System and method for motor cooling in VTOL aircraft

Abstract

A VTOL aircraft includes a plurality of lift propellers configured to be rotated by lift motors to provide vertical thrust during takeoff, landing, and hover operations. The lift propeller is configured to generate a flow of cooling air to cool the lift motor during use. During cruise operation, the lift propellers may be stowed in a rest position when the VTOL aircraft is in forward motion. Thus, when the flow of cooling air is not needed, the flow of cooling air may be reduced or eliminated.

Description

[0001] This application is a divisional application of the international application entering the Chinese national phase with the application date of November 14, 2023, the international application number PCT / US2023 / 079676, the national application number 202380084476.5, and the name “System and method for motor cooling in VTOL aircraft”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This disclosure claims priority to and the benefit of U.S. patent application Ser. No. 18 / 163,372, filed on February 2, 2023, entitled “SYSTEMS AND METHODS FOR LIFTER MOTOR COOLING IN EVTOL AIRCRAFT,” (Attorney Docket No. 16163.0005-01000), which in turn claims priority to and the benefit of U.S. patent application Ser. No. 18 / 055,268, filed on November 14, 2022, entitled “SYSTEMS AND METHODS FOR LIFTER MOTOR COOLING IN EVTOL AIRCRAFT,” (Attorney Docket No. 16163.0005-00000), which in turn claims priority to and the benefit of U.S. patent application Ser. No. 18 / 055,268, filed on October 7, 2022, entitled “Systems and Methods for Improved Propulsion Systems for eVTOL Aircraft,” (Attorney Docket No. 16163.0005-00000), which in turn claims priority to The present invention claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 378,680 (Attorney Docket No. 16163.6002-00000) for "Aircraft." The entire contents of the aforementioned patent are incorporated herein by reference in their entirety for all purposes. Technical Field

[0004] The present disclosure generally relates to the field of powered aerial vehicles. More specifically, but not limited to, the present disclosure relates to innovations for eVTOL aircraft using electric propulsion systems. Certain aspects of the present disclosure generally relate to cooling paths for motors (e.g., lift motors for powered aerial vehicles). Other aspects of the present disclosure generally relate to improvements in motors that can be used in other types of aircraft but offer specific advantages in aerial vehicles. Summary of the Invention

[0005] Some embodiments of the present disclosure provide an apparatus for a vertical take-off and landing (VTOL) aircraft. The apparatus may include a propeller, a support structure for the VTOL aircraft, an electric engine mounted to the support structure and configured to rotate the propeller, the electric engine being located within a housing, a first heat transfer element thermally coupled to the electric engine, wherein at least a portion of the first heat transfer element is located outside the housing, an air inlet located on an upper side of the support structure, wherein the air inlet is configured to receive downwash from the propeller during a lift phase, a first cooling path configured to direct a first portion of the downwash from the air inlet to the first heat transfer element, and a first air outlet configured to discharge the first portion of the downwash from the first heat transfer element.

[0006] Some embodiments of the present disclosure provide an apparatus for a VTOL aircraft. The apparatus may include a propeller, a support structure for the VTOL aircraft, an electric engine mounted to the support structure and configured to rotate the propeller, an air inlet located on an upper side of the support structure, wherein the air inlet is configured to receive downwash from the propeller during a lift phase, a first cooling path configured to direct a first portion of the downwash from the air inlet to a first portion of the electric engine, and a second cooling path configured to direct a second portion of the downwash from the air inlet to a second portion of the electric engine.

[0007] Some embodiments of the present disclosure provide a lift device for a VTOL aircraft. The lift device may include: a lift propeller; a propeller controller electrically coupled to the lift propeller, the propeller controller being located within a controller housing; a heat exchanger including fins located outside the controller housing, the heat exchanger fins being thermally coupled to the propeller controller via an oil flow path; a boom; a fairing; an air inlet located at a top side of the fairing, the air inlet being configured to receive downwash from the lift propeller during a lift phase; a cooling path configured to direct the downwash to cool the heat exchanger fins; and an air outlet configured to discharge the downwash from the heat exchanger fins. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram illustrating an exemplary VTOL aircraft consistent with the disclosed embodiments.

[0009] Figure 2 is a schematic diagram illustrating an exemplary VTOL aircraft consistent with embodiments of the present disclosure.

[0010] Figure 3 is a schematic diagram illustrating an exemplary VTOL aircraft consistent with embodiments of the present disclosure.

[0011] Figures 4A-4C is a schematic diagram illustrating an exemplary lift propeller and motor assembly for a VTOL aircraft consistent with embodiments of the present disclosure.

[0012] Figure 5A-Figure 5N is a schematic diagram illustrating example oil and air flow paths within a motor assembly and surrounding area of ​​a VTOL aircraft consistent with embodiments of the present disclosure.

[0013] Figures 6A-6E is a schematic diagram illustrating an example air flow path arrangement in a portion of a VTOL aircraft consistent with embodiments of the present disclosure.

[0014] Figure 7A-7B is a schematic diagram illustrating an example door arrangement in a portion of a VTOL aircraft consistent with embodiments of the present disclosure.

[0015] Figure 8 is a schematic diagram illustrating auxiliary features in a portion of a VTOL aircraft consistent with an embodiment of the present disclosure.

[0016] Figure 9A-9B is a schematic diagram illustrating auxiliary features in a portion of a VTOL aircraft consistent with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] The present disclosure relates to components of electric vertical take-off and landing (eVTOL) aircraft primarily for unconventional aircraft. For example, the eVTOL aircraft of the present disclosure may be intended for frequent (e.g., more than 50 flights per weekday), short-duration flights (e.g., less than 100 miles per flight) over, into and out of densely populated areas. The aircraft may be intended to carry 4 to 6 passengers or commuters who desire to obtain a low-noise and low-vibration experience. Therefore, it may be necessary for their components to be configured and designed to withstand frequent use without wear and tear, to generate less heat and vibration, and to require the aircraft to include a mechanism for effectively controlling and managing the heat or vibration generated by the components. In addition, it may be expected that several of these aircraft will operate close to each other over crowded metropolitan areas. Therefore, it may be necessary for their components to be configured and designed to generate low levels of noise inside and outside the aircraft, and to be configured and designed to have various safety and backup mechanisms. For example, for safety reasons, it may be necessary for the aircraft to be propelled by a distributed propulsion system to avoid the risk of a single point failure, and to require them to be able to perform conventional takeoff and landing on a runway. Furthermore, when transporting approximately 4 to 6 passengers or commuters with luggage, the aircraft may need to be able to safely take off and land vertically from and into relatively confined spaces (e.g., vertiports, parking areas, or driveways) compared to traditional airport runways. These operational requirements may impose design constraints on aircraft size, weight, and operational efficiency (e.g., drag, energy use), which may affect the design and configuration of aircraft components.

[0018] The disclosed embodiments provide for new and improved configurations of aircraft components not observed in conventional aircraft, and / or design criteria for components that differ from those of conventional aircraft. Such alternative configurations and design criteria, combined with addressing the shortcomings and challenges of conventional components, result in the various configurations and designs of eVTOL aircraft components disclosed herein.

[0019] In some embodiments, the eVTOL aircraft of the present disclosure can be designed to be capable of both vertical takeoff and landing and conventional takeoff and landing, with a distributed electric propulsion system enabling vertical flight, forward flight, and transition. Thrust can be generated by supplying high-voltage electric power to the distributed electric propulsion system's electric engines, which each convert the high-voltage electric power into mechanical shaft power to rotate the propellers. Embodiments disclosed herein may involve optimizing the energy density of the electric propulsion system. Embodiments may include electric engines connected to an onboard electric power source, which may include a device capable of storing energy, such as a battery or capacitor, or may include one or more systems for utilizing or generating electricity, such as a fuel-powered generator or a solar panel array. Some disclosed embodiments provide for reduced weight and space requirements for components in the aircraft, thereby improving aircraft efficiency and performance. Given the increasing concern for safety in passenger transportation, the disclosed embodiments implement new and improved safety protocols and system redundancy in the event of a failure to minimize any single point of failure in the aircraft's propulsion system. Some disclosed embodiments also provide new and improved methods for meeting aviation and transportation laws and regulations. For example, the United States Federal Aviation Administration enforces federal regulations that require safety features, such as fire barriers, near engines that use oil or other flammable materials in excess of a threshold amount.

[0020] In a preferred embodiment, the distributed electric propulsion system may include twelve electric engines mounted on booms located at the front and rear of the aircraft's main wings. The front electric engines may be tiltable during flight between a horizontal orientation (e.g., to generate forward thrust) and a vertical orientation (e.g., to generate vertical lift). The front electric engines may be of either a clockwise or counterclockwise type with respect to the direction of propeller rotation. The tail electric engines may be fixed in a vertical orientation (e.g., to generate vertical lift). These tail electric engines may also be of either a clockwise or counterclockwise type with respect to the direction of propeller rotation. In some embodiments, the aircraft may be equipped with various combinations of front and tail electric engines. For example, the aircraft may be equipped with six front and six tail electric engines, four front and four tail electric engines, or any other combination of front and tail engines, including embodiments in which the number of front and tail electric engines is unequal. In some embodiments, an aircraft may be provided with four front propellers and four tail propellers, wherein at least four of the propellers comprise tiltable propellers.

[0021] In a preferred embodiment, for vertical take-off and landing (VTOL) missions, the front electric engine and the tail electric engine can provide vertical thrust during take-off and landing. During the flight phase when the aircraft is in forward flight mode, the front electric engine can provide horizontal thrust, while the propeller of the tail electric engine can be stowed in a fixed position to minimize drag. The tail electric engine can be actively stowed using position monitoring. The transition from vertical flight to horizontal flight and vice versa can be achieved via a tilt propeller subsystem. The tilt propeller subsystem can redirect thrust between a primary vertical direction during vertical flight mode and a primary horizontal direction during forward flight mode. The variable pitch mechanism can change the collective angle of the propeller hub assembly blades of the front electric engine for operation during the hover phase, transition phase, and cruise phase.

[0022] In some embodiments, the front electric engine can provide horizontal thrust for wing-borne takeoff, cruise, and landing during conventional takeoff and landing (CTOL) missions. In some embodiments, the tail electric engine may not be used to generate thrust during CTOL missions and the tail rotor may be stowed in place.

[0023] In some embodiments, the electric engine can be housed or connected to the boom of the aircraft and include a motor, an inverter, and a gearbox. In some embodiments, the motor, inverter, and gearbox can be coupled so that they share a central axis. In some embodiments, torque from the motor can be sent to the gearbox away from the propeller of the propulsion system. In some embodiments, the gearbox can provide gear reduction and then transmit the torque back to the propeller via a main shaft through bearings located inside the motor. In some embodiments, the inverter can be mounted at the rear of the gearbox so that the main shaft does not move through the inverter when outputting torque to the propeller. In some embodiments, the motor, gearbox, and inverter can be coupled so that a coolant, such as oil, can be used to maintain the motor, inverter, and / or gearbox while sharing a common heat exchanger. In some embodiments, the amount of oil used to lubricate and cool the electric engine can vary, including amounts of less than one quart, two quarts, three quarts, or any other measured amount of oil.

[0024] In some embodiments, the tilt-propeller system may include a linear or rotary actuator to change the orientation of the propulsion system during operation. In some embodiments, the pitch of the propulsion system can be changed according to the orientation of the propulsion system. In some embodiments, the rotary actuator may include a motor, an inverter, and a gearbox. In some embodiments, the gearbox may include various types of gears that engage to provide a gear reduction capable of directional propulsion system. In some embodiments, the tilt-propeller system may include a redundant configuration such that there are multiple motors, inverters, and gearboxes and the gears are used for interface connection. In some embodiments, a configuration utilizing multiple motors, gearboxes, and inverters can allow a failed portion of the redundant configuration to be driven by the motors, inverters, and gearboxes of another portion of the configuration. In some embodiments, the gearbox configuration can also allow the tilt-propeller system to maintain the orientation of the propulsion system with the help of additional power provided by the system or without additional power provided by the system.

[0025] In some embodiments, an electric propulsion system as described herein can generate thrust by supplying high voltage (HV) electric power to an electric engine, which in turn converts the HV electric power into mechanical shaft power for rotating a propeller. As described above, an aircraft as described herein can have multiple electric engines mounted on the front and tail of the wing using booms. The amount of thrust generated by each electric engine can be controlled by torque commands sent to each electric engine by a flight control system (FCS) via a digital communication interface. An embodiment may include a front electric engine and may be capable of changing its orientation or tilt. Additional embodiments include a front engine that can be of a clockwise (CW) type or a counterclockwise (CCW) type. The front electric engine propulsion subsystem can consist of a multi-blade controllable pitch propeller and a variable pitch subsystem.

[0026] In some embodiments, the aircraft may include a tail engine or lifter that may be of the clockwise (CW) type or the counterclockwise (CCW) type. Additional embodiments may include a tail electric engine that utilizes a multi-bladed fixed pitch propeller.

[0027] As described herein, the orientation and use of the electric propulsion system can change throughout the operation of the aircraft. In some embodiments, during vertical takeoff and landing, the front propulsion system and the tail propulsion system can provide vertical thrust during takeoff and landing. During the flight phase when the aircraft is in forward flight mode, the front propulsion system can provide horizontal thrust, while the propellers of the tail propulsion system can be stowed in a fixed position to minimize drag. The tail electric propulsion system can be actively stowed using position monitoring. Some embodiments may include a transition from vertical to horizontal flight, and vice versa. In some embodiments, the transition can be achieved via a tilt propeller system (TPS). The TPS redirects thrust between a primarily vertical direction during vertical flight mode and a primarily horizontal direction during forward flight mode. Additional embodiments may include a variable pitch mechanism that can change the total blade angle of the front propulsion system propeller hub assembly for operation during the hover phase, cruise phase, and transition phase. Some embodiments may include a conventional takeoff and landing (CTOL) configuration, such that the tiltrotor provides horizontal thrust for wing-borne takeoff, cruise, and landing. The tail electric engine is not used to generate thrust during the CTOL mission and the tail propeller is retracted into position.

[0028] In some embodiments, the electric engine described herein may include design features to mitigate and prevent uncontained fires, such as utilizing a non-hazardous amount of flammable fluid contained in both the tilt and lift engines, lacking a nominal ignition source within the electric engine, an engine over-temperature operating limit that is at least 50°C below the auto-ignition temperature of the flammable fluid, over-temperature detection and protection, over-voltage detection and protection, and over-current detection and protection. In some embodiments, the design features of the electric engine may deem it to be non-designated fireproof. In some embodiments, the flammable fluid may include oil, and the non-hazardous amount may be less than one, two, three, four, five, or ten quarts, as determined based on factors such as the aircraft's size, number of propellers, or payload.

[0029] As disclosed herein, an electric power engine may include an inverter and a motor; or various configurations of inverters, gearboxes, and motors, such as the representative configurations described herein. For example, an electric power engine may include an electric motor, a gearbox, and an inverter, all of which share the same central axis. Additionally, the central axis may be configured along the axis of an output shaft leading to a propeller of an aircraft. In this exemplary configuration, the motor, gearbox, and inverter will all share the output shaft as the central axis and will be oriented circularly around the output shaft. Additional embodiments may include a motor, gearbox, and inverter mounted together in sequence, or a configuration in which some components (such as the motor and gearbox) are mounted together and other components (such as the inverter) are located elsewhere but a wiring system is used to connect the electric power engine.

[0030] As described above, an electric engine for an aircraft as described herein may include some or all of a motor, an inverter, and a gearbox. Various configurations may include an inverter and a motor such that the output shaft of the motor directly provides speed and torque to the propeller shaft. Additional embodiments of the electric engine may include a motor, an inverter, and a gearbox, wherein the output of the motor may pass through a gearbox connected to the output shaft of the propeller; a motor, an inverter, and a gearbox, wherein the output from the motor passes through a gearbox away from the propeller, wherein the output shaft of the propeller passes through the gearbox and the motor back to the propeller. As described herein, the electric engine may contemplate any combination or orientation of some or all of the motor, inverter, and gearbox. In addition, each configuration or orientation of the electric engine as disclosed herein may include cooling via air cooling, coolant liquid, or a mixture of the two.

[0031] For example, an electric engine configuration may include a motor and an inverter, wherein the motor is located between the propeller of the aircraft and the inverter. In addition, the motor may include a gearbox. Furthermore, the inverter may share the same central axis as the motor, wherein the inverter may be located in a housing that cantilevers out from the rear of the motor and may be air-cooled. It will be appreciated that this inverter orientation may not be the optimal configuration in terms of the housing required to achieve this cantilevered orientation. Additionally, the motor in this configuration utilizing air cooling may include potting material, and air fins to assist in motor cooling may result in an even greater increase in system mass.

[0032] Some embodiments may include electric engines in which the inverter module may be mounted external to the motor housing. Additional embodiments may include electric engines in which the inverter may be mounted on top of the electric motor so that the inverter's air cooling fins are below the propeller. Further embodiments may include: mounting the inverter to the rear of the motor with the air cooling fins facing radially outward; mounting the inverter to the front of the motor with the air cooling fins facing radially outward; mounting the inverter to the motor with the inverter cooled by a liquid, such as oil; or any other location of the inverter relative to the motor.

[0033] Embodiments of an electric motor may include a stator housing, a wound stator assembly, a rotor, various bearings, and any additional components that facilitate transferring the speed and torque generated by the motor to the propeller.

[0034] It should be understood that the power engine can generate heat during operation and may include a thermal management system to ensure that components of the power engine do not fail during operation. In some embodiments, a coolant can be used and circulated in various components of the engine (such as the inverter, gearbox, or motor), through some components or through all components of the engine to help manage the heat present in the engine. Additional embodiments may include using air cooling methods to cool the power engine, or using a mixture of coolant and air to manage the heat generated by the power engine during operation. In some embodiments, the coolant used can also be the same liquid used as a lubricant throughout the inverter, gearbox, or motor. For example, liquid or air can be used to cool the inverter, gearbox, and motor, or a mixture of air and liquid cooling can be used, such as using air cooling to cool the motor and using liquid cooling in the inverter and gearbox, or any other combination of air and liquid cooling on the inverter, gearbox, and motor, or even a subset of these components.

[0035] In some embodiments, oil can be used as a lubricant throughout the electric engine and also as a coolant fluid to help manage the heat generated by the engine during operation. Further to this example, varying amounts of oil can be used as both the lubricant and coolant fluid in the electric engine, with or without air cooling assistance, such as less than one quart, less than two quarts, or any other amount required to lubricate and cool the electric engine. As disclosed herein, electric engines can have different primary functions, such as being used only for lift and landing and therefore only in a single orientation, or being used during all phases of flight, such as lift, landing, and flight. An engine used in all phases of flight may experience various orientations throughout flight and may include more lubricant and coolant than an engine used in only one orientation. Therefore, all engines on an aircraft may not contain the same amount of lubricant and coolant. For example, a lift and landing engine may require less than one quart of oil, while an engine operating in all phases of flight may require more than one quart of oil. It should be understood that the example embodiments described herein are representative and do not prescribe limits on the amounts of lubricant and coolant that can be used in an electric engine.

[0036] It should be understood that by using oil to not only lubricate but also cool the electric engine, rather than using another coolant, this will add additional oil to the system, but this additional oil will eliminate traditional components that could be used to cool such an electric engine. For example, if the electric engine were cooled by another liquid, such as ethylene glycol, the engine would likely include separate heat exchangers for both the lubricant fluid and the coolant fluid. Thus, in embodiments using a single fluid (e.g., oil) for both lubrication and cooling, there would be an increase in oil, but only one heat exchanger would be required, so since fewer heat exchangers are used and additional components may not be required, the mass of the entire system can be reduced, and a more attractive drag profile may be achieved. Furthermore, using a single substance to lubricate and cool the engine can improve the efficiency of the system due to the reduced mass and the benefits of using the substance to cool the engine rather than relying on air cooling, which may have problems traveling throughout the engine.

[0037] Additional embodiments of the electric engine may include various components to ensure that any flammable fluids are monitored and prevented from entering certain sections of the electric engine. Some embodiments may include an electric engine with a wet area housing, which may be defined by a gearbox, motor, and / or heat exchanger. In some embodiments, the electric engine may have up to four liters or more of air in contact with the engine oil within the motor-gearbox housing. For example, depending on factors such as the size and number of propellers or the aircraft's payload, the electric engine may have up to five, six, eight, ten, or twenty liters of air in contact with the engine oil within the motor-gearbox housing. Embodiments of the motor-gearbox housing may utilize a ventilator to equalize internal and external pressures. Embodiments of the ventilator may include a ventilator that protrudes above nearby design features to prevent inadvertent ingress of external fluids. Additional embodiments may include a ventilator with a screen and a circuitous entry path to prevent the ingress of external debris. Embodiments may include inspection windows on both the tilt electric engine and the lift electric engine to facilitate inspection during maintenance for overfilling or underfilling of the oil.

[0038] Additional embodiments of the electric engine may include active protection features in the front and rear electric engines, such as monitoring internal temperatures throughout the engine operation, including oil temperature, stator winding assembly, inverter bulk capacitors, power modules, control board power modules, control board control processor, control board monitoring processor, internal hot spots, and various other locations throughout the engine. Embodiments may include overtemperature limits that take into account known fault temperatures and operating limits related to the auto-ignition temperature of the fluid. Some embodiments may include a high-voltage power system that may have a fuse at the high-voltage battery terminal that can irreversibly and quickly disconnect the engine electrical connection to mitigate an overcurrent event. This overcurrent protection may be activated when the current draw of the electric engine is greater than the overcurrent operation. Therefore, in some embodiments, a fault condition that results in an overcurrent may only result in a transient overheating, arcing, or sparking fault. Some embodiments may include a fire threat characterization test ignition source, which may be selected to be more severe than a short circuit that occurs in the electric engine and is disconnected by the engine fuse. In some embodiments, the inverter will detect AC overcurrent and isolate the wrong phase and / or will continuously monitor the input DC voltage and will apply protective action to keep the voltage below the overvoltage operating limit.

[0039] During takeoff, landing, hovering, and cruising, a VTOL aircraft's motors and associated control components can generate heat. This heat must be dissipated to prevent degradation or damage to the VTOL aircraft's motors, control components, and other components. For some types of VTOL aircraft, such as electric VTOL (eVTOL) aircraft, thermal management is also crucial to maintaining optimal energy efficiency for components powered by batteries, for example.

[0040] Some components may generate high heat loads only during certain operating periods. For example, some lift propellers may be used only during takeoff, landing, and hovering, and may be shut down during cruise. Thus, such lift propellers may generate high heat loads during takeoff, landing, and hovering, and little or no heat during cruise.

[0041] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which, unless otherwise specified, like numbers in different figures represent the same or similar elements. The embodiments set forth in the following description of the exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of apparatus and methods consistent with various aspects related to the subject matter recited in the appended claims.

[0042] In some embodiments, the VTOL aircraft described herein include at least one fixed wing, a plurality of lift propellers fixed to provide lift during takeoff, landing, and hovering, and a plurality of tilted propellers that can be tilted from a lift configuration for providing lift to a cruise configuration for providing the forward thrust required for the at least one fixed wing to provide lift to the aircraft. By configuring the VTOL aircraft so that a portion of the propulsion system is dedicated to lift and a portion of the propulsion system is used during both lift and forward flight, the aircraft can be lighter and have lower drag than VTOL aircraft with separate lift and propulsion systems, as well as VTOL aircraft that use all propulsion for both lift and forward flight. Winged VTOL aircraft with separate propulsion systems for vertical and forward propulsion essentially waste the forward propulsion system during vertical takeoff, landing, and hovering. In contrast, aircraft according to the principles described herein utilize the forward propulsion system during vertical takeoff and landing, which can result in an overall relatively light propulsion system. Winged VTOL aircraft that tilt all their propellers have limited locations for positioning propellers (propellers must be positioned forward and aft of the center of gravity, but their positioning is constrained by other propellers and the wing), which typically results in relatively few and therefore larger propellers. In contrast, a propulsion system based on the principles described herein can have relatively smaller, lighter, and lower-drag propellers. Thus, the aircraft in some embodiments described herein have an ideal balance between a dedicated lift propulsion system and a tiltable propulsion system.

[0043] As used herein, the term "tilt propeller" refers to a variable pitch propeller configured to provide thrust for vertical lift and forward propulsion by changing the pitch of the propeller. The term "lift propeller" may refer to a fixed pitch propeller configured to provide thrust for vertical lift.

[0044] Figure 1 and Figure 2 A VTOL aircraft 100 is shown in a cruise configuration and a vertical takeoff, landing, and hovering configuration (also referred to herein as a "lift" configuration), respectively, consistent with an embodiment of the present disclosure. The aircraft 100 may include a fuselage 102, wings 104 mounted to the fuselage 102, and one or more rear stabilizers 106 mounted to the rear of the fuselage 102. A plurality of lift propellers 112 may be mounted to the wings 104 and may be configured to provide lift for vertical takeoff, landing, and hovering. A plurality of tilt propellers 114 may be mounted to the wings 104 and may be tiltable between a lift configuration in which the plurality of tilt propellers provide a portion of the lift required for vertical takeoff, landing, and hovering, as shown in FIG. 1 . Figure 2 As shown, in the cruise configuration the plurality of tilted propellers provide forward thrust to the aircraft 100 for horizontal flight, as shown in FIG. Figure 1 As used herein, a tilt-propeller lift configuration refers to any tilt-propeller orientation in which the tilt-propeller thrust primarily provides lift to the aircraft, and a tilt-propeller cruise configuration refers to any tilt-propeller orientation in which the tilt-propeller thrust primarily provides forward thrust to the aircraft.

[0045] In some embodiments, lift propellers 112 can be configured to provide only lift, with all propulsion being provided by the tilt propellers. Thus, lift propellers 112 can be in a fixed position and can generate thrust only during takeoff, landing, and hovering. Meanwhile, tilt propellers 114 can be tilted to a lift configuration, where their thrust is directed downward to provide additional lift.

[0046] For forward flight, the tilt propellers 114 can be tilted from their lift configuration to their cruise configuration. In other words, the pitch of the tilt propellers 114 can be changed from a pitch in which the tilt propeller thrust is directed downward (to provide lift during vertical takeoff, landing, and hovering) to a pitch in which the tilt propeller thrust is directed rearward (to provide forward thrust to the aircraft 100). The tilt propellers can be tilted about an axis 118, which can be perpendicular to the forward direction of the aircraft 100. When the aircraft 100 is in full forward flight, lift can be provided entirely by the wings 104. Meanwhile, in the cruise configuration, the lift propellers 112 can be turned off. The blades 120 of the lift propellers 112 can be locked in a low drag position for aircraft cruising. In some embodiments, the lift propellers 112 can each have two blades 120 that can be locked for cruising in a minimum drag position in which one blade is directly in front of the other blade, such as Figure 1 In some embodiments, the lift propeller 112 has more than two blades. In some embodiments, the tilt propeller 114 includes more blades 116 than the lift propeller 112. For example, Figure 1 and Figure 2 As shown, lift propellers 112 may each include, for example, two blades, and pitch propellers 114 may each include, for example, five blades. In some embodiments, pitch propellers 114 may have, for example, 2 to 5 blades.

[0047] In some embodiments, the aircraft may include only one wing 104 on each side of the fuselage 102 (or a single wing extending across the entire aircraft), and at least a portion of the lift propellers 112 may be located behind the wings 104, and at least a portion of the tilt propellers 114 may be located in front of the wings 104. In some embodiments, all of the lift propellers 112 may be located behind the wings 104, and all of the tilt propellers 114 may be located in front of the wings 104. According to some embodiments, all of the lift propellers 112 and the tilt propellers 114 may be mounted to the wings—that is, none of the lift propellers or the tilt propellers are mounted to the fuselage. In some embodiments, all of the lift propellers 112 may be located behind the wings 104, and all of the tilt propellers 114 may be located in front of the wings 104. According to some embodiments, all of the lift propellers 112 and the tilt propellers 114 may be positioned inboard of the wing tips 109.

[0048] In some embodiments, the lift propeller 112 and the tilt propeller 114 can be mounted to the wing 104 via a boom 122. The boom 122 can be mounted below the wing 104, on top of the wing, and / or can be integrated into the wing profile. In some embodiments, each boom 122 can be mounted with one lift propeller 112 and one tilt propeller 114. The lift propeller 112 can be mounted at the rear end of the boom 122, and the tilt propeller 114 can be mounted at the front end of the boom 122. In some embodiments, the lift propeller 112 can be mounted in a fixed position on the boom 122. In some embodiments, the tilt propeller 114 can be mounted to the front end of the boom 122 via a hinge 124. The tilt propeller 114 can be mounted to the boom 122 so that the tilt propeller 114 is aligned with the main body of the boom 122 when in its cruise configuration, thereby forming a continuous extension of the front end of the boom 122 that minimizes drag in forward flight.

[0049] In some embodiments, aircraft 100 may include, for example, one wing on each side of fuselage 102 or a single wing extending across the aircraft. According to some embodiments, at least one wing 104 is a high wing mounted to the upper side of fuselage 102. According to some embodiments, the wing includes control surfaces, such as flaps and / or ailerons. According to some embodiments, the wing may have a curved wing tip 109 for reducing drag during forward flight.

[0050] In some embodiments, the rear stabilizer 106 includes control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing can have any suitable design. In some embodiments, the wing has a tapered leading edge 123, such as, for example, Figure 1In some embodiments, the wing has a tapered trailing edge, such as Figure 3 As shown in the embodiment of Figure 3 In an embodiment, the wing may have a substantially straight leading edge 127 in a central section of the wing 104 .

[0051] Aircraft 100 may include at least one door 110 for passengers to enter and exit. In some embodiments, door 110 may be located below and in front of wing 104, such as Figure 2 shown.

[0052] In some embodiments, a lift propeller 112 or a tilt propeller 114 can be yawed relative to at least one other lift propeller 112 or tilt propeller 114. As used herein, yaw refers to the relative orientation of the axis of rotation of the lift propeller / tilt propeller about a line parallel to the forward-aft direction, similar to the roll degree of freedom of an aircraft. The yaw of the lift propeller and / or tilt propeller can be yawed by orienting the plane of rotation of the lift propeller / tilt propeller disk (the blades plus the portion of the propeller to which the blades are mounted) so as not to intersect critical portions of the aircraft (such areas of the fuselage where personnel may be located, critical flight control systems, batteries, adjacent propellers, etc.) or other propeller disks to help minimize damage from a propeller blowout and can provide enhanced yaw control during flight.

[0053] The lift propellers 112 may be deflected in any suitable manner and combination. In some embodiments, the lift propellers 112 may be deflected in accordance with corresponding pitch propellers. For example, Figure 3 As shown, innermost lift propeller 112a can be deflected by the same amount and in the same direction as innermost tilt propeller 114a. Similarly, lift propellers 112b and 112c can be deflected similarly to corresponding tilt propellers 114b and 114c, respectively. Any suitable combination of deflection and / or non-deflection of lift propellers relative to each other and relative to the tilt propellers can be used to achieve desired performance characteristics.

[0054] Further discussion of VTOL aircraft can be found in U.S. Patent Publication No. 2021 / 0362849, the entire contents of which are incorporated herein by reference in their entirety.

[0055] As mentioned above, the motors and associated control components of a VTOL aircraft can generate heat during operation. This heat must be dissipated to prevent degradation or damage to the motors, control components, and other elements of the VTOL aircraft. For example, cooling can be achieved by directing airflow over a heating component. The heating component can be, for example, a motor or other heat-generating component, or it can be, for example, a heat exchanger configured to receive heat from a heat-generating component via a liquid heat exchange medium. However, diverting the constant air flow outside the VTOL can create unwanted drag and other forces that can slow the aircraft. For example, the boom can be provided with a scoop or large hole to collect enough air to meet maximum cooling requirements. Such a scoop or large hole can create drag. In addition, large holes or other openings can create weak points in the VTOL structure and weaken the overall structural integrity. This can increase the risk of damage or failure, or require strengthening the structure elsewhere, which can result in an increase in the weight of the VTOL aircraft.

[0056] Furthermore, some components may generate high heat loads only during their operating periods. For example, a lift propeller may only operate in a lift configuration during the lift phase and therefore require significant cooling only during the lift phase. The lift configuration may be a period when drag is not a primary concern for the lift propeller. However, during the cruise configuration, the situation may be reversed: drag may be a key issue, while cooling the lift propeller may not be.

[0057] Finally, air-cooled components may be exposed to dirt, debris, and other contaminants from the airstream. This contamination can degrade the components, leading to failure and shortening their lifespan. Therefore, it may be desirable to provide a lift motor cooling path and motor configuration that allows for efficient cooling during lift without incurring unacceptable drag penalties during cruise and without contaminating or damaging sensitive components of the VTOL aircraft.

[0058] Figure 4A - Figure C shows a portion of a VTOL aircraft 400 consistent with an embodiment of the present disclosure. The VTOL aircraft 400 may be similar to Figure 1-Figure 3 VTOL aircraft 100. Figure 1-Figure 3 Similar components in Figure 4A - Elements in Figure C may be labeled with corresponding numbers with 4 as the leading digit. For example, in some embodiments, Figure 4A The boom 422 may be similar to Figure 1-Figure 3 The boom is 122.

[0059] exist Figure 4AIn FIG. 4 , two booms 422 are depicted on wing 404, with the lower boom shown in an exploded view with motor assembly 430 exposed. Upper boom 422 is shown as seen in operation with fairing 425 covering its motor assembly. Motor assembly 430 may be coupled to boom 422 (e.g., via mounting 434) via Figure 4B Each motor assembly 430 may be configured to drive its own lift propeller 412 , which includes blades 420 secured to a hub 431 .

[0060] Boom 422 is a structural component because it can significantly contribute to the structural integrity of VTOL aircraft 400 and provide structural support for motor assembly 430 and lift propeller 412. In other words, boom 422 is an elongated support structure for motor assembly 430, lift propeller 412, fairing 425, or other components of VTOL aircraft 400. Fairing 425 is an aerodynamic component. For example, fairing 425 can be shaped to provide aerodynamic advantages, such as reduced drag, but does not significantly contribute to the structural integrity of VTOL aircraft 400 or provide structural support for motor assembly 430 or lift propeller 412.

[0061] The fairing 425 can also be configured to direct cooling air to the motor assembly 430. For example, the fairing 425 can include an air inlet 440 on its top side. The air inlet 440 can be a hole located at a favorable area on the fairing 425 so as to receive a large volume of cooling air from the downwash (i.e., the air flow forced downward by the rotation of the blades 420) from the lift propeller 412 during operation. For example, the inlet 440 can be placed below the path of the blades 420, at a radial distance from the hub 431, at which the pressure or flow from the downwash is higher. In addition, the inlet 440 can have a narrow slot shape that is elongated substantially along the longitudinal axis of the boom 422 so as to span a range of radial distances from the hub 431 and capture a larger volume of downwash from the lift propeller 412. Finally, as described below with respect to Figure 6D As further discussed, the air inlet 440 may be laterally offset from the longitudinal axis of the boom 422 to place the inlet at an area of ​​localized highest downwash pressure or mass flow.

[0062] Because inlet 440 does not need to face the forward direction of flight in order to collect sufficient air flow, it can have certain aerodynamic design advantages over conventional scoops or other apertures. For example, inlet 440 can be located on a downwardly inclined surface of fairing 425, such as on the tail side of lift propeller 412. In addition, a bump, lip, or other aerodynamic feature can be formed on the front side of air inlet 440 to reduce drag during the cruise configuration without interfering with the cooling function of air inlet 440 during the lift configuration.

[0063] In addition to the location and shape of air inlet 440, since air inlet 440 is not placed in a structural component of VTOL 400, its size can be advantageously increased. For example, when large holes or other openings are cut into a structural component such as boom 422, they may pose concerns about the structural integrity of VTOL aircraft 400. When large openings are cut into non-structural surfaces such as fairing 425, this may not be a critical issue, but other considerations (e.g., drag) may still exist. However, in some embodiments, boom 422 may include air inlet 440, or may include an inlet instead of or in addition to inlet 440.

[0064] Figure 4B Shown is consistent with the embodiment of the present disclosure Figure 4A 4. The motor assembly 430 can be mounted to and supported by the boom 422 via a mounting bracket 434. The motor assembly 430 can be further coupled to the hub 431 and blades 420 of the lift propeller 412 (e.g., Figure 4A As shown, Figure 4B 4). Motor assembly 430 may be configured to rotate shaft 432 at a variable speed during a lift phase of VTOL aircraft 400 to generate vertical thrust at lift propeller 412 in a lift configuration. Motor assembly 430 may be configured to position blades 420 in a fixed, low-drag cruise configuration (e.g., as shown) during a cruise phase of VTOL aircraft 400. Figure 4A shown).

[0065] Motor assembly 430 may include, for example, a motor 435, a gearbox 436, and an inverter 437. Motor assembly 426 may further include a housing 426 surrounding motor 435, gearbox 436, and inverter 437. For example, housing 426 may include a substantially form-fitting outer shell surrounding components 435-437 of motor assembly 430. Because motor 435, gearbox 436, and inverter 437 are enclosed within housing 426, the internal workings of these components are not shown here. Housing 426 may prevent dust, debris, or other contaminants contained in the cooling air flow from negatively impacting components 435-437. Motor assembly 430 may further include heat transfer elements 433 and 438 positioned externally of housing 426 to thermally couple components 435-437 of motor assembly 430 to, for example, the cooling air flow. For example, cooling fins 438 may be coupled to housing 426 to surround motor 435 at the upper portion of motor assembly 430. In addition, heat exchanger 433 can be coupled to housing 426 at a lower portion of motor assembly 430 near inverter 437. Thus, in some embodiments, the motor assembly can include a hybrid cooling power engine having a first portion and a second portion that can be cooled separately. In some embodiments, heat exchanger 433 or portions of cooling fins 438 can extend within housing 426 in a manner that maintains a substantial seal from the outside air.

[0066] It should be understood that Figure 4B The spatial relationships between the various components of motor assembly 430 shown are provided by way of example and need not always be arranged in this manner. For example, in some embodiments, gearbox 436 may not be located below motor 435, or neither component may be located above or below the other. In general, as will be appreciated by those of ordinary skill in the art, the various components of motor assembly 430 may be arranged in a variety of configurations. Furthermore, the motor assembly may include additional components, or one or more components discussed herein may be omitted.

[0067] Furthermore, not all components need to be arranged symmetrically. For example, the motor 435 and the gearbox 436 can be configured to share the same longitudinal axis. For example, the longitudinal axis can correspond to the longitudinal axis of their propellers ( Figure 4B 436). Also, inverter 437 may not share a longitudinal axis with motor 435 and gearbox 436. For example, inverter 437 may be positioned offset from the other components of motor assembly 430 or positioned on one side of motor assembly 430. Generally, inverter 437 may be positioned within housing 426 in any suitable arrangement.

[0068] In addition, the motor assembly 430 may include redundancy to ensure proper operation in the event of a failure of one or more components. For example, the motor 435 may include a rotor surrounded by multiple redundant stators. The multiple stators may be configured to operate simultaneously in conjunction with each other, as well as to operate independently in the event of a failure. Similarly, the inverter 437 may include multiple stages. In some embodiments, the inverter 437 may include a dual-stage inverter, or may include more than two stages.

[0069] Heat exchanger 433 can be configured to receive a circulating heat exchange medium from within motor assembly 430. For example, the heat exchange medium can include oil, and the oil can be used to lubricate and cool components of motor assembly 430. The oil can circulate through a lubricated heat exchange flow path that includes one or more components of motor assembly 430, such as motor 435, gearbox 436, inverter 437, and heat exchanger 433. The lubricated heat exchange flow path can be advantageously minimized by positioning heat exchanger 433 near housing 426, thereby minimizing the volume (and weight) of material required to implement cooling and lubrication functions. Furthermore, the lubricated heat exchange flow path can reduce the need for hoses, connectors, and other components that can increase complexity and weight and increase the risk of failure. Thus, motor assembly 430 can include a substantially sealed hybrid cooling system that is configured to utilize one or more cooling air flow paths for multiple heat-generating portions of motor assembly 430, as further described below.

[0070] Figure 4C Shown is consistent with the embodiment of the present disclosure Figure 4A or Figure 4B 4. An example close-up view of the housing 426 of the motor assembly 430 of FIG. The housing 426 may include a motor housing 427, a separator plate 428, and an inverter housing or controller housing 429.

[0071] The motor housing 427 can surround and seal the upper components of the motor assembly 430, such as the motor 435 and the gearbox 436. A coolant, such as oil, can be circulated through the motor housing 427 to lubricate and cool the components of the motor 435 and the gearbox 436. The lower surface of the motor housing 427 can be sealed by a separator plate 428. For example, the separator plate 428 can include a bell-shaped end cap plate for closing the motor housing 427.

[0072] Inverter housing 429 can surround and seal lower components of motor assembly 430, such as inverter 437. Inverter 437 can include, for example, electronic circuit boards and other control components configured to control the operation of motor assembly 430. Thus, the inverter can include a lift propeller controller, and inverter housing 429 can alternatively be referred to as controller housing 429. Controller housing 429 can be isolated from the oil or other coolant of the motor housing by separator plate 428. For example, separator plate 428 can include a thermal plate that is used to enclose controller housing 429 and thermally couple it to the oil or other coolant.

[0073] The separator plate 428 may include one or more plates sandwiched together and disposed between the motor housing 427 and the controller housing 429. For example, in some embodiments, the separator plate 428 may include a bell-shaped end cap and a thermal plate as described above, sandwiched together between the motor housing 427 and the controller housing 429. The separator plate 428 may isolate the interior spaces of the motor housing 427 and the controller housing 429 from each other and from the external environment outside the housing 426. In some embodiments, one or more of the sandwich plates of the separator plate 428 may include grooves, holes, or other conduits configured to distribute oil or other coolant in a planar direction of the separator plate 428.

[0074] In some embodiments, the separator plate 428 may include an integral mounting bracket for supporting the heat exchanger 433. The heat exchanger 433 may include, for example, folded fins or other types of heat exchangers. Oil or other coolant that has been heated by the motor 435, gearbox 436, or inverter 437 can be circulated through the fins of the heat exchanger 433 via the internal conduits of the heat exchanger 433. The inlet and outlet for the internal conduits can be coupled to the outlet and inlet of the holes or grooves of the separator plate 428, respectively. In this way, the heated oil (or other coolant) can carry heat from the housing 426 to the fins of the heat exchanger 433, where the heat can be transferred to the cooling air flow traveling through the fins. Thus, the entire motor assembly can be effectively cooled without exposing sensitive components to the external environment.

[0075] The motor housing 427, the partition plate 428, and the inverter housing 429 may be formed of a lightweight and rigid material, such as a material having high thermal conductivity, such as a metal such as aluminum or copper, a ceramic such as silicon carbide, or another suitable material.

[0076] Figure 5A-Figure 5N A schematic illustration of example oil and air flow paths in and around a motor assembly of a VTOL aircraft consistent with embodiments of the present disclosure is provided. The VTOL aircraft may be similar to Figure 1-Figure 3 VTOL aircraft 100 or Figure 4A- VTOL aircraft 400 in Figure C. Figure 5A-Figure 5N Zhongyu Figures 1-4C Elements similar to the elements in the figure may be labeled with corresponding numbers using 5 as the leading digit and ending with the corresponding alphanumeric letter. For example, in some embodiments, Figure 5A The fairing 525a may be similar to Figure 4A Fairing 425 or Figure 5B Fairing 525b. Figure 5A-Figure 5N The solid arrow lines in FIG. 1 may represent oil (or other heat exchange medium) flow paths, while the dashed arrow lines may represent cooling air flow paths.

[0077] Figure 5AA motor assembly 530a and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure are schematically depicted. The motor assembly 530a may include components housed within a housing 526a, such as a motor 535a, a gearbox 536a, and an inverter 537a. The housing 526a may include a motor housing 527a, a separator plate 528a, and a controller housing 529a. The motor housing 527a may surround and seal components such as the motor 535a and the gearbox 536a. The controller housing 529a may surround and seal the inverter 537a. The motor assembly 530a may further include a heat exchanger 533a that is thermally coupled to the components 535a-537a via a lubricating heat exchange oil flow path (represented by a solid line). In some embodiments, the heat exchanger 433 may be supported by a mounting bracket or other extension of the separator plate 528a. The separator plate 528a can extend beyond the motor housing 527a and the controller housing 529a, so that the separator plate 528a can both support the heat exchanger 533a and seal the motor housing 527a and the controller housing 529a. The separator plate 528a can further include holes, grooves, or other conduits to circulate oil (or other coolant) from the motor housing 527a to the heat exchanger 533a. The middle portion 528a can further thermally couple the controller housing 529a to the oil through heat conduction. Thus, the lubricating heat exchange oil flow path can lubricate the components 535a-537a and / or absorb heat generated by the components. The heat absorbed by the oil can be carried to the heat exchanger 533a, where it can be transferred to the incoming air (indicated by the dotted lines). For example, the air can pass through fins or other pathways in the heat exchanger 533a. The fins or other pathways can be configured to maximize the surface contact area between the heat exchanger and the air flow while maintaining an acceptable limit for the air pressure drop across the heat exchanger. Air flow can enter the internal chamber through an inlet 540a in the surface of the fairing 525a. The internal chamber can be formed by the fairing 525a and can be cooperating with, for example, the end of a boom (not shown) to which the fairing 525a is attached to enclose the motor assembly 530a. The air flow can be forced into the inlet, for example, as downwash from propeller blades (not shown) above the inlet 540a. The air can exit the heat exchanger 533a and exit the chamber, for example, through one or more air outlets (not shown), without entering or passing through the housing 526a.

[0078] The lubricating heat exchange oil flow path is shown at a high level of generalization as a simple loop. However, it should be understood that the oil flow path may include branches, sub-loops, or other segmented paths. In general, the oil can be circulated in any manner that effectively lubricates and cools the various components of the motor assembly.

[0079] Figure 5B Schematically depicts a motor assembly 530b and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figure 5A Corresponding elements in the drawings may have the same reference numerals, and their descriptions may be omitted here. Figure 5B In FIG. 5 , the motor assembly 530b may further include an additional heat transfer element 538b coupled to the housing 526b. For example, the heat transfer element 538b may include cooling fins attached to the exterior of the motor housing 527b, similar to the Figure 4B The configuration shown. The air flow from the inlet 540b can be divided into bifurcated air flow paths, wherein the first air flow path passes through the heat transfer element 538b and the second air flow path passes through the heat exchanger 533b. The first air flow path can exit through the outlet (not shown) without passing through the heat exchanger 533a. Figure 5B , the first air flow path is shown as passing behind the heat exchanger 533b. However, this is merely a schematic diagram showing that the two air flow paths are not co-linear. The second air flow path can exit through the same outlet or a different outlet without passing through the heat transfer element 538a. The bifurcated flow path can enable the cooling air flow to be directed to the section of the motor assembly 530b with the highest heat load. In addition, providing different flow paths can allow each section of the motor assembly 530b to be cooled regardless of the heat load applied to the different flow paths of the different sections. For example, when the motor 535b is very hot and a large amount of heat is transferred to the first flow path through the heat transfer element 538b, the heat exchanger 533b can continue to receive a relatively low temperature air flow from the second flow path because the air flow does not encounter the heat transfer element 538b.

[0080] Figure 5C Schematically depicts a motor assembly 530c and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figure 5A-5B Corresponding elements in the drawings may have the same reference numerals, and their descriptions may be omitted here. Figure 5C In the embodiment of the present invention, the diverging flow paths can rejoin before entering the heat exchanger 533c. This can have the advantage of providing a greater air flow to the heat exchanger 533c at the expense of the risk of heat transfer between the heat transfer element 538c and the heat exchanger 533c. In some embodiments, various parameters (e.g., the expected mass flow rate and temperature of the incoming air, the expected heat load from the heat transfer element 538c and the heat exchanger 533c, etc.) can make this risk acceptable.

[0081] Figure 5D Schematically depicts a motor assembly 530d and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figures 5A-5C Elements corresponding to the elements in the figure may have the same figure numbers, and their descriptions may be omitted here. Figure 5DA single air flow path is depicted through both heat transfer element 533d and heat exchanger 533d. This arrangement can provide full cooling air flow to both element 533d and element 538d and can provide a simpler internal structure for the chamber within fairing 525d.

[0082] Figure 5E Schematically depicts a motor assembly 530e and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figures 5A-5D Elements corresponding to the elements in the figure may have the same figure numbers, and their descriptions may be omitted here. Figure 5E A bifurcated airflow path is depicted, wherein a first airflow path can exit through a first inlet on a first side of the chamber, and a second airflow path can exit through a second inlet on a second side of the chamber. For example, as described below, the first airflow path can pass through the cooling fins of, for example, heat transfer element 538e, to remove heat transferred from the upper portion of motor assembly 530e, such as heat transferred from motor 535e. The first airflow path can then exit through, for example, the top side of fairing 525e at a location with a relatively lower pressure than that found at inlet 540e. Simultaneously, the second airflow path can pass through, for example, heat exchanger 533e, to remove heat transferred from the lower portion of motor assembly 530e, such as heat transferred from inverter 537e, or heat transferred from all components 535e-537e, via heated oil. The second airflow path can then exit through, for example, the bottom side of fairing 525e. Figure 5E The arrangement can provide improved heat separation between the two flow paths and can provide a shorter travel distance within each air flow path, so that the heated air leaves the chamber more quickly. In addition, Figure 5E The arrangement may allow the system to utilize multiple low pressure outlet areas to improve the overall air flow through the chamber.

[0083] Figure 5F Schematically depicts a motor assembly 530f and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figures 5A-5E Elements corresponding to the elements in the figure may have the same figure numbers, and their descriptions may be omitted here. Figure 5F The controller 537f for the motor assembly 530f is depicted as being located within the sealed housing 526f and thermally coupled to an external heat exchanger 533f. In some embodiments, the housing 526f may also house other components, such as other parts of the motor assembly 530f. Heat from the controller 537f may be transferred to oil or other coolant circulating within the housing 526f and subsequently to a cooling air flow through the heat exchanger 533f.

[0084] Figure 5G Schematically depicts a motor assembly 530g and surrounding elements of a VTOL aircraft consistent with an embodiment of the present disclosure. Figures 5A-5F Elements corresponding to the elements in the figure may have the same figure numbers, and their descriptions may be omitted here. Figure 5G Depicts the Figure 5A 545g. The embodiment of the present invention is similar to the embodiment of the present invention, in which the cooling air flow path is confined within the channel 545g. For example, the channel 545g may include baffles or ducts configured to define a channel to close the air flow cooling path between the inlet 540g and the inlet side of the heat exchanger 533g. In addition, the channel 545g can continue from the outlet side of the heat exchanger 533 to the air outlet (not shown) in the cowling 525g. In some embodiments, the channel 545g can partially or completely close the cooling air flow path and further isolate the downwash in the air flow path from the enclosed components of the motor assembly within the housing 526g. Figure 5G The arrangement can advantageously provide improved flow rate and reduced lumen pressure loss, as described below with respect to Figure 6E Further discussion.

[0085] Figure 5H-5N Schematically depicts further configurations of a motor assembly and surrounding elements of a VTOL aircraft consistent with embodiments of the present disclosure. Figure 5A-5G Elements corresponding to the elements in the figure may have the same figure numbers, and their descriptions may be omitted here. Figure 5H-5N The arrangement basically corresponds to Figure 5A-5G However, in Figure 5H-5N In each of the embodiments, the inlet 540 may be located within the boom 522 rather than within the fairing 525. Thus, Figure 5H Basically corresponds to Figure 5A , where the inlet 540h is located in the boom 522h rather than in the fairing. Figure 5I Basically corresponds to Figure 5B , where the inlet 540i is located in the boom 522i rather than in the fairing. Figure 5J Basically corresponds to Figure 5C , where the inlet 540j is located in the boom 522j rather than in the fairing. Figure 5K Basically corresponds to Figure 5D , where the inlet 540k is located in the boom 522k rather than in the fairing. Figure 5L Basically corresponds to Figure 5E , where the inlet 5401 is located in the boom 5221 rather than in the fairing. Figure 5M Basically corresponds to Figure 5F , where the inlet 540m is located in the boom 522m rather than in the fairing. Figure 5NBasically corresponds to Figure 5G , where the inlet 540n is located in the boom 522n rather than in the fairing.

[0086] In some embodiments, Figure 5H-5N The surfaces of the booms 522h-522n in the embodiment may replace the fairing 525, and the inlets 540h-540n may be located in substantially the same position as they would otherwise be. For example, the tail profile region containing the inlets 540h-540n may in some embodiments be a fairing (e.g., as Figure 4A The fairing 425 shown), the region may alternatively form part of the boom and may be part of a structural surface that contributes to the structural integrity of the VTOL aircraft or supports the motor assembly 530. Alternatively, the inlets 540h-540n may be placed at a different location away from the fairing. For example, Figure 5H-5N The arrangement may still include a fairing on the tail profile area, but the inlets 540h-540n may be placed elsewhere on the surface of the booms 522h-522n. In some embodiments, the fairing may occupy more or less of the total surface profile formed by the boom and fairing combination, and the inlet / outlet may be formed in the fairing, the boom, or both. In some embodiments, the inlet or outlet may straddle the boundary between the boom and the fairing.

[0087] Figures 6A-6E 1 shows an example air flow path arrangement in a portion of a VTOL aircraft 600a-600e consistent with an embodiment of the present disclosure. The VTOL aircraft 600a-600e may be, for example, similar to Figure 1-5N Any of the VTOL aircraft 100, 400 or 500. Figure 1-5N Similar components in Figures 6A-6E The elements in can be marked with corresponding numbers using 6 as the leading digit. For example, in some embodiments, Figure 6A The entry 640 can be similar to Figure 4A Entrance 440.

[0088] Figure 6A An example bifurcated air flow path arrangement is shown in a portion of a VTOL aircraft 600a consistent with an embodiment of the present disclosure. Air flow from, for example, downwash from a lift propeller blade (not shown) can enter the fairing 625 through an inlet 640, as indicated by the arrows. The inlet 640 can be located in an area where pressure is relatively high due to the downwash. A baffle 645 can distribute the air flow into an upper flow path 643 and a lower flow path 644. Alternatively, a separate inlet can be provided for each of the motor and lower flow path.

[0089] The air in the lower flow path 644 can be directed by the baffle 645 through the heat exchanger 633. The heat exchanger 633 can be connected to the heat exchanger 633 by, for example, Figure 5A-Figure 5N The oil flow path discussed receives heat from components of the motor assembly 630, such as the motor 635, gearbox 636, or inverter 637. Cooling air in the lower flow path 644 can absorb heat from the heat exchanger 633 and exit the cowling 625 at the lower outlet 642. In this way, a source of cool air can be constantly supplied to the target heat load during the lift phase, when heat generation is at its maximum. At the same time, sensitive components within the motor assembly 630 can be protected from impurities within the air flow by the housing.

[0090] As in Figure 6A As viewed from above in the lower figure of , the inlet 640 and the outlet 642 can have different shapes and orientations. For example, the inlet 641 can be elongated substantially parallel to the longitudinal axis of the boom 622 to, for example, span a range of radial distances from the hub 631 and capture a large amount of downwash from the lift propeller blades. In some embodiments, the inlet 640 can include an asymmetry. For example, the inlet 640 can be offset from the longitudinal axis, can be elongated substantially at an angle to the longitudinal axis, or can include a shape that is asymmetric with respect to the longitudinal axis. The asymmetry can depend on the unique downwash distribution that is expected for the particular boom to which the inlet 640 belongs. For example, the lift propeller can be configured to rotate in one of two rotational directions, thereby creating an asymmetry in the downwash distribution on the upper surface of the fairing 625. In addition, the lift propeller can be deflected at different angles, such as Figure 3 Thus, the location, shape, and orientation of inlet 640 can be selected to correspond to these asymmetries and their resulting desired downwash flow distribution.

[0091] In some embodiments, the outlet 642 can be elongated substantially perpendicular to the longitudinal axis. The outlet 642 can be arranged so that heated air can easily escape from the heat exchanger 633. For example, the outlet 642 can be shaped and oriented to substantially match the outlet path of the heat exchanger 633. In some embodiments, the outlet 642 may not exactly correspond to the shape or size of the outlet side of the heat exchanger 633.

[0092] In some embodiments, as described below with respect to Figure 6E As discussed, baffle 645 can define a channel configured to direct air between inlets and outlets of different sizes or orientations. For example, baffle 645 can define a channel that matches the right portion of inlet 640 at the location of inlet 640 (e.g., at Figure 6AInstead of forming an open cavity in lower path 644, the channel may conform to the shape of the inlet side of heat exchanger 633 at the location on the inlet side of heat exchanger 633. The channel may continue from the outlet side of heat exchanger 633 and conform to the shape of the outlet side at that location. Finally, the channel may extend to outlet 642 and may substantially match the shape and orientation of outlet 642 at that location.

[0093] The air in the upper flow path 643 can be directed by the baffle 645 through the heat transfer element 638, such as cooling fins. The cooling fins 638 can transfer heat from the upper portion of the motor assembly (such as the motor 635) to the air. Figure 6A As seen in the lower figure in FIG, the air in the upper flow path 643 can be directed to surround the cooling fins 638 and the motor 635 to optimize heat transfer. The heated air can then exit the cowling 625 through the upper outlet 641.

[0094] The upper outlet 641 surrounds the axis 632 and may exit the fairing 625 at an area of ​​relatively lower pressure compared to the inlet 640. The downwash from the propeller blades above the fairing may vary with radial distance from the hub 631, with the downwash pressure in the central region of the upper outlet 641 being significantly lower than the downwash pressure in the region of the inlet 640. This is particularly true in the area directly below the hub 631, which may not experience any direct downwash due to rotation. Therefore, in some embodiments, the outlet 641 may be located completely or partially below the hub 631. Additionally, the use of an upper outlet may allow the flow path to utilize convection created by the heated air at the cooling fins 638 to increase the upwash at the upper outlet 641. In this way, the two flow paths may remain completely separated from the inlet to the outlet. Figure 6A The flow path arrangement may allow full utilization of multiple low pressure regions in a lift configuration during the lift phase.

[0095] In addition, the profiles of the inlet and outlet can be optimized to reduce drag during the cruise phase without significantly affecting air flow during the lift phase. For example, outlet 641 can be configured to surround shaft 632 or hub 631 in a skewed elliptical shape, for example. Outlet 641 can have a larger opening on the aft side of shaft 632 than on the forward side, or can include a lip or other aerodynamic features on its forward side to minimize cruise drag while allowing heated air to easily escape during the lift phase.

[0096] Figure 6B An example single flow path in a VTOL aircraft 600b is shown consistent with an embodiment of the present disclosure. Figure 6ACorresponding elements in the drawings may have the same reference numerals, and their descriptions may be omitted here. Figure 6B In FIG. 6 , the entire air flow from the inlet 640 can be directed through multiple heat load sources in the motor assembly 630. Thus, the air flow can pass through the upper flow path 643 and the lower flow path 644 without bifurcation. For example, as in FIG. Figure 6B As seen in the upper and lower figures of FIG, baffle 645 can extend beyond the aft side of inlet 640, leaving the entire inlet undivided. This arrangement can advantageously provide more cooling air flow to each component. Additionally, eliminating upper outlet 641 can allow for more air flow to be directed through fairing 625 to heat exchanger 633. In some embodiments, outlet 641 can alternatively be configured as a secondary inlet. For example, as described below with respect to Figure 8-9B As discussed, the lift propeller may be provided with auxiliary features configured to direct additional cooling air into the secondary inlet about shaft 632 .

[0097] Figure 6C VTOL aircraft 600c consistent with an embodiment of the present disclosure is shown. Figure 6B Another variation of a similar example flow path arrangement. Elements corresponding to the above elements may have the same reference numerals, and their descriptions may be omitted here. Figure 6C , the upper flow path may be restricted to direct the air flow to the upper portion of the cooling fins 638. The baffle 645 may be configured with a manifold or other apertures for directing air into the cooling fins 638. For example, Figure 6C As shown by the radially inward arrows in the lower figure, the air flow from the upper path 643 can flow around the cooling fins 638 and flow down along the cooling fins into the lower flow path 644. Then, when the air flow proceeds to the heat exchanger 633 and the lower outlet 642, the air flow can bypass the outside of the motor assembly. In this way, the cooling air can be in close and continuous contact with the heat-generating area of ​​the motor assembly 630 for effective heat transfer. In some embodiments, as Figure 6C As shown, the width of the air inlet 640 in the cross-section of the fairing may be greater than 50% of the width of the fairing.

[0098] Figure 6DAn example inlet arrangement in a portion of a VTOL aircraft 600d consistent with embodiments of the present disclosure is shown. Inlet 640 may include multiple inlets 640a and 640b. Inlets 640a-640b may correspond to the same or different flow paths. For example, in some embodiments, first inlet 640a may direct airflow to a first flow path, and second inlet 640b may direct air to a second flow path. In some embodiments, both inlets 640a and 640b may direct air to one or more flow paths. In some embodiments, there may be more than two inlets.

[0099] Multiple inlets 640a-640b can be arranged to correspond to the downwash distribution of the specific boom 622 to which the inlets 640a-640b belong. For example, as shown by the arrows, the downwash from the propeller (not shown) above the boom 622 and the fairing 625 can have a vortex component based on its direction of rotation. This vortex component can lead to a downwash distribution that is more advantageously collected by the asymmetric arrangement of one or more inlets 640a-640b relative to the longitudinal axis LA of the boom 622. For example, the inlets 640a-640b can be offset from the longitudinal axis LA so as to be located in the area of ​​maximum downwash, or to utilize the vortex component. The inlets 640a-640b can be offset to different sides of the longitudinal axis LA. For example, the downwash distribution can have a complex or curved shape along the upper surface of the fairing 625. The first inlet 640a can be located at a first radial distance from the hub 631.

[0100] The vortex component can be further used, for example, to generate a desired flow direction within the fairing 625 or to actuate a louver door, as described below. The offset or other asymmetry can vary depending on the characteristics of each boom 622, such as the direction of blade rotation or the deflection angle. For example, a first boom may include a first lift propeller configured to rotate in a first direction. One or more inlets on the first boom may be offset from its longitudinal axis in the first direction. A second boom may include a second lift propeller configured to rotate in a second direction. One or more inlets on the second boom may be offset from its longitudinal axis in the second direction.

[0101] Figure 6E An example single flow path in a VTOL aircraft 600e is shown consistent with an embodiment of the present disclosure. Figures 6A-6D Corresponding elements in the drawings may have the same reference numerals, and their descriptions may be omitted here. Figure 6EIn FIG. 6 , baffle 645 can define a channel for directing airflow to heat exchanger 633. For example, baffle 645 can include a funnel-shaped channel. This channel can have a curved inner surface or flat sides. In some embodiments, the shape of the channel can substantially conform to the shapes of the various inlets and outlets to which it is connected. For example, the channel formed by baffle 645 can substantially conform to the contours of inlet 640 at the location of inlet 640 and substantially conform to the contours of outlet 642 at the location of outlet 642. Furthermore, the channel formed by baffle 645 can substantially conform to the contours of the inlet and outlet sides of heat exchanger 633 at both the inlet and outlet locations of heat exchanger 633. Thus, large airflows can be captured by arranging inlet 640 in any desired size, shape, and orientation. Regardless of the selected size, shape, and orientation, the airflow can be efficiently funneled into the fins of heat exchanger 633 with minimal turbulence and minimal internal pressure loss. Therefore, configuring baffle 645 as a form-fitting channel allows for greater design freedom for other components of the cooling path.

[0102] In some embodiments, Figure 6E The arrangement may illustrate a component of a bifurcated flow path. For example, Figure 6E It can be shown in the above Figure 6A An example of the lower flow path 644 is seen in FIG.

[0103] Figure 7A FIG. B shows an example arrangement of portions of VTOL aircraft 700a-700b consistent with an embodiment of the present disclosure. VTOL aircraft 700a-700b may be similar to, for example, Figure 1-6E Any of the VTOL aircraft 100 , 400 , 500 or 600 . Figure 7A - In Figure B Figure 1-6E Elements similar to the elements in can be marked with corresponding numbers using 7 as the leading digit. For example, in some embodiments, Figure 7A The entry 740 can be similar to Figure 4A Entrance 440.

[0104] exist Figure 7AInlet 740 may include a door 746 configured to optimize aerodynamic requirements between lift and cruise configurations. For example, door 746 may be configured to open during lift configuration to allow air into inlet 740 and close during cruise configuration to reduce drag. Door 746 may include a lip or other features that allow door 746 to be forced open by the vortex component of the downwash from blades 720. Hinge 747 may be arranged substantially perpendicular to the vortex component to facilitate opening and closing. Door 746 may include a spring or other biasing mechanism to keep the door tightly closed when blades 720 are closed during cruise configuration. Door 746 may close by gravity or be forced into a closed position by air during cruise. Door 746 may also be actuated between the open and closed positions by active control. Alternatively, door 746 may be fixed in position at an angle that captures sufficient airflow from the vortex component of the downwash. A fixed door may be configured to reduce drag by having a fully exposed aperture at inlet 740. For example, door 746 may have an angled opening that is wider on the aft side than on the forward side, or may include other profiles designed to reduce drag. For example, the opening created by door 746 may be angled to at least partially face the aft side of fairing 725 so that air is not blown into fairing 725 during forward motion in cruise.

[0105] Figure 7B Another variation of the arrangement of the example doors 746 in a VTOL aircraft 700b consistent with an embodiment of the present disclosure is shown. Figure 7A The arrangement in the VTOL aircraft 700a is similar. Elements corresponding to the above elements may have the same reference numerals, and their description may be omitted here. Figure 7B In the lift phase, the door 746 can be forced inward by the downwash flow. The door 746 can include a large portion of the upper surface of the fairing 725 so that when in the lift configuration, the flow path receives a large amount of air flow. For example, in the cross-sectional direction of the boom 722 or the fairing 725 perpendicular to the longitudinal axis of the boom 722, the width of the door 746 or the air inlet 740 can occupy 50%, 75%, 85% or 90% of the width of the upper surface of the fairing 725. In addition, as Figure 7B As shown, the length of the door 746 in the direction of the longitudinal axis of the boom 722 can be greater than the width of the door. The door 746 can then be biased or actuated to a closed position during cruising to reduce drag. The hinge 747 can be located at the aft end of the door 746, for example, as shown, or can be located along the Figure 7A One side positioning shown.

[0106] Figure 8800 are shown as example assist features on a lift propeller in a portion of a VTOL aircraft 800 consistent with an embodiment of the present disclosure. The VTOL aircraft 800 may be, for example, similar to Figure 1-7B Any of the VTOL aircraft 100 , 400 , 500 , 600 , or 700 . Figure 8 Zhongyu Figure 1-7B Elements similar to the elements in can be marked with corresponding numbers using 8 as the leading digit. For example, in some embodiments, Figure 8 The blade 820 may be similar to Figure 4A The blades are 420.

[0107] exist Figure 8 In the embodiment, the paddle 820 may include an internal passage 850 for directing additional cooling air into the secondary inlet. For example, as described above with respect to Figure 6B As discussed, in some embodiments, the secondary inlet can be positioned about the hub 831 or shaft 832. The rotation of the blade 820 can force air into the blade inlet 851, through the blade passage 850, and to the blade outlet 852, as shown by the dashed arrows. The blade outlet can be located in the hub 831 as shown, or can be formed elsewhere, such as at the root of the blade 820 near the hub 831. Alternatively, one or more blade outlets 852 can be arranged, for example, in the middle of the blade 820 to align with another inlet (e.g., Figures 6A-6E 640) is aligned with the entrance.

[0108] Figure 9A-9B 1 and 2 show further example auxiliary features on a lift propeller in a portion of a VTOL aircraft 900 consistent with an embodiment of the present disclosure. The VTOL aircraft 900 may be, for example, similar to Figures 1-8 Any of the VTOL aircraft 100 , 400 , 500 , 600 , 700 or 800 . Figure 9A-9B Zhongyu Figures 1-8 Elements similar to the elements in can be marked with corresponding numbers using 9 as the leading digit. For example, in some embodiments, Figure 9A The blade 920 may be similar to Figure 4A The blades are 420.

[0109] Figure 9A A plurality of integrated cooling blades 953 are shown consistent with embodiments of the present disclosure. The cooling blades 953 may be located, for example, on the rotor or hub 932 below the lift propeller blades 920. The cooling blades may direct the cooling air flow through the secondary inlet to, for example, the stator of the motor assembly. For example, as described above with respect to Figure 6BAs discussed, in some embodiments, the secondary inlet can be positioned around the hub 831 or shaft 832. The flow rate of the cooling air can be proportional to the rotational speed of the lift propeller, and therefore proportional to the rate of heat generation in the lift propeller motor assembly. This creates a cooling system design that passively increases the flow rate as needed when the lift propeller generates more heat. The cooling blade configuration can be added without the need for additional failure-prone components (such as dedicated motors, wiring, or controllers).

[0110] Figure 9B Another configuration of multiple integrated cooling paddles 953 is shown consistent with an embodiment of the present disclosure. Figure 9B , cooling paddles 953 may be arranged about shaft 931 and surrounded by a fan shroud 954. The fan shroud 954 may be configured to direct cooling air flow through the cooling paddles 953 to improve air flow to the motor assembly.

[0111] Some embodiments of the present disclosure (e.g. Figures 6A-7B ) has been described with respect to the inlet being located on the fairing. However, the embodiments of the present disclosure are not limited thereto. Figure 5A-Figure 5N As discussed in , for the reasons stated above, embodiments of the present disclosure may alternatively position the inlet or outlet on a boom rather than a fairing. Similarly, elements shown as fairings in some figures may alternatively be formed as part of a boom.

[0112] The embodiments may be further described using the following terms:

[0113] Clause Set A:

[0114] 1. A lifting device for a vertical take-off and landing (VTOL) aircraft, comprising:

[0115] lift propeller;

[0116] a motor assembly coupled to the lift propeller;

[0117] a boom supporting the motor assembly;

[0118] a fairing coupled to the boom and surrounding the motor assembly;

[0119] an air inlet located on a top side of the fairing, the air inlet being configured to receive downwash from the lift propeller during a lift phase of the VTOL aircraft;

[0120] a cooling path configured to direct the downwash flow to the motor assembly; and

[0121] An air outlet is configured to exhaust the downwash flow from the cooling path.

[0122] 2. The lifting apparatus of clause A1 , wherein the center of the air inlet is aligned with the longitudinal axis of the boom.

[0123] 3. A lifting apparatus as described in clause A1 or A2, wherein the center of the air inlet is offset from the longitudinal axis of the boom.

[0124] 4. A lift apparatus according to clause A3, wherein the offset of the air inlet corresponds to an area of ​​highest downwash pressure from the lift propeller in a direction perpendicular to the longitudinal axis of the boom.

[0125] 5. A lifting device according to any of clauses A1 to A4, wherein the air inlet comprises a plurality of air inlets.

[0126] 6. A lifting device according to clause A5, wherein:

[0127] the plurality of air inlets being offset from one another in the direction of the longitudinal axis of the boom;

[0128] The plurality of air inlets are offset from one another in a direction perpendicular to the longitudinal axis of the boom; and

[0129] For each of the plurality of air inlets, the offset in the direction perpendicular to the longitudinal axis of the boom corresponds to an area having a highest downwash pressure from the lift propeller in the vertical direction.

[0130] 7. A lifting device according to any of clauses A1 to A6, wherein, in a cross-section of the fairing, the width of the air inlet is greater than 50% of the width of the fairing.

[0131] 8. The lifting apparatus of clause A7, wherein, in a cross-section of the fairing, the width of the air inlet is greater than 75% of the width of the fairing.

[0132] 9. A lifting device according to any one of clauses A1 to A8, further comprising:

[0133] a second lift propeller;

[0134] a second motor assembly coupled to the second lifting propeller;

[0135] a second boom supporting the second motor assembly;

[0136] a second fairing coupled to the second boom and surrounding the second motor assembly;

[0137] a second air inlet located on a top side of the second fairing, the second air inlet being configured to receive a second downwash of the second lift propeller during the lift phase of the VTOL aircraft;

[0138] a second cooling path configured to direct the second downwash flow to the second motor assembly; and

[0139] A second air outlet is configured to discharge the second downwash flow from the second cooling path.

[0140] 10. The lifting device of clause A9, wherein:

[0141] The motor assembly is configured to rotate the lift propeller in a first rotational direction;

[0142] the second motor assembly being configured to rotate the second propeller in a second rotational direction opposite to the first rotational direction;

[0143] The center of the air inlet is offset from the longitudinal axis of the boom in a first offset direction; and

[0144] A center of the second air inlet is offset from a longitudinal axis of the second boom in a second offset direction opposite the first offset direction.

[0145] 11. A lifting device according to any of clauses A1 to A10, wherein the air outlet is located in the fairing.

[0146] 12. A lifting device according to any of clauses A1 to A11, wherein the air outlet is located on an underside of the fairing.

[0147] 13. The lifting apparatus of clause A12, wherein the air outlet is located below a heat exchanger of the motor assembly.

[0148] 14. A lifting device according to any of clauses A1 to A12, wherein the air outlet is located on a top side of the fairing.

[0149] 15. The lift device of clause A14, further comprising a second air outlet located in an underside of the fairing.

[0150] 16. A lift device as described in clause A14 or A15, wherein the air outlet surrounds the axis of the lift propeller.

[0151] 17. The lifting device of clause A16, wherein the air outlet comprises an elliptical shape.

[0152] 18. A lifting device according to any of clauses A14 to A17, wherein the air outlet is located below a hub of the lifting propeller.

[0153] 19. The lift apparatus of clause A18, wherein a section of the outer boundary of the air outlet is located below a hub of the lift propeller.

[0154] 20. A lifting device according to any one of clauses A1 to A18, further comprising:

[0155] a first downwash flow path directed to an upper portion of the motor assembly; and

[0156] A second downwash flow path is directed to a lower portion of the motor assembly.

[0157] 21. The lifting device of clause A20, wherein:

[0158] The air inlet includes a first sub-air inlet and a second sub-air inlet;

[0159] The first sub-air inlet is configured to direct a first portion of the downwash flow to the first downwash flow path; and

[0160] The second sub-air inlet is configured to guide a second portion of the downwash flow to the second downwash flow path.

[0161] 22. The lift apparatus of clause A20 or A21, further comprising a baffle configured to bifurcate the downwash flow into the first downwash flow path and the second downwash flow path.

[0162] 23. A lifting device according to any of clauses A1 to A22, wherein:

[0163] The motor assembly includes a hybrid cooling motor assembly having a first motor assembly portion and a second motor assembly portion;

[0164] the first motor assembly portion being configured to be directly air cooled by a first portion of the downwash flow in the first downwash flow path;

[0165] The second motor assembly portion is configured for indirect air cooling via a fluid heat exchange medium in a second portion of the downwash in a second downwash flow path.

[0166] 24. The lift apparatus of any of clauses A1 to A23, further comprising a manifold configured to distribute the downwash flow around the motor assembly.

[0167] 25. A lifting apparatus according to any of clauses A1 to A24, further comprising a door configured to:

[0168] opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash, and

[0169] Closes to cover the air inlet during the cruise phase of the VTOL aircraft.

[0170] 26. The lift apparatus of clause A25, further comprising a control actuator configured to actuate the door.

[0171] 27. A lifting apparatus as described in clause A25 or A26, further comprising a biasing mechanism configured to bias the door to a closed position.

[0172] 28. The lift apparatus of clause A27, wherein the biasing force of the biasing mechanism is configured to be higher than an opposing force from the air during the cruise phase of the VTOL aircraft and lower than an opposing force from the air during the lift phase of the VTOL aircraft.

[0173] 29. A lifting device as described in any of clauses A25 to A28, wherein the door is configured to open by a vortex component of the downwash flow.

[0174] 30. A lifting device as described in any of clauses A25 to A29, wherein the door comprises a hinge in the fairing.

[0175] 31. A lifting apparatus as described in any of clauses A1 to A30, wherein the motor assembly comprises a motor, a gearbox and an inverter.

[0176] 32. A lifting device according to clause A31, wherein:

[0177] The motor and the gearbox share a common longitudinal axis; and

[0178] The inverter axis is offset from the longitudinal axis of the motor and the gearbox.

[0179] 33. A lifting device according to clause A31 or A32, wherein:

[0180] The motor assembly includes redundant components.

[0181] 34. The lift apparatus of clause A33, wherein the redundant components comprise at least one of redundant stators of the motor and redundant inverter stages of the inverter.

[0182] 35. A vertical take-off and landing (VTOL) aircraft comprising a lift device according to any of clauses A1 to A35.

[0183] Clause Set B:

[0184] 1. A lifting device for a vertical take-off and landing (VTOL) aircraft, comprising:

[0185] lift propeller;

[0186] a motor assembly coupled to the lift propeller, the motor assembly being located within the housing;

[0187] a heat exchanger located external to the housing, the heat exchanger thermally coupled to the motor assembly via a coolant flow path;

[0188] boom;

[0189] fairing;

[0190] an air inlet located on a top side of the boom or the fairing, the air inlet being configured to receive downwash from the lift propeller during a lift phase of the VTOL aircraft;

[0191] a cooling path configured to direct the downwash flow to the heat exchanger; and

[0192] An air outlet is configured to discharge the downwash flow from the heat exchanger.

[0193] 2. A lifting apparatus according to clause B1, wherein the centre of the air inlet is aligned with the longitudinal axis of the boom.

[0194] 3. A lifting apparatus as described in clause B1 or B2, wherein the center of the air inlet is offset from the longitudinal axis of the boom.

[0195] 4. The lift apparatus of clause B3, wherein the air inlet is offset relative to the air inlet to a side of the longitudinal axis having the highest downwash pressure from the lift propeller.

[0196] 5. A lifting device according to any of clauses B1 to B4, wherein the air inlet comprises a plurality of air inlets.

[0197] 6. A lifting device according to clause B5, wherein:

[0198] The plurality of air inlets are located at different radial distances from the hub of the lift propeller;

[0199] The plurality of air inlets are offset from one another in a direction perpendicular to a longitudinal axis of the boom; and

[0200] For each of the plurality of air inlets, the offset in the direction perpendicular to the longitudinal axis of the boom corresponds to a side of the longitudinal axis having a highest downwash pressure from the lift propeller at the radial distance.

[0201] 7. A lifting apparatus according to any of clauses B1 to B6, wherein, in a cross section of the boom, the width of the air inlet is greater than 50% of the width of the boom.

[0202] 8. A lifting apparatus according to clause B7, wherein, in a cross section of the boom, the width of the air inlet is greater than 75% of the width of the boom.

[0203] 9. A lifting device according to any one of clauses B1 to B8, further comprising:

[0204] a second lift propeller;

[0205] a second motor assembly coupled to the second lift propeller, the second motor assembly being located within the second housing;

[0206] a second heat exchanger located outside the second housing, the second heat exchanger thermally coupled to the motor assembly via a second coolant flow path;

[0207] Second boom;

[0208] Second fairing;

[0209] a second air inlet located on a top side of the second boom or the second fairing, the second air inlet being configured to receive a second downwash of the second lift propeller during the lift phase of the VTOL aircraft;

[0210] a second cooling path configured to direct the second downwash flow to the second heat exchanger; and

[0211] A second air outlet is configured to discharge the second downwash flow from the second heat exchanger.

[0212] 10. A lifting device according to clause B9, wherein:

[0213] The motor assembly is configured to rotate the lift propeller in a first rotational direction;

[0214] the second motor assembly being configured to rotate the second propeller in a second rotational direction opposite to the first rotational direction;

[0215] The center of the air inlet is offset from the longitudinal axis of the boom in a first offset direction; and

[0216] A center of the second air inlet is offset from a longitudinal axis of the second boom in a second offset direction opposite the first offset direction.

[0217] 11. A lifting device as described in any of clauses B1 to B10, wherein the air outlet is located in the boom.

[0218] 12. A lifting device according to any of clauses B1 to B11, wherein the air outlet is located on an underside of the fairing.

[0219] 13. A lifting apparatus according to clause B12, wherein the air outlet is located below the heat exchanger.

[0220] 14. A lifting device according to any of clauses B1 to B13, wherein the air outlet is located on a top side of the fairing.

[0221] 15. The lift device of clause B14, further comprising a second air outlet located in an underside of the fairing.

[0222] 16. A lift device according to clause B14 or B15, wherein the air outlet surrounds the axis of the lift propeller.

[0223] 17. The lifting device of clause B16, wherein the air outlet comprises an elliptical shape.

[0224] 18. A lifting device according to any of clauses B14 to B17, wherein the air outlet is located below the hub of the lifting propeller.

[0225] 19. The lift apparatus of clause B18, wherein a section of the outer boundary of the air outlet is located below a hub of the lift propeller.

[0226] 20. A lifting device according to any one of clauses B1 to B19, further comprising:

[0227] a first downwash flow path directed to an upper portion of the motor assembly; and

[0228] A second downwash flow path is directed to a lower portion of the motor assembly.

[0229] 21. A lifting device according to clause B20, wherein:

[0230] The air inlet includes a first sub-air inlet and a second sub-air inlet;

[0231] The first sub-air inlet is configured to direct a first portion of the downwash flow to the first downwash flow path; and

[0232] The second sub-air inlet is configured to guide a second portion of the downwash flow to the second downwash flow path.

[0233] 22. The lift apparatus of clause B20 or B21, further comprising a baffle configured to bifurcate the downwash flow into the first downwash flow path and the second downwash flow path.

[0234] 23. A lifting device according to any of clauses B1 to B22, wherein:

[0235] The motor assembly includes a hybrid cooling motor assembly having a first motor assembly portion and a second motor assembly portion;

[0236] the first motor assembly portion being configured to be directly air cooled by a first portion of the downwash flow in a first downwash flow path;

[0237] The second motor assembly portion is configured for indirect air cooling via a fluid heat exchange medium in a second portion of the downwash in a second downwash flow path.

[0238] 24. A lift apparatus according to any of clauses B1 to B23, further comprising a manifold configured to distribute the downwash flow around the motor assembly.

[0239] 25. A lifting apparatus according to any of clauses B1 to B24, further comprising a door configured to:

[0240] opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash, and

[0241] Closes to cover the air inlet during the cruise phase of the VTOL aircraft.

[0242] 26. The lift apparatus of clause B25, further comprising a control actuator configured to actuate the door.

[0243] 27. A lifting apparatus according to clause B25 or B26, further comprising a biasing mechanism configured to bias the door to a closed position.

[0244] 28. The lift apparatus of clause B27, wherein the biasing force of the biasing mechanism is configured to be higher than an opposing force from the air during the cruise phase of the VTOL aircraft and lower than an opposing force from the air during the lift phase of the VTOL aircraft.

[0245] 29. A lifting device according to any of clauses B25 to B28, wherein the door is configured to open by a vortex component of the downwash flow.

[0246] 30. A lifting device according to any of clauses B25 to B29, wherein the door comprises a hinge in the fairing.

[0247] 31. A lift apparatus as described in any of clauses B1 to B30, wherein the coolant flow path comprises a lubrication flow path, and the coolant is configured to lubricate components of the motor assembly.

[0248] 32. A lifting apparatus as described in any of clauses B1 to B31 wherein the motor assembly comprises a motor, a gearbox and an inverter.

[0249] 33. A lifting device according to clause B32, wherein:

[0250] The motor and the gearbox share a common longitudinal axis; and

[0251] The inverter axis is offset from the longitudinal axis of the motor and the gearbox.

[0252] 34. A lifting device according to clause B32 or B33, wherein:

[0253] The motor assembly includes redundant components.

[0254] 35. The lift apparatus of clause B34, wherein the redundant components comprise at least one of redundant stators of the motor and redundant inverter stages of the inverter.

[0255] 36. A vertical take-off and landing (VTOL) aircraft comprising a lift device according to any one of clauses B1 to B35.

[0256] Clause Set C:

[0257] 1. A lifting device for a vertical take-off and landing (VTOL) aircraft, comprising:

[0258] lift propeller;

[0259] a motor assembly coupled to the lift propeller, the motor assembly being located within the housing;

[0260] a heat exchanger located external to the housing, the heat exchanger thermally coupled to the motor assembly via a coolant flow path;

[0261] boom;

[0262] fairing;

[0263] an air inlet located on a top side of the boom or the fairing, the air inlet being configured to receive downwash from the lift propeller during a lift phase of the VTOL aircraft;

[0264] a first cooling path configured to direct a first portion of the downwash flow to cool a portion of the housing surrounding the motor assembly;

[0265] a second cooling path configured to direct a second portion of the downwash flow to cool the heat exchanger; and

[0266] An air outlet is configured to discharge the downwash flow from the first cooling path or the second cooling path.

[0267] 2. A lifting apparatus according to clause C1, wherein the centre of the air inlet is aligned with the longitudinal axis of the boom.

[0268] 3. A lifting apparatus according to clause C1 or C2, wherein the centre of the air inlet is offset from the longitudinal axis of the boom.

[0269] 4. The lift apparatus of clause C3, wherein the air inlet is offset relative to the air inlet to a side of the longitudinal axis having the highest downwash pressure from the lift propeller.

[0270] 5. A lifting device according to any of clauses C1 to C4, wherein the air inlet comprises a plurality of air inlets.

[0271] 6. A lifting device according to clause C5, wherein:

[0272] The plurality of air inlets are located at different radial distances from the hub of the lift propeller;

[0273] The plurality of air inlets are offset from one another in a direction perpendicular to a longitudinal axis of the boom; and

[0274] For each of the plurality of air inlets, the offset in the direction perpendicular to the longitudinal axis of the boom corresponds to a side of the longitudinal axis having a highest downwash pressure from the lift propeller at the radial distance.

[0275] 7. A lifting device according to any of clauses C1 to C6, wherein, in a cross section of the boom, the width of the air inlet is greater than 50% of the width of the boom.

[0276] 8. A lifting apparatus according to clause C7, wherein, in a cross-section of the boom, the width of the air inlet is greater than 75% of the width of the boom.

[0277] 9. A lifting device according to any of clauses C1 to C8, further comprising:

[0278] a second lift propeller;

[0279] a second motor assembly coupled to the second lift propeller, the second motor assembly being located within the second housing;

[0280] a second heat exchanger located outside the second housing, the second heat exchanger thermally coupled to the motor assembly via a second coolant flow path;

[0281] Second boom;

[0282] Second fairing;

[0283] a second air inlet located on a top side of the second boom or the second fairing, the second air inlet being configured to receive a second downwash of the second lift propeller during the lift phase of the VTOL aircraft;

[0284] a third cooling path configured to direct a first portion of the second downwash flow to cool an outer upper portion of the second motor assembly;

[0285] a fourth cooling path configured to direct a second portion of the second downwash flow to cool the heat exchanger; and

[0286] as well as

[0287] A second air outlet is configured to discharge the second downwash flow from the third cooling path or the fourth cooling path.

[0288] 10. A lifting device according to clause C9, wherein:

[0289] The motor assembly is configured to rotate the lift propeller in a first rotational direction;

[0290] the second motor assembly being configured to rotate the second propeller in a second rotational direction opposite to the first rotational direction;

[0291] The center of the air inlet is offset from the longitudinal axis of the boom in a first offset direction; and

[0292] A center of the second air inlet is offset from a longitudinal axis of the second boom in a second offset direction opposite the first offset direction.

[0293] 11. A lifting device according to any of clauses C1 to C10, wherein the air outlet is located in the boom.

[0294] 12. A lifting device according to any of clauses C1 to C11, wherein the air outlet is located on an underside of the fairing.

[0295] 13. A lifting apparatus according to clause C12, wherein the air outlet is located below the heat exchanger.

[0296] 14. A lifting device according to any of clauses C1 to C13, wherein the air outlet is located on a top side of the fairing.

[0297] 15. The lift device of clause C14, further comprising a second air outlet located in an underside of the fairing.

[0298] 16. A lifting device according to clause C14 or C15, wherein the air outlet surrounds the axis of the lifting propeller.

[0299] 17. The lifting device of clause C16, wherein the air outlet comprises an elliptical shape.

[0300] 18. A lifting device according to any of clauses C14 to C17, wherein the air outlet is located below a hub of the lifting propeller.

[0301] 19. A lift apparatus according to clause C18, wherein a section of the outer boundary of the air outlet is located below the hub of the lift propeller.

[0302] 20. A lifting device according to any of clauses C1 to C19, wherein:

[0303] The air inlet includes a first air inlet and a second air inlet;

[0304] the first air inlet being configured to direct the first portion of the downwash flow to the first cooling path; and

[0305] The second air inlet is configured to direct the second portion of the downwash flow to the second cooling path.

[0306] 21. The lift apparatus of clause C20, further comprising a baffle configured to bifurcate the downwash flow into the first cooling path and the second cooling path.

[0307] 22. The lift apparatus of any of clauses C1 to C21, further comprising a manifold configured to distribute the downwash flow around the motor assembly.

[0308] 23. A lifting apparatus according to any of clauses C1 to C22, further comprising a door configured to:

[0309] opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash, and

[0310] Closes to cover the air inlet during the cruise phase of the VTOL aircraft.

[0311] 24. The lifting apparatus of clause C23, further comprising a control actuator configured to actuate the door.

[0312] 25. The lifting apparatus of clause C23 or C24, further comprising a biasing mechanism configured to bias the door to a closed position.

[0313] 26. The lift apparatus of clause C25, wherein the biasing force of the biasing mechanism is configured to be higher than an opposing force from the air during the cruise phase of the VTOL aircraft and lower than an opposing force from the air during the lift phase of the VTOL aircraft.

[0314] 27. A lifting device according to any of clauses C23 to C26, wherein the door is configured to open by a vortex component of the downwash flow.

[0315] 28. A lifting device according to any of clauses C23 to C27, wherein the door comprises a hinge in the fairing.

[0316] 29. A lift apparatus as described in any of clauses C1 to C28, wherein the coolant flow path comprises a lubrication flow path, and the coolant is configured to lubricate components of the motor assembly.

[0317] 30. A lifting apparatus as described in any of clauses C1 to C29, wherein the motor assembly comprises a motor, a gearbox and an inverter.

[0318] 31. A lifting device according to clause C30, wherein:

[0319] The motor and the gearbox share a common longitudinal axis; and

[0320] The inverter axis is offset from the longitudinal axis of the motor and the gearbox.

[0321] 32. A lifting device according to clause C30 or C31, wherein:

[0322] The motor assembly includes redundant components.

[0323] 33. The lift apparatus of clause C32, wherein the redundant component comprises at least one of a redundant stator of the motor and a redundant inverter stage of the inverter.

[0324] 34. A vertical take-off and landing (VTOL) aircraft comprising a lift device according to any of clauses C1 to C33.

[0325] Clause Set D:

[0326] 1. A device for a vertical take-off and landing (VTOL) aircraft, the device comprising:

[0327] propeller;

[0328] a support structure for the VTOL aircraft;

[0329] an electric engine mounted to the support structure and configured to rotate the propeller, the electric engine being located within the housing;

[0330] a first heat transfer element thermally coupled to the electric power engine, wherein at least a portion of the first heat transfer element is located outside of the housing;

[0331] an air inlet located on an upper side of the support structure, wherein the air inlet is configured to receive downwash from the propeller during a lift phase;

[0332] a first cooling path configured to direct a first portion of the downwash flow from the air inlet to the first heat transfer element; and

[0333] A first air outlet is configured to exhaust the first portion of the downwash flow from the first heat transfer element.

[0334] 2. The apparatus of clause D1, wherein the first heat transfer element comprises a heat exchanger.

[0335] 3. The apparatus of clause D2, further comprising:

[0336] An oil flow path is provided, wherein the heat exchanger is thermally coupled to the electric engine through the oil flow path.

[0337] 4. An apparatus as described in clause D3, wherein:

[0338] The electric engine includes a motor; and

[0339] The housing includes a motor housing enclosing the motor,

[0340] The oil flow path is configured to circulate oil within the motor housing.

[0341] 5. The apparatus of clause D4, wherein:

[0342] The electric power engine further includes an inverter; and

[0343] The housing includes an inverter housing enclosing the inverter and a partition plate between the motor housing and the inverter housing.

[0344] Wherein the separator plate is configured to thermally couple the inverter to the oil flow path.

[0345] 6. An apparatus as described in clause D4 or D5, wherein:

[0346] The electric engine includes a gearbox; and

[0347] The housing comprises a gearbox housing enclosing the gearbox,

[0348] The oil flow path is configured to circulate oil within the gearbox housing.

[0349] 7. The apparatus of any of clauses D1 to D6, further comprising:

[0350] a second heat transfer element thermally coupled to the electric power engine, wherein at least a portion of the second heat transfer element is located external to the housing; and

[0351] A second cooling path is configured to direct a second portion of the downwash flow from the air inlet to the second heat transfer element.

[0352] 8. The apparatus of clause D7, further comprising a baffle configured to split the downwash flow from the air inlet into the first cooling path and the second cooling path.

[0353] 9. An apparatus as described in clause D7 or D8, wherein:

[0354] The inlet includes a first air inlet and a second air inlet;

[0355] the first cooling path being configured to receive the first portion of the downwash flow from the first air inlet; and

[0356] The second cooling path is configured to receive the second portion of the downwash flow from the second air inlet.

[0357] 10. Apparatus according to any of clauses D7 to D9, wherein the first air outlet is configured to discharge the second portion of the downwash flow from the second heat transfer element.

[0358] 11. The apparatus of any of clauses D7 to D10, further comprising:

[0359] A second air outlet is provided, wherein the second air outlet is configured to discharge the second portion of the downwash flow from the second heat transfer element.

[0360] 12. Apparatus according to clause 11, wherein the second air outlet is located on an upper side of the support structure.

[0361] 13. The apparatus of any of clauses D7 to D12, further comprising:

[0362] Oil flow path, where:

[0363] The power engine includes a hybrid cooled power engine having a first portion and a second portion;

[0364] the first heat transfer element comprises a heat exchanger thermally coupled to the first portion of the electric engine via the oil flow path; and

[0365] The second heat transfer element includes air-cooled fins thermally coupled to the second portion of the power engine.

[0366] 14. The apparatus of clause D13, wherein:

[0367] One of the first portion of the power engine or the second portion of the power engine includes a motor; and

[0368] The other of the first portion of the power engine or the second portion of the power engine includes an inverter.

[0369] 15. The apparatus of any of clauses D1 to D14, further comprising:

[0370] a second heat transfer element thermally coupled to the electric power engine, wherein at least a portion of the second heat transfer element is located outside of the housing,

[0371] Wherein the first cooling path is configured to direct the downwash flow from the first heat transfer element to the second heat transfer element.

[0372] 16. The apparatus of any of clauses D1 to D15, further comprising:

[0373] A door, the door being configured to:

[0374] opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash, and

[0375] Closes to cover the air inlet during the cruise phase of the VTOL aircraft.

[0376] 17. The apparatus of clause 16, further comprising a biasing mechanism configured to bias the door to a closed position, wherein a biasing force of the biasing mechanism is configured to be higher than a first opposing force from the air during the cruise phase of the VTOL aircraft and lower than a second opposing force from the air during the lift phase of the VTOL aircraft.

[0377] 18. Apparatus according to clause D16 or D17, wherein the door is configured to open by a vortex component of the downwash flow.

[0378] 19. Apparatus according to any of clauses D16 to D18, wherein the door is configured to be forced open inwardly into the support structure by the downwash flow.

[0379] 20. Apparatus according to any of clauses D16 to D19, wherein:

[0380] In a cross-sectional direction of the support structure perpendicular to a longitudinal axis of the support structure, the width of the door is at least 75% of the width of the support structure.

[0381] 21. Apparatus according to clause 20, wherein the length of the door in the direction of the longitudinal axis is greater than the width of the door.

[0382] 22. The propeller apparatus of any one of clauses D1 to D21, further comprising:

[0383] A boom, wherein the support structure comprises one of the boom or a fairing coupled to the boom.

[0384] 23. A method of operating a vertical take-off and landing (VTOL) aircraft, comprising:

[0385] rotating a propeller in a lift configuration of the VTOL aircraft by an electric engine located within a housing and mounted to a support structure of the VTOL aircraft;

[0386] directing downwash from the propeller through an air inlet located at an upper side of the support structure,

[0387] receiving a portion of the downwash flow in a cooling path via the air inlet;

[0388] directing the portion of the downwash flow via the cooling path to a heat transfer element, at least a portion of which is external to the housing and thermally coupled to the power engine; and

[0389] The portion of the downwash flow is exhausted from the heat transfer element via an air outlet.

[0390] 24. An apparatus for a vertical take-off and landing (VTOL) aircraft, the apparatus comprising:

[0391] propeller;

[0392] a support structure for the VTOL aircraft;

[0393] an electric engine mounted to the support structure and configured to rotate the propeller;

[0394] an air inlet located on an upper side of the support structure, wherein the air inlet is configured to receive downwash from the propeller during a lift phase;

[0395] a first cooling path configured to direct a first portion of the downwash flow from the air inlet to a first portion of the power engine; and

[0396] A second cooling path is configured to direct a second portion of the downwash flow from the air inlet to a second portion of the power engine.

[0397] 25. The apparatus of clause D24, further comprising:

[0398] a first heat transfer element thermally coupled to the first portion of the power engine; and

[0399] A second heat transfer element is thermally coupled to the second portion of the power engine.

[0400] 26. The apparatus of clause D25, further comprising:

[0401] Oil flow path, where:

[0402] The power engine includes a hybrid cooled power engine having a first portion and a second portion;

[0403] the first heat transfer element comprises a heat exchanger thermally coupled to the first portion of the electric engine via the oil flow path; and

[0404] The second heat transfer element includes air-cooled fins thermally coupled to the second portion of the power engine.

[0405] 27. The apparatus of any of clauses D24 to D26, further comprising:

[0406] A housing surrounds the electric power engine, wherein at least a portion of the first heat transfer element and at least a portion of the second heat transfer element are located outside of the housing.

[0407] 28. Apparatus according to any of clauses D24 to D27, wherein:

[0408] One of the first portion of the power engine or the second portion of the power engine includes a motor; and

[0409] The other of the first portion of the power engine or the second portion of the power engine includes an inverter.

[0410] 29. The apparatus of any of clauses D24 to D28, further comprising:

[0411] A door, wherein the door is configured as follows:

[0412] opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash; and

[0413] closing to cover the air inlet during a cruise phase of the VTOL aircraft;

[0414] wherein the door is configured to open by a vortex component of the downwash flow.

[0415] 30. The apparatus of any of clauses D24 to D29, further comprising:

[0416] A boom, wherein the support structure comprises one of the boom or a fairing coupled to the boom.

[0417] The foregoing description has been presented for illustrative purposes. This description is not exhaustive and does not limit the invention to the precise forms or embodiments disclosed. Modifications and adaptations of the invention will be apparent to those skilled in the art through consideration of the specification and practice of the disclosed embodiments of the invention disclosed herein.

Claims

1. A propeller device for a vertical take-off and landing (VTOL) aircraft, comprising: propeller; a support structure for the VTOL aircraft; an electric engine mounted to the support structure and configured to rotate the propeller, the electric engine being located within the housing; a first heat transfer element thermally coupled to the electric power engine, wherein at least a portion of the first heat transfer element is located outside of the housing; an air inlet located on an upper side of the support structure, wherein the air inlet is configured to receive downwash from the propeller during a lift phase; a first cooling path configured to direct a first portion of the downwash flow to the first heat transfer element; a second cooling path configured to direct a second portion of the downwash flow to a second heat transfer element thermally coupled to the power engine; a first air outlet configured to exhaust the first portion of the downwash flow from the first heat transfer element; as well as A second air outlet is configured to discharge the second portion of the downwash flow from the second heat transfer element.

2. The propeller apparatus of claim 1 , wherein the first heat transfer element comprises a heat exchanger, and the propeller apparatus further comprises: An oil flow path is provided, wherein the heat exchanger is thermally coupled to the electric engine through the oil flow path.

3. The propeller device according to claim 2, wherein: The electric engine includes a motor; and The housing includes a motor housing enclosing the motor, The oil flow path is configured to circulate oil within the motor housing.

4. The propeller device according to claim 3, wherein: The electric power engine further includes an inverter; and The housing includes an inverter housing enclosing the inverter and a partition plate between the motor housing and the inverter housing. Wherein the separator plate is configured to thermally couple the inverter to the oil flow path.

5. The propeller device according to claim 3, wherein: The electric engine includes a gearbox; and The housing comprises a gearbox housing enclosing a gearbox, The oil flow path is configured to circulate oil within the gearbox housing.

6. The propeller device according to claim 1, wherein: The air inlet includes a first air inlet and a second air inlet; the first cooling path being configured to receive the first portion of the downwash flow from the first air inlet; and The second cooling path is configured to receive the second portion of the downwash flow from the second air inlet. The propeller apparatus according to claim 1 , wherein the second air outlet is located on an upper side of the support structure.

8. The propeller device according to claim 1, further comprising: Oil flow path, where: The power engine includes a hybrid cooled power engine having a first portion and a second portion; the first heat transfer element comprises a heat exchanger thermally coupled to the first portion of the electric engine via the oil flow path; and The second heat transfer element includes air-cooled fins thermally coupled to the second portion of the power engine.

9. The propeller device according to claim 8, wherein: One of the first portion of the power engine and the second portion of the power engine includes a motor; and The other of the first portion of the power engine and the second portion of the power engine includes an inverter.

10. The propeller device according to any one of claims 1 to 9, further comprising: A door, the door being configured to: opening during the lift phase of the VTOL aircraft to expose the air inlet to the downwash, and Closes to cover the air inlet during the cruise phase of the VTOL aircraft.

11. The propeller device according to claim 10, further comprising: A biasing mechanism is configured to bias the door to a closed position, wherein a biasing force of the biasing mechanism is configured to be higher than a first opposing force from air during the cruise phase of the VTOL aircraft and lower than a second opposing force from air during the lift phase of the VTOL aircraft.

12. The propeller apparatus of claim 10, wherein the door is configured to open by a vortex component of the downwash flow.

13. The propeller apparatus of claim 10, wherein the door is configured to be forced open inwardly into the support structure by the downwash flow.

14. The propeller device according to claim 10, wherein: In a cross-sectional direction of the support structure perpendicular to a longitudinal axis of the support structure, the width of the door is at least 75% of the width of the support structure. 15 . The propeller apparatus according to claim 10 , wherein a length of the door in the direction of the longitudinal axis is greater than a width of the door.

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