In the accompanying drawings:

[0093] Figure 1 A schematic diagram of an aircraft having at least one aviation drive unit in a cruise flight attitude is shown;

[0094] Figure 2 It shows Figure 1 Another schematic diagram of an aircraft in a hovering flight attitude;

[0095] Figure 3 It shows Figure 1 A schematic diagram of an aircraft drive unit, wherein the volume of the propeller fairing of the aircraft drive unit is in its basic state;

[0096] Figure 4 It shows Figure 1 Another schematic diagram of an aircraft drive unit, in which the volume of the propeller fairing of the aircraft drive unit is in an expanded state;

[0097] Figure 5 An exemplary side sectional view of the propeller fairing shows a mechanism for changing the volume of the propeller fairing (shown here in the basic state).

[0098] Figure 6 Another exemplary side sectional view of the propeller fairing shows a mechanism for changing the volume of the propeller fairing (shown here in an expanded state);

[0099] Figure 7 It shows Figure 1 Another schematic diagram of an aircraft drive system, in which a particular embodiment of the propeller fairing adjustment device is shown;

[0100] Figure 8 An exemplary side sectional view of the propeller fairing shows a mechanism for changing the volume of the propeller fairing (shown here in the basic state).

[0101] Figure 9 Another exemplary side sectional view of the propeller fairing shows a mechanism for changing the volume of the propeller fairing (shown here in an expanded state);

[0102] Figure 10 An exemplary front view of a propeller fairing is shown, wherein the propeller fairing has multiple adjustable sheets (shown here overlapping each other) as external panels;

[0103] Figure 11 It shows Figure 10 An exemplary side view of the propeller fairing;

[0104] Figure 12 It shows Figure 10 An exemplary front view of a propeller fairing, wherein the sheet is fanned out; and

[0105] Figure 13 It shows Figure 12 An exemplary side view of the propeller fairing. Detailed Implementation

[0106] The embodiments described below are preferred embodiments of the present invention. In the embodiments, the described components represent individual features of the invention that can be considered independently of each other, and these features also independently improve the invention and are therefore considered as part of the invention individually or in combinations different from those shown. Furthermore, the embodiments can also be supplemented by other features of the invention already described.

[0107] In the accompanying drawings, elements with the same function are respectively assigned the same reference numerals.

[0108] Figure 1 For example, a schematic diagram of aircraft 1 is shown. Aircraft 1 can be, for example, a vertical takeoff and landing (VTOL) aircraft or an eVTOL aircraft. Aircraft 1 is particularly used as a means of transportation for urban air traffic. Aircraft 1 is particularly capable of vertical takeoff and landing.

[0109] The aircraft 1 may have, for example, two wings 2, or wings. The aircraft 1 may have at least one aerodynamic drive 3, which enables the aircraft 1 to operate and, in particular, to move forward. The aerodynamic drive 3 may be referred to, for example, as a propulsion device or drive unit of the aircraft 1. In this embodiment, the aircraft 1 has one aerodynamic drive 3 for each wing 2.

[0110] The aircraft drive unit 3 may have a propeller 4. The propeller 4 may be referred to as an air propeller, for example. The propeller 4 is arranged, for example, on a drive shaft 5 of the aircraft drive unit 3. The propeller 4 can be driven by this drive shaft about a rotation axis 6 of the propeller 4, which may be specifically referred to as a mechanical drive. The rotation axis 6 refers to the axis around which the propeller 4 rotates. The rotation axis 6 may be oriented, for example, parallel to the drive shaft 5.

[0111] The aircraft 1 can be in different flight phases. Here, a flight phase can be, for example, the cruise flight or the cruise flight phase of the aircraft 1.

[0112] exist Figure 1 The image specifically shows an aircraft 1 in cruise flight. During cruise flight, the rotation axis 6 of the propeller 4 is oriented at a predetermined angle relative to the longitudinal axis 7 or longitudinal axis (corresponding to the x-axis) of the aircraft 1, with respect to the horizontal. For example, the rotation axis 6 and the longitudinal axis 7 can be described as substantially parallel. The aircraft drive unit 3 can change its attitude for landing or takeoff. Mechanical adjustment devices can be provided for this purpose. This operation or state of the aircraft 1 is... Figure 2 The image shows hovering flight of aircraft 1. Aircraft 1 can take off and land vertically (corresponding to the z-axis) via hovering flight. Specifically, during hovering flight of aircraft 1, the rotation axis 6 of propeller 4 is oriented at a predetermined angle relative to the longitudinal direction 7 of aircraft 1 with respect to the vertical line. (See image below.) Figure 2 As shown, the axis of rotation 6 can be considered, for example, to be substantially perpendicular to the longitudinal direction 7.

[0113] Back to Figure 1 Furthermore, the aircraft drive unit 3 may have a propeller fairing or fairing 8 as an aerodynamic protection measure. The propeller fairing 8 may be arranged in the front region 10 of the propeller 4 when viewed along the direction 9 of the rotation axis 6 of the aircraft drive unit 3. During the cruise flight of the aircraft 1, the direction 9 of the rotation axis 6 may be the same as the direction 11 of the longitudinal direction 7.

[0114] Therefore, the propeller fairing 8 can be referred to, for example, as the front cover or tip of the propeller 4. Figure 1 As shown, the propeller fairing 8 can be marked in particular at the position of the aircraft drive unit 3 at the foremost position relative to direction 10.

[0115] During hovering flight of aircraft 1 (see...) Figure 2 The direction 9 of the rotation axis 6 can be basically perpendicular to the direction 11 of the longitudinal direction 7.

[0116] Figure 3 A schematic diagram of the aircraft drive unit 3 is shown.

[0117] Because negative characteristics, such as those caused by the propeller 4, may occur, especially during the cruise flight of aircraft 1, the aircraft drive unit 3 may have a propeller fairing adjustment device 12. The propeller fairing adjustment device is an automatic, electromechanical adjustment device. In particular, it can refer to an electromechanical system. For example, each aircraft drive unit 3 may have its own propeller fairing adjustment device 12. Similarly, it is conceivable to provide a central propeller fairing adjustment device, by which all aircraft drive units 3 of aircraft 1 can be controlled and / or regulated. The propeller fairing adjustment device 12 can be particularly referred to as a control unit.

[0118] In particular, the volume of the propeller fairing 8 can be changed by definition along the radial direction 13 relative to the axis of rotation 6 using the propeller fairing adjustment device 12. Therefore, the volume of the propeller fairing 8 can be reduced or increased, for example. In particular, automatic radial enlargement or radial expansion of the propeller fairing 8 can be performed using the propeller fairing adjustment device 12. The volume of the propeller fairing 8 can be changed, adapted, or adjusted, for example, according to the attitude of the aircraft drive unit 3 and / or the flight phase of the aircraft 1.

[0119] For example, the volume of the propeller fairing 8 can be adjusted from its basic state using the propeller fairing adjustment device 12 (which can be done in...). Figure 3 (as seen in) changes to at least one extended state (this can be seen in) Figure 4 (See [reference]). The volume in the expanded state compared to the basic state (see [reference]). Figure 4 In particular, it is expanded or enlarged. As already mentioned, Figure 4 This diagram illustrates one possible expansion state of the propeller fairing 8 among different expansion states. The volume of the propeller fairing 8 can be modified in such a way that the front portion of the propeller leading surface 14 of the propeller 4 is at least regionally covered by the volume-modified propeller fairing 8. Here, the propeller 8 is covered, in particular (viewed with reference to the direction 9 of the axis of rotation 6), forward. In other words, the front region 10 of the propeller 4 can be at least regionally covered. In particular, the area of ​​the propeller 8 that generates negative thrust or reduces efficiency due to downward drive can be covered by the volume 8 modified in the expansion state. This allows for more efficient cruise flight, and thus, in particular, an increased range for the aircraft 1.

[0120] Furthermore, the front surface 14 of the propeller can be the entire surface of the propeller 4 with reference to the front region 10 of the propeller 4.

[0121] The propeller fairing 8, in its expanded state, can at least regionally, and especially completely, cover or obscure the propeller front surface 14 on the side 15 facing the propeller 4. At least one partial surface 16 of the propeller front surface 14, located radially inward relative to the axis of rotation 6 of the propeller 4 and extending radially outward from the axis of rotation 6, can be covered, in particular, by the propeller fairing 8 in its radially expanded expanded state. The inner partial surface 16 extends radially 13 from the axis of rotation 6. Compared to the basic state (see...), Figure 3 The internal local surface 16 is covered, especially along a larger radial range, in the expanded state. Figure 4 It is also known that, compared to the basic state, the rear end 17 of the propeller fairing 8, facing the propeller 4, expands radially in the expanded state. The propeller fairing expands or enlarges further with reference to radial direction 13. The rear end 17 is located at the opposite end of the propeller fairing 8 with reference to direction 9.

[0122] The propeller 4 has, for example, at least two propeller blades 19, 18. Optionally, the propeller 4 may have multiple propeller blades 18, 19. The propeller blades 18, 19 are connected to or mechanically coupled to the drive shaft 5 at a connection point 20 of the propeller 4. The connection point 20 may be, in particular, the center of the propeller 4. The connection point 20 is, in particular, a propeller hub or a rotor hub. The axis of rotation 6 may extend centrally through the connection point 20, for example, so that the connection point 20 can also rotate symmetrically about the axis of rotation 6. The connection point 20 may be connected to the drive shaft 5, for example, along the axis of rotation 6, so that the propeller 4, in particular the propeller blades 18, 19, rotate according to the rotational speed.

[0123] At least two propeller blades 18, 19, corresponding surface regions 21, 22, may, for example, be covered at least regionally on the front side relative to the front region 10 by a propeller fairing 8 whose volume is changed by the propeller fairing adjustment device 12. The two surface regions 21, 22, for example, form an internal partial surface 16.

[0124] The corresponding surface regions 21, 22 extend particularly toward the connection position 20 and away from the corresponding radial end regions 23, 24 of at least two propeller blades 18, 19. The corresponding surface regions 21, 22 can thus be located near the center of the connection position 20 and, in particular, near the center of the propeller 4.

[0125] The corresponding surface regions 21 and 22 may correspond to at least 20%, especially 30%, and especially 40% of the corresponding propeller front surface 14 of at least three propeller blades 18 and 19. This can, for example, cover the propeller region inside the propeller 4. The corresponding surface regions 21 and 22 may, for example, correspond to one-third, especially one-quarter, of the front surface of the corresponding propeller blades 18 and 19.

[0126] In particular, one-third, and especially one-quarter, of the front surface 14 of the propeller can be covered by the propeller fairing 8, whose volume changes in the expanded state.

[0127] The propeller fairing 8 may, for example, be at least partially, and especially entirely, made of an anisotropic elastic material. The propeller fairing 8 may, for example, have at least one reinforcing element 26 on the outer side 27 along the circumferential direction 25 (see...). Figure 8 At least one reinforcing element 26, especially a stabilizing element, is provided to improve the stability of the propeller fairing 8, particularly during cruise flight. The propeller fairing 8 may have multiple reinforcing elements 26.

[0128] The propeller fairing 8 may, for example, have a housing 28 (see...) Figure 1 The housing 28 can be referred to, for example, as an outer casing or external housing. The housing 28 can be designed in a parabolic shape. Therefore, the housing 28, and especially the propeller fairing 8, has a parabolic shape. The housing 28 can expand radially and rotationally symmetrically about the axis of rotation 6, thereby changing the volume of the propeller fairing 8.

[0129] Figure 5 In particular, a feasible embodiment or mechanism for changing the volume of the propeller fairing 8 is shown. The propeller fairing adjustment device 12 can be arranged, for example, in the internal region 29 or cavity of the propeller fairing 8. The movable adjustment element 30 of the propeller fairing adjustment device can be arranged in the front side 31 away from the propeller 4 (with reference to the direction 9 of the axis of rotation 6). Figure 5 In particular, the basic state of the propeller fairing 8 and, especially, the basic state of the movable adjustment element 30 are shown. Figure 6 At least one expanded state of the propeller fairing 8 is shown. The basic state is again visualized here by dashed line 32. Here, a movable adjustment element 30 moves from the front 31 toward the propeller 4 via the propeller fairing adjustment device 12 to change the volume within the internal region 29. For this purpose, the movable adjustment element 30 can, for example, move toward the direction of the propeller 4 (opposite to direction 9) via the main shaft 33. The adjustment element 30 moves particularly toward the mating element 34. This movement within the propeller fairing 8 enables the expansion or change of volume.

[0130] exist Figure 7 Another feasibility for changing the volume is shown. The propeller fairing adjustment device 12 can, for example, be arranged outside the propeller fairing 8. This can, for example, be achieved in a region of the propeller 4 that is far away from the direction 9. However, in this context... Figure 6 The design scheme differs in that the main shaft 33 or threaded main shaft is arranged outside the propeller fairing 8, especially completely outside the propeller fairing 8. The propeller fairing adjustment device 12 can therefore include, for example, a motor 35. The motor 35 can, for example, include a housing 36, a stator 37, a rotor 38, and a hollow shaft 39. Bearings 40 can also be provided. An adjustment actuator 41 can be provided to adjust the movable adjustment element 30. This adjustment actuator can be operated by means of the motor 35. The adjustment actuator 41 can be arranged inside the propeller fairing 8. For this purpose, a cable guide device can be provided, for example. The motor 35 particularly includes a cooling air guide device 42.

[0131] exist Figure 7 The propeller fairing 8 shown can be a torsion-resistant fairing in particular.

[0132] exist Figure 8 Another feasibility for changing volume is illustrated. The propeller fairing adjustment device 12 can here have a pneumatic or hydraulic adjustment unit 43. This adjustment unit 43 can be arranged, in particular, in the internal region 29 of the propeller fairing 8. At least one inflatable element 44 arranged in the internal region 29 can be controlled by means of the pneumatic adjustment unit 43, which can be controlled and / or regulated by the propeller fairing adjustment device 12. Here, the inflatable element can be inflated to change volume, especially expand volume. Figure 8 In particular, the basic state of the propeller fairing 8 is shown.

[0133] Figure 9 The expansion state is also shown. Figure 9 In this configuration, at least one inflatable element 44, such as an inflatable ring, is inflated, particularly filled with air or gas, thereby expanding the volume of the propeller fairing 8. The inflatable element 44 can be controlled, in particular, by means of a pneumatic adjustment unit 43. Here, the inflatable element can be inflated or deflated again according to the volume requirements of the propeller fairing 8.

[0134] In the next Figures 10 to 13 Another feasibility for changing the volume of the propeller fairing 8 is shown in the figure.

[0135] Figure 10 Here is, for example, a front view of the propeller fairing 8 as seen from the front region 10.

[0136] The propeller fairing 8 may, for example, have multiple sheets 46 that can be adjusted by the propeller fairing adjustment device 12 as an outer panel 45. Figure 10 The original state 32 of the propeller fairing 8 is shown here again. In the basic state or original state 32, the sheets 46 are arranged overlapping each other along the circumferential direction 25 or the rotational direction around the axis of rotation 6. For this purpose, for example in Figure 11 The image shows a side view.

[0137] To change the volume 8, the sheet 46 can be adjusted or altered, causing the sheet 46 to open in a fan shape, in particular. This is... Figure 12 As shown in the diagram. Sheet 46 is manipulated here, particularly by means of the propeller fairing adjustment device 12, so that the sheet opens in a fan shape. This causes the volume to expand radially. This can be achieved... Figure 12 This can be seen in the comparison with the basic state 32. Multiple sheets 46 are manipulated or adjusted such that the multiple sheets 46 have a preset distance 47 between them. This, for example, can be achieved from... Figure 13 It can be seen that the volume of the propeller fairing 8, especially the elastic propeller fairing 8, can therefore be expanded or increased by the spaced-apart sheets 46.

[0138] In one embodiment of the invention, the volume of the propeller fairing 8 can be automatically changed radially 13 relative to the axis of rotation 6 by the propeller fairing adjustment device 12 according to the attitude of the aircraft drive unit 3 and / or the flight stage of the aircraft 1. Therefore, the volume of the propeller can be adjusted on the system side by an electromechanical system.

[0139] Furthermore, for example, the volume of the propeller fairing 8 can be changed from the basic state 32 to at least an expanded state by means of the propeller fairing adjustment device 12, such that the propeller leading surface 14 of the propeller 4 is at least regionally covered forward by the volume-changed propeller fairing 8 to a greater extent than in the basic state 32. This can also be accomplished by an automated system, especially a control and / or regulation device.

[0140] Furthermore, the attitude of the aircraft drive unit 3 in cruise flight attitude (see...) Figure 1 ) and hovering flight attitude (see Figure 2 When the volume of the propeller fairing 8 changes between these values, it can, for example, change automatically. The propeller fairing adjustment device 12 can, for example, have an electronic analysis unit (see [link to relevant documentation]). Figure 3The volume of the propeller fairing 8 can be set to an expanded state during cruise flight and a basic state during hovering flight. Depending on the corresponding attitude of the aircraft drive and / or the operating state of the aircraft 1, the time point and / or duration for changing the volume of the propeller fairing 8 and / or the volumetric dimension by which the volume of the propeller fairing 8 changes can be determined. This can be determined by means of an electronic analysis unit or calculation unit 48 and transmitted to the corresponding unit.

[0141] The propeller fairing 8 may, for example, be made of a shape memory alloy, through which the shape of the propeller fairing 8 can be changed. For example, the control or multiple control of changing the volume of the propeller fairing 8 can be achieved by means of piezoelectric control or control controlled by centrifugal force.

[0142] List of reference numerals

[0143] 1. Aircraft

[0144] 2. Wings

[0145] 3. Aircraft drive unit

[0146] 4 propellers

[0147] 5 drive shafts

[0148] 6. Rotation axis

[0149] 7. Vertical

[0150] 8. Propeller fairing

[0151] 9. Direction of the axis of rotation

[0152] 10. Front area of ​​the propeller

[0153] 11. The longitudinal direction of the aircraft

[0154] 12. Propeller fairing adjustment device

[0155] 13 Radial

[0156] 14 Propeller front surface

[0157] 15. The side of the propeller fairing facing the propeller.

[0158] 16. A partial surface inside the front surface of the propeller

[0159] 17. Rear end of the propeller fairing

[0160] 18 and 19 propeller blades

[0161] 20 Connection Location

[0162] Areas 21 and 22

[0163] 23, 24 Radial end regions

[0164] 25 Zhou Xiang

[0165] 26 Reinforcing Components

[0166] 27 Outer side

[0167] 28. Shell

[0168] 29 Internal Area

[0169] 30 Adjustment element

[0170] 31. Front side of the propeller fairing

[0171] 32 Basic State

[0172] 33 Spindle

[0173] 34. Mating components

[0174] 35 Electric Motor

[0175] 36. Electric motor casing

[0176] 37. Stator of an electric motor

[0177] 38. The rotor of an electric motor

[0178] 39 Hollow Shaft

[0179] 40 bearing

[0180] 41. Adjusting actuator

[0181] 42 Cooling air guiding device

[0182] 43. Pneumatic control unit

[0183] 44. Inflatable components

[0184] 45 External Panels

[0185] 46+ sheets

[0186] 47. Distance between sheets

[0187] 48 Electron Analysis Unit

Claims

1. An aviation drive unit (3) for an aircraft (1), the aviation drive unit comprising: - A propeller (4), which is arranged on the drive shaft (5) of the aircraft drive unit (3) and can be driven by the drive shaft (5) about the rotation axis (6) of the propeller (4). - A propeller fairing (8), which is arranged in the front region (10) of the propeller (4) as viewed in the direction (9) along the rotation axis (6) of the aircraft drive unit (3). - A propeller fairing adjustment device (12) for changing the volume of the propeller fairing (8) radially (13) relative to the axis of rotation (6) by a defined method. Its features are, The propeller fairing adjustment device (12) can change the volume of the propeller fairing (8) from its basic state to at least one expanded state, such that the propeller front surface (14) of the propeller (4) is covered at least regionally by the volume-changed propeller fairing (8) to a greater extent than in the basic state.

2. The aircraft drive device (3) according to claim 1, Its features are, The propeller fairing (8) covers at least regionally the front surface (14) of the propeller (4) on one side (15) facing the propeller (4).

3. The aircraft drive device (3) according to claim 2, Its features are, At least one local surface (16) of the front surface (14) of the propeller, which is located radially inward relative to the axis of rotation (6) of the propeller (4) and extends radially outward from the axis of rotation (6), is covered by the propeller fairing (8) in its radially expanded state over a greater extent than in its basic state.

4. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, Compared to the basic state, the rear end (17) of the propeller fairing (8) towards the propeller (4) expands radially in the expanded state.

5. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, The propeller (4) has at least two propeller blades (18, 19), which are connected to the drive shaft (5) at the connection position (20) of the propeller (4), wherein the corresponding surface regions (21, 22) of the at least two propeller blades (18, 19) extending toward the connection position (20) and away from the corresponding radial end regions (23, 24) of the at least two propeller blades (18, 19) are at least regionally covered on the front side by a propeller fairing (8) whose volume is changed by the propeller fairing adjustment device (12).

6. The aircraft drive device (3) according to claim 5, Its features are, The corresponding surface regions (21, 22) of the at least two propeller blades (18, 19) correspond to at least 20% of the corresponding propeller front surface (14) of the at least two propeller blades (18, 19).

7. The aircraft drive device (3) according to claim 6, Its features are, The corresponding surface regions (21, 22) of the at least two propeller blades (18, 19) correspond to 30% of the corresponding propeller front surface (14) of the at least two propeller blades (18, 19).

8. The aircraft drive device (3) according to claim 6, Its features are, The corresponding surface regions (21, 22) of the at least two propeller blades (18, 19) correspond to 40% of the corresponding propeller front surface (14) of the at least two propeller blades (18, 19).

9. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, The propeller fairing (8) is at least partially made of an anisotropic elastic material.

10. The aircraft drive device (3) according to claim 9, characterized in that, The propeller fairing (8) is made entirely of anisotropic elastic material.

11. The aircraft drive device (3) according to claim 9, characterized in that, The propeller fairing (8) has at least one reinforcing element (26) on the outer side (27) along the circumferential direction (25).

12. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, The casing (28) of the propeller fairing (8) is designed as a parabolic surface.

13. The aircraft drive device (3) according to any one of claims 1 to 3, characterized in that, The shell (28) of the propeller fairing (8) can expand radially in a rotationally symmetrical manner about the axis of rotation (6).

14. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, The propeller fairing (8) has a plurality of sheets (46) as an outer panel (45) that can be adjusted by the propeller fairing adjustment device (12). The plurality of sheets (46) are arranged overlapping each other along the circumferential direction (25) around the axis of rotation (6) in the basic state of the volume of the propeller fairing (8). In order to change the volume of the propeller fairing (8), the plurality of sheets (46) are adjusted by the propeller fairing adjustment device (12) such that the plurality of sheets (46) have a predetermined distance (47) from each other.

15. The aircraft drive unit (3) according to any one of claims 1 to 3, Its features are, The propeller fairing adjustment device (12) is arranged in the internal region (29) of the propeller fairing (8), wherein the movable adjustment element (30) of the propeller fairing adjustment device (12) is arranged on the front side (31) of the propeller fairing (8) away from the propeller (4), wherein the movable adjustment element (30) is configured to move in the internal region (29) from the side (31) away from the propeller (4) toward the propeller (4) by means of the propeller fairing adjustment device (12) to change the volume of the propeller fairing (8).

16. The aircraft drive device (3) according to any one of claims 1 to 3, Its features are, The propeller fairing adjustment device (12) has a pneumatic adjustment unit (43), wherein at least one inflatable element (44) arranged in the internal region (29) of the propeller fairing (8) can be controlled by the pneumatic adjustment unit (43) to change the volume of the propeller fairing (8).

17. An aircraft (1) having at least one aerodynamic drive (3) according to any one of claims 1 to 16. Its features are, During hovering flight of the aircraft (1), the rotation axis (6) of the propeller (4) is oriented at a predetermined angle relative to the longitudinal direction (7) of the aircraft (1) with respect to the vertical line, and during cruise flight of the aircraft (1), the rotation axis (6) of the propeller (4) is oriented at a predetermined angle relative to the longitudinal direction (7) of the aircraft (1) with respect to the horizontal line.

18. A method for operating an aircraft drive unit (3) for an aircraft (1), wherein, The propeller (4) of the aircraft drive unit (3) arranged on the drive shaft (5) of the aircraft drive unit (3) is driven by the drive shaft (5) about the rotation axis (6) of the propeller (4). Its features are, The volume of the propeller fairing (8) arranged in the front region (10) of the propeller (4) viewed along the direction (9) of the rotation axis (6) of the aircraft drive unit (3) is changed radially (13) relative to the rotation axis (6) by the propeller fairing adjustment device (12) according to the attitude of the aircraft drive unit (3), wherein the volume of the propeller fairing (8) is changed from a basic state to at least one expanded state by the propeller fairing adjustment device (12) such that the propeller front surface (14) of the propeller (4) is at least regionally covered forward by the volume-changed propeller fairing (8) to a greater extent than in the basic state.

19. The method according to claim 18, Its features are, The volume of the propeller fairing (8) automatically changes as the aircraft drive unit (3) changes its attitude between cruise flight attitude and hover flight attitude.

20. The method according to claim 19, characterized in that, The volume of the propeller fairing (8) is set to an expanded state in cruise flight attitude and to a basic state in hover flight attitude.

21. The method according to claim 19, characterized in that, The timing and / or duration for changing the volume of the propeller fairing (8) and / or the volume size to which the volume of the propeller fairing (8) is changed are determined based on the attitude of the aircraft drive unit (3) and / or the operating state of the aircraft (1).

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