Systems and methods for off-axis cooling fan for a propeller

Abstract

A cooling system for an aircraft comprises: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a rotor coupled to the drive shaft; a stator adjacent to the rotor; and a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis. Rotation of the rotor with respect to the stator generates an electric current sent to the fan through at least one wire to cause the fan to rotate around the second axis. The fan is configured to drive an airflow from the inlet to the outlet.

Description

Agent Reference: 16498-0014-00304SYSTEMS AND METHODS FOR OFF-AXIS COOLING FAN FOR A PROPELLERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 686,586, filed on August 23, 2024, entitled “Systems And Methods For Off-Axis Cooling Fan For A Propeller,” and of U.S. Provisional Patent Application No. 63 / 861,903, filed on August 11, 2025, entitled “Propeller Pitch Control Systems And Methods”, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] This disclosure relates generally to the field of powered aerial vehicles. More particularly, and without limitation, the present disclosure relates to innovations in aircraft that use electrical propulsion systems. Certain aspects of the present disclosure generally relate to operating a cooling fan off-axis from a propeller motor. Other aspects of the present disclosure generally relate to improvements in operating an off-axis cooling fan relative to a motor axis that may be used in other types of vehicles but provide particular advantages in aerial vehicles.SUMMARY

[0003] Embodiments of the present disclosure describe systems and methods for a cooling system for an aircraft.

[0004] In some embodiments, a cooling system comprises: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a rotor coupled to the drive shaft; a stator adjacent to the rotor; and a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis. Rotation of the rotor with respect to the stator is configured to generate an electric current sent to the fan through at least one wire to cause the fan to rotate around the second axis. The fan is configured to drive an airflow from the inlet to the outlet.

[0005] The outlet may be located below the heat exchanger.

[0006] The first axis and the second axis may be parallel.

[0007] The first axis and the second axis may not be parallel.

[0008] The rotor and the stator of the cooling system may form a brushless DC motor. The brushless DC motor may be configured to use a number of poles to control a rotation speed of the fan. In the cooling system, the electric current may pass through at least one resistor before reaching the fan.Agent Reference: 16498-0014-00304

[0009] The at least one resistor may comprise a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft. The at least one resistor may comprise a variable resistor configured to alter the electric current reaching the fan, causing the rotation speed of the fan to be different from or equal to the rotation speed of the drive shaft.

[0010] In the cooling system, the heat exchanger may be affixed to a housing of the engine.

[0011] In some embodiments embodiment, a cooling system comprises: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; and a fan belt coupled to the drive shaft and the fan. The fan belt causes the fan to rotate around the second axis when the drive shaft rotates around the first axis. The fan is configured to drive an airflow from the inlet to the outlet.

[0012] The outlet may be located below the heat exchanger.

[0013] The first axis and the second axis may be parallel.

[0014] The first axis and the second axis may not be parallel.

[0015] A rotation speed of the fan may be equal to a rotation speed of the drive shaft.

[0016] A rotation speed of the fan may be different from a rotation speed of the drive shaft.

[0017] The cooling system may comprise a second fan belt coupled to a pulley and configured to change a rotation speed of the fan relative to a rotation speed of the drive shaft.

[0018] The fan belt may be coupled to a gearbox to change a rotation speed of the fan relative to a rotation speed of the drive shaft.

[0019] The heat exchanger of the cooling system may be affixed to a housing of the engine.

[0020] In some embodiments, a cooling system comprises: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; a first motor configured to drive a component of the aircraft other than the fan in a first mode of operation; and a second motor configured to drive the fan. The first motor is configured to power the second motor in a second mode of operation, and the fan is configured to drive an airflow from the inlet to the outlet.Agent Reference: 16498-0014-00304

[0021] The component of the aircraft other than the fan may be a pitch control apparatus.

[0022] The first motor may comprise a rotor and a stator operably disposed in a frame, wherein the rotor and stator are configured to produce torque about a shared central axis.

[0023] The rotor may comprise permanent magnets circumferentially positioned to enable electromagnetic induction. Upon energization of the stator, electromagnetic fields may interact with the rotor to induce rotational motion of the rotor. The rotor may be mechanically linked to a pitch control rod, and configured to convert electromagnetic excitation of the rotor and stator into mechanical torque output. The first motor may be configured to engage the pitch control rod.

[0024] The cooling system may comprise at least one resistor configured to receive electrical current from the first motor before the electrical current powers the fan.

[0025] The least one resistor may comprise a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft.

[0026] The at least one resistor may comprise a variable resistor configured to alter the electric current reaching the fan, causing a rotation speed of the fan to be different from or equal to a rotation speed of the drive shaft.

[0027] The cooling system may comprise a switch system configured to change operation of the first motor between the first mode of operation and the second mode of operation.

[0028] The outlet may be located below the heat exchanger. The heat exchanger may be affixed to a housing of the engine.

[0029] The first motor may be configured to power the second motor to drive the fan during take-off, landing, transition, or cruise stages of flight.

[0030] The first motor may be configured to power the second motor to drive the fan when the first motor is not in use for driving the component of the aircraft other than the fan.Agent Reference: 16498-0014-00304BRIEF DESCRIPTIONS OF FIGURE AND APPENDIX IMAGES

[0031] Figure 1A illustrates an example VTOL aircraft in a cruise configuration, consistent with embodiments of the present disclosure.

[0032] Figure IB illustrates an example VTOL aircraft in a lift configuration, consistent with embodiments of the present disclosure.

[0033] Figure 2A illustrates an example boom housing a cooling fan in an air duct of a lift motor, consistent with embodiments of the present disclosure.

[0034] Figure 2B illustrates an example boom housing a cooling fan in an air duct of a tilt motor, consistent with embodiments of the present disclosure.

[0035] Figure 3A illustrates an example of a cooling fan electrically coupled to a drive shaft above a heat exchanger, consistent with embodiments of the present disclosure.

[0036] Figure 3B illustrates an example of a cooling fan electrically coupled to a drive shaft below a heat exchanger, consistent with embodiments of the present disclosure.

[0037] Figure 3C illustrates an example of a cooling fan circuit electrically coupled to a drive shaft, consistent with embodiments of the present disclosure.

[0038] Figure 3D illustrates an example of a thermostatic switch electrically coupled to a cooling fan, consistent with embodiments of the present disclosure.

[0039] Figure 4 illustrates an example of a cooling fan mechanically coupled to a drive shaft, consistent with embodiments of the present disclosure.

[0040] Figure 5A illustrates an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.

[0041] Figure 5B illustrates components of an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.

[0042] Figure 5C illustrates components of an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.

[0043] Figure 5D illustrates components of an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.

[0044] Figure 5E illustrates components of an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.

[0045] Figure 5F illustrates components of an example tilt apparatus of a VTOL aircraft, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0046] The present disclosure addresses components of electric vertical takeoff and landing(eVTOL) aircraft primarily for use in a non-conventional aircraft. For example, the eVTOLAgent Reference: 16498-0014-00304 aircraft of the present disclosure may be intended for frequent (e.g., over 50 flights per workday), short-duration flights (e.g., less than about 161 kilometers (100 miles) per flight) over, into, and out of densely populated regions. The aircraft may be intended to carry 4-6 passengers or commuters who have an expectation of low-noise and low- vibration experience. Accordingly, it may be desired that their components are configured and designed to withstand frequent use without wearing, that they generate less heat and vibration, and that the aircraft include mechanisms to effectively control and manage heat or vibration generated by the components. Further, it may be intended that several of these aircraft operate near each other over a crowded metropolitan area. Accordingly, it may be desired that their components are configured and designed to generate low levels of noise interior and exterior to the aircraft, and to have a variety of safety and backup mechanisms. For example, it may be desired for safety reasons that the aircraft are propelled by a distributed propulsion system, avoiding the risk of a single point of failure, and that they are capable of conventional takeoff and landing on a runway. Moreover, it may be desired that the aircraft can safely vertically takeoff and land from and into relatively restricted spaces (e.g., vertiports, parking lots, or driveways) compared to traditional airport runways while transporting around 4-6 passengers or commuters with accompanying baggage. These use requirements may place design constraints on an aircraft size, weight, operating efficiency (e.g., drag, energy use), which may impact on the design and configuration of the aircraft components.

[0047] Disclosed embodiments provide new and improved configurations of aircraft components that are not observed in conventional aircraft, and / or identified design criteria for components that differ from those of conventional aircraft. Such alternate configurations and design criteria, in combination addressing drawbacks and challenges with conventional components, yielded the embodiments disclosed herein for various configurations and designs of eVTOL aircraft components.

[0048] In some embodiments, the eVTOL aircraft of the present disclosure may be designed to be capable of both vertical and conventional takeoff and landing, with a distributed electrical propulsion system enabling vertical flight, forward flight, and transition. Thrust may be generated by supplying high voltage electrical power to the electrical engines of the distributed electrical propulsion system, which each may convert the high voltage electrical power into mechanical shaft power to rotate a propeller.

[0049] In preferred embodiments, the distributed electrical propulsion system may include twelve electrical engines, which may be mounted on booms forward and aft of the mainAgent Reference: 16498-0014-00304 wings of the aircraft. The forward electrical engines may be tiltable mid-flight between a horizontally oriented position (e.g., to generate forward thrust) and a vertically oriented position (e.g., to generate vertical lift). The forward electrical engines may be of a clockwise type or counterclockwise type in terms of direction of propeller rotation. The aft electrical engines may be fixed in a vertically oriented position (e.g., to generate a vertical lift). They may also be of a clockwise type or counterclockwise type in terms of direction of propeller rotation. In some embodiments, an aircraft may possess various combinations of forward and aft electrical engines. For example, an aircraft may possess six forward and six aft electrical engines, four forward and four aft electrical engines, or any other combination of forward and aft engines, including embodiments where the number of forward electrical engines and aft electrical engines are not equivalent. In some embodiments, an aircraft may possess four forward and four aft propellers, where at least four of these propellers comprise tiltable propellers.

[0050] In preferred embodiments, for a vertical takeoff and landing (VTOL) mission, the forward electrical engines as well as aft electrical engines may provide vertical thrust during takeoff and landing. During flight phases where the aircraft is in forward flight-mode, the forward electrical engines may provide horizontal thrust, while the propellers of the aft electrical engines may be stowed at a fixed position in order to minimize or reduce drag. The aft electrical engines may be actively stowed with position monitoring. Transition from vertical flight to horizontal flight and vice-versa may be accomplished via the tilt propeller subsystem. The tilt propeller subsystem may redirect thrust between a primarily vertical direction during vertical flight mode to a mostly horizontal direction during forward-flight mode. A variable pitch mechanism may change the forward electrical engine’s propeller-hub assembly blade collective angles for operation during the hover-phase, transition phase, and cruise-phase.

[0051] In some embodiments, in a conventional takeoff and landing (CTOL) mission, the forward electrical engines may provide horizontal thrust for wing-borne take-off, cruise, and landing. In some embodiments, the aft electrical engines may not be used for generating thrust during a CTOL mission and the aft propellers may be stowed in place.

[0052] In some embodiments, an electric engine may be housed or connected to a support structure of an aircraft (such as a boom, wing, tail, fuselage or other body of the aircraft) and include a motor, inverter, and gearbox. In some embodiments, the motor, inverter, and gearbox may be interfaced such that they share a central axis. In some embodiments, the torque originating in the motor may be sent away from the propellers of the propulsionAgent Reference: 16498-0014-00304 system and to a gearbox. In some embodiments, a gearbox may provide a gear reduction and then send the torque, via a main shaft, back through a bearing located inside the motor and to the propeller. In some embodiments, an inverter may be mounted on the rear of a gearbox such that a main shaft does not travel through the inverter when outputting torque to the propeller. In some embodiments, the motor, gearbox, and inverter may be interfaced such that a coolant, such as oil, may be used to service 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 may vary, including amounts less than one quart, two quarts, three quarts, or any other measured amount of oil.

[0053] It is understood that an electrical engine may generate heat during operation and may comprise a heat management system to ensure components of the electrical engine do not fail during operation. In some embodiments, coolant may be used and circulated throughout individual components of the engine, such as an inverter, gearbox, or motor, through some of the components, or through all of the components of the engine to assist with managing the heat present in the engine. Additional embodiments may include using air cooling methods to cool the electrical engine or using a mixture of coolant and air to manage the heat generated during operation in the electrical engine. In some embodiments, the coolant being used may also be the same liquid that is being used as lubricant throughout the inverter, gearbox, or motor. For example, the inverter, gearbox, and motor may be cooled using a liquid or air, or a mixture of air and liquid cooling could be used, such as cooling the motor using air cooling and using liquid cooling in the inverter and gearbox, or any other combination of air and liquid cooling across the inverter, gearbox, and motor or even subsets of those components.

[0054] In some embodiments, oil may be used as a lubricant throughout an electrical engine and may also be used as coolant fluid to assist in managing the heat generated by the engine during operation. Further to this example, different amounts of oil may be used to act as both lubricant and coolant fluid in the electrical engine, such as less than one quart, less than two quarts, or any other amount of oil needed to lubricate and cool the electrical engine, in combination with or without the assistance of air cooling. As has been disclosed herein, an electrical engine may have different primary functionalities such as being used only for lifting and landing, and as such only being used in one orientation, or being used during all stages of flight such as lifting, landing, and in-flight. An engine that is used in all stages of flight may experience various orientations throughout flight and may comprise more lubricant and coolant than the engine only used in one orientation. As such, all the engines on an aircraft may not include the same amount of lubricant and coolant. For example, a liftingAgent Reference: 16498-0014-00304 and landing engine may only require less than one quart of oil while an engine that operates in all stages of flight may require more than one quart of oil. It should be understood that the example embodiments, as mentioned herein, are representative and do not dictate the bounds of the amount of lubricant and coolant that may be used in an electrical engine.

[0055] Cooling systems often rely on active cooling that involves separate electrical and mechanical components to control liquid or air cooling and direct heat away from an engine during operation. These components may run separately from the engine, requiring control electronics, power supplies, cabling, and various other additional components to operate the active cooling system. Each of these components requires space and contributes to a net weight of a device or apparatus. In some cases, this may not be a problem. However, when implemented in aircrafts in particular, the additional weight and space requirements of an active cooling system may be detrimental to the energy efficiency and effectiveness of operating an aircraft. However, it may be challenging to dispense with such active cooling systems in eVTOL aircraft because, during lift and hover phases of eVTOL flight, passive sources air flow may be insufficient.

[0056] For example, a passive cooling system may be configured to pass air flow generated by propeller downwash, or other aircraft movement, into a channel and through a heat exchanger. However, such a system may not always provide sufficient airflow due to, e.g., cross-winds or heightened cooling requirements, and may present unpredictable variability with regard to air flow. Thus, passive cooling systems may be inadequate.

[0057] For this reason, a cooling fan may be added to a passive system, such as by coupling the fan to the propeller shaft directly such that when the motor rotates the shaft, the cooling fan also rotates around the same axis. However, such a configuration may impose unwanted design constraints on the arrangement of, e.g., an engine, heat exchanger or air duct. For example, it may be difficult to obtain adequately cool air to deposit heat energy from hot air from the engine, driven by the cooling fan in this configuration. Furthermore, such a configuration may not allow the rotational speed of the cooling fan to be varied relative to the shaft.

[0058] Embodiments of the present disclosure may provide a passive cooling system using a cooling fan placed off-axis from the propeller shaft. When a VTOL with such a passive cooling system begins to move, air may flow through an air duct with a cooling fan. The cooling fan may be located in an air duct of, e.g., a lifter of a VTOL allowing greater airflow through a heat exchanger. The cooling fan may be located off-axis from the motor axis of rotation and may be oriented at any angle relative to the motor axis. The cooling fan may beAgent Reference: 16498-0014-00304 electrically or mechanically coupled to a propeller motor such that when the propeller rotates, the cooling fan also rotates. These embodiments may provide a passive cooling system that is lightweight and energy efficient, and does not require any added control architecture. Some embodiments of the present disclosure may provide for a cooling fan mechanically or electrically coupled to a motor configured to drive a component of the aircraft other than the fan in a first mode of operation. For example, the cooling fan may be mechanically or electrically coupled to a pitch control motor of a pitch control apparatus.

[0059] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the disclosure. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the subject matter recited in the appended claims.

[0060] Figs. 1A-B illustrate a VTOL aircraft 100 in a cruise configuration and a vertical take-off, landing and hover configuration (also referred to herein as a “lift” configuration), respectively, consistent with embodiments of the present disclosure. Aircraft 100 may include a fuselage 102, wings 104 mounted to fuselage 102, tail 105, and one or more rear stabilizers 106 mounted to tail 105 or the rear of fuselage 102. A plurality of lift propellers 112 may be mounted to wings 104 and configured to provide lift for vertical take-off, landing and hover. A plurality of tilt propellers 114 may be mounted to wings 104 and may be tiltable between the cruise configuration in which they provide forward thrust to aircraft 100 for horizontal flight, as shown in Fig. 1A, and the lift configuration in which they provide a portion of the lift required for vertical take-off, landing and hovering, as shown in Fig. IB. As used herein, a lift configuration may refer to a tilt propeller orientation in which the tilt propeller thrust is providing primarily lift to the aircraft. A cruise configuration may refer to a tilt propeller orientation in which the tilt propeller thrust is providing primarily forward thrust to the aircraft. Alternatively, a cruise configuration may refer to a configuration in which a lift propeller is stowed.

[0061] In some embodiments, lift propellers 112 may be configured for providing lift only, with all propulsion being provided by the tilt propellers. Accordingly, lift propellers 112 may be in fixed positions and may only generate thrust during take-off, landing and hover. Meanwhile, tilt propellers 114 may be tilted to lift configurations in which their thrust is directed vertically for providing additional lift.Agent Reference: 16498-0014-00304

[0062] For forward flight, tilt propellers 114 may tilt from their lift configurations to their cruise configurations. In other words, the pitch and tilt angle of tilt propellers 114 may be varied from an orientation in which the tilt propeller thrust is directed vertically (to provide lift during vertical take-off, landing and hover) to an orientation in which the tilt propeller thrust is directed horizontally (to provide forward thrust to aircraft 100). The tilt propellers may tilt about axes that may be perpendicular to the forward direction of aircraft 100. When aircraft 100 is in full forward flight during the cruise configuration, lift may be provided entirely by wings 104. Meanwhile, lift propellers 112 may be shut off. Blades 120 of lift propellers 112 may be locked in low-drag positions for aircraft cruising. In some embodiments, lift propellers 112 may each have two blades 120 that may be locked for cruising in minimum or reduced drag positions in which one blade is directly in front of the other blade as illustrated in Fig. 1A. In some embodiments, lift propellers 112 have more than two blades. In some embodiments, tilt propellers 114 include more blades 118 than lift propellers 112. For example, as illustrated in Figs. 1A-B, lift propellers 112 may each include, e.g., two blades and tilt propellers 114 may each include, e.g., five blades. In some embodiments, tilt propellers 114 may have, e.g., from 2 to 5 blades.

[0063] In some embodiments, the aircraft may include only one wing 104 on each side of fuselage 102 (or a single wing that extends across the entire aircraft) and at least a portion of lift propellers 112 may be located rearward of wings 104 and at least a portion of tilt propellers 114 may be located forward of wings 104. In some embodiments, all of lift propellers 112 may be located rearward of wings 104 and all of tilt propellers 114 may be located forward of wings 104. According to some embodiments, all lift propellers 112 and tilt propellers 114 may be mounted to the wings — i.e., no lift propellers or tilt propellers may be mounted to the fuselage. In some embodiments, lift propellers 112 may be all located rearwardly of wings 104 and tilt propellers 114 may be all located forward of wings 104. According to some embodiments, all lift propellers 112 and tilt propellers 114 may be positioned inwardly of wing tips 109.

[0064] In some embodiments, lift propellers 112 and tilt propellers 114 may be mounted to wings 104 by booms 122. Booms 122 may be mounted beneath wings 104, on top of the wings, and / or may be integrated into the wing profile. In some embodiments, one lift propeller 112 and one tilt propeller 114 may be mounted to each boom 122. Lift propeller 112 may be mounted at a rear end of boom 122 and tilt propeller 114 may be mounted at a front end of boom 122. In some embodiments, lift propeller 112 may be mounted in a fixed position on boom 122. In some embodiments, tilt propeller 114 may mounted to a front endAgent Reference: 16498-0014-00304 of boom 122 via a hinge. Tilt propeller 114 may be mounted to boom 122 such that tilt propeller 114 is aligned with the body of boom 122 when in the cruise configuration, forming a continuous extension of the front end of boom 122 that minimizes or reduces drag for forward flight.

[0065] In some embodiments, aircraft 100 may include, e.g., one wing on each side of fuselage 102 or a single wing that extends across the aircraft. According to some embodiments, at least one wing 104 is a high wing mounted to an upper side of fuselage 102. According to some embodiments, the wings include control surfaces, such as flaps, ailerons or flaperons. According to some embodiments, the wings may have curved wing tips 109 for reduced drag during forward flight.

[0066] In some embodiments, rear stabilizers 106 include control surfaces, such as one or more rudders, one or more elevators, and / or one or more combined rudder-elevators. The wing(s) may have any suitable design. For example, the wings have a tapering leading edge or a tapering trailing edge. In some embodiments, the wings may have a substantially straight leading edge in the central section of wings 104.

[0067] Aircraft 100 may include at least one door 110 for passenger entry and exit. In some embodiments, door 110 may be located beneath and forward of wings 104 as seen in Figs. 1A-B.

[0068] Further discussion of VTOL aircraft may be found in U.S. Patent Publication No. 2021 / 0362849, which is incorporated by reference in its entirety for all purposes.

[0069] As discussed above, operation of a motor or engine produces substantial heat that should be dissipated to protect the various electrical and mechanical components. With respect to a VTOL, the engine or motor driving lift propeller 112 or tilt propeller 114 would benefit from an active or passive cooling system involving a heat exchanger, cooling fan (or fan), and air duct. “Passive” may refer to a system or device that operates without dedicated or independent control architecture or power supplies for its operation. For example, a passive cooling system for a propeller motor may comprise a cooling fan that relies on the rotational action of the motor drive shaft to drive the cooling fan whenever the motor is in operation. Such a passive arrangement may reduce the number of required components without sacrificing cooling effectiveness, thereby increasing the reliability of aircraft components, reducing the weight of aircraft 100, and improving energy efficiency.

[0070] Fig. 2A illustrates an example boom 122 housing cooling fan 214 (also referenced as a fan) in air duct 208, consistent with embodiments of the present disclosure. As discussed with reference to Figs. 1A-B above, boom 122 may comprise a structural component ofAgent Reference: 16498-0014-00304 aircraft 100 located at any orientation forward or backward of wings 104 and mounted to lift propeller 112 or tilt propeller 114. Boom 122 may be configured to house, e.g.: engine 202 configured to rotate drive shaft 204 driving a propeller, heat exchanger 206 coupled to engine 202, and air duct 208 configured to direct cooling air 210 from inlet 212, through cooling fan 214 and heat exchanger 206, to outlet 216 to be exhausted out of boom 122.

[0071] Boom 122 is shown in Fig. 2A in one exemplary configuration and shape but may comprise any number of other possible shapes and configurations. For example, as discussed previously, while illustrated boom 122 depicts a lift propeller apparatus, embodiments of the present disclosure may be configured as a tilt propeller 114 and may be mounted with a hinge to allow tilt propeller 114 to rotate between a lift configuration and a cruise configuration. A plurality of booms 122 on aircraft 100 may include a plurality of engines 202 mounted directly to propeller shafts to drive the propellers. In some embodiments, a plurality of propeller shafts may be driven by a single engine 202 using a series of shafts or transmissions.

[0072] Disclosed embodiments may include drive shaft 204 configured to drive a propeller. As used herein, drive shaft 204 may be any shaft operated by an engine or motor and configured to rotate about an axis and to provide rotational energy to another component in the system (e.g., a prop shaft driving a propeller in aircraft 100 or an automobile drive shaft connecting a transmission to the drive wheels or axles). Drive shaft 204 may operate to rotate another shaft which then rotates another component, such as a propeller or wheel.

[0073] Disclosed embodiments may include engine 202 configured to rotate drive shaft 204. In some embodiments, engine 202 may be located inside boom 122. In some other embodiments, engine 202 may be located outside of boom 122 and configured to drive the drive shaft 204 to rotate a propeller. As discussed previously, engine 202 may comprise an electric engine, which may include a motor used to drive a propeller. The electric engine may include a motor connected to an inverter, as discussed previously. This configuration allows for the motor to control variable speed and torque of drive shaft 204.

[0074] Disclosed embodiments may include heat exchanger 206 thermally coupled to engine 202 and mechanically coupled to air duct 208. Heat exchanger 206 may remove heat from engine 202 or the engine. Coupling heat exchanger 206 may involve direct mounting to engine 202. In some embodiments, heat exchanger 206 may be affixed or otherwise mechanically coupled to the housing of engine 202. In some embodiments, heat exchanger 206 may be thermally coupled to engine 202 through tubing or channels traversed by heat- conductive fluids to transfer heat energy from engine 202 to heat exchanger 206. Such tubingAgent Reference: 16498-0014-00304 may allow greater design freedom in the placement of heat exchanger 206 in boom 122 or elsewhere. Heat exchanger 206 may be located inside air duct 208 to allow cooling air 210 to travel through heat exchanger 206 to remove and exhaust heat from boom 122. In some embodiments, heat exchanger 206 may comprise cooling fins to provide a large overall surface area contact with cooling air 210.

[0075] Disclosed embodiments may include air duct 208 in aircraft 100. Air duct 208 may comprise, e.g., a channel or other pathway allowing air to pass from inlet 212, through cooling fan 214 and heat exchanger 206, and to outlet 216. For example, in some embodiments, the channel may comprise the full interior volume of boom 122, or may be formed by baffles or partitions inside boom 122. In some embodiments, as illustrated, air duct 208 may comprise ductwork or other conduits configured to optimize airflow characteristics through the various components, such as fan 214 and heat exchanger 206. Air duct 208 may include inlet 212 and outlet 216. Inlet 212 and outlet 216 are shown in one exemplary configuration in Fig. 2A but may be positioned in any configuration above or below boom 122. Inlet 212 and outlet 216 may comprise openings in boom 122 allowing ambient cooling air 210 to flow into inlet 212 and out of outlet 216. A baffle may be used to control the direction or type of cooling air 210 through air duct 208. Cooling air 210 may comprise prop wash from the propeller’s rotation, airflow from the movement of aircraft 100, ambient air pulled into inlet 212 by cooling fan 214, or some combination thereof. In some embodiments, cooling air 210 may be separate from the prop wash. For example, inlet 212 may be located on a surface opposite the propeller or in some other orientation that inhibits prop wash from entering the inlet. Various orientations and positions of inlet 212 or outlet 216 on boom 122 may be implemented. In some embodiments, outlet 216 may be located below heat exchanger 206. Below heat exchanger 206 may refer to being located toward the lower part of aircraft 100. In some other embodiments, outlet 216 or inlet 212 may be located above heat exchanger 206. In yet other embodiments, outlet 216 or inlet 212 may be located adjacent to heat exchanger 206.

[0076] Disclosed embodiments may include cooling fan 214 in air duct 208 rotating about an axis different from the axis of rotation of drive shaft 204. The two axes may be noncollinear (i.e., not along the same line). In some embodiments, the rotational axis of cooling fan 214 may be laterally displaced from the rotational axis of drive shaft 204. For example, the two axes may be parallel but offset horizontally in boom 122. In some embodiments, the two axes may be oriented perpendicular to one another. For example, Fig. 2A illustrates cooling fan 214 rotating about a horizontal axis, while drive shaft 204 rotates about a vertical axis. InAgent Reference: 16498-0014-00304 some other embodiments, cooling fan 214 may rotate about an axis at some angle between horizontal and vertical relative to the rotational axis of drive shaft 204. For example, cooling fan 214 may be at a diagonal angle. The two axes may be oriented at any relative angle in three dimensions such that cooling fan 214 may direct cooling air 210 toward any direction. For example, the intersection point of the two rotational axes may form any angle from 0-360 degrees in the plane of Fig. 2A and any angle from 0-360 degrees into or out of the plane of Fig. 2A

[0077] Cooling fan 214 may comprise an axial fan, a centrifugal fan, or a mixed-flow fan operating using a DC motor or an AC motor. Cooling fan 214 may be mounted in the center of air duct 208 or at any position or orientation in air duct 208. In some embodiments, cooling fan 214 may be placed along a central axis of air duct 208. Cooling fan 214 may be oriented at any angle relative to the central axis of air duct 208. Cooling fan 214 may be located anywhere along the length of air duct 208. For example, cooling fan 214 may be located near inlet 212, near outlet 216, or anywhere in between. In some embodiments, cooling fan 214 may be located at the nacelle of boom 122 or outside the nacelle of boom 122.

[0078] In some embodiments, cooling fan 214 may be configured as a primary or singular source of cooling airflow. In some embodiments, cooling fan 214 may comprise an auxiliary fan configured to increase the speed or volumetric flow rate of existing airflow provided by, e.g., prop wash entering inlet 212.

[0079] In some embodiments, cooling fan 214 may comprise a single fan. In some embodiments, cooling fan 214 may comprise a plurality of cooling fans operating together using power provided by rotation of drive shaft 204. For example, a pair of cooling fans may be positioned in locations separated distally through air duct 208, such that one cooling fan may be located closer to inlet 212 and the other cooling fan may be located closer to outlet 216. In some embodiments, at least one cooling fan may be located between inlet 212 and heat exchanger 206, and at least one other cooling fan may be located between outlet 216 and heat exchanger 206. In some embodiments, a plurality of cooling fans may be located adjacent to one another at the same location distally along air duct 208. For example, a pair of cooling fans may exist side-by-side in air duct 208 and be located symmetrically about a central axis in air duct 208. In some embodiments, a cooling fan may be configured to draw air from a separate auxiliary inlet (not shown) and direct the air into duct 208 or to heat exchanger 206. In some embodiments, a plurality of cooling fans may be controlled synchronously, such that the cooling fans operate together at the same rotational speed. InAgent Reference: 16498-0014-00304 some other embodiments, a plurality of cooling fans may be controlled asynchronously. For example, one cooling fan may rotate at twice the rotational speed as another cooling fan.

[0080] In some embodiments, a hinged door may be mounted in the nacelle of boom 122 to allow intake of cooling air 210 in crosswind. A hinged door may protect air duct 208 from debris in some conditions. The hinged door may be actuated using a switch or other method through a controller or central computer on aircraft 100.

[0081] Fig. 2B illustrates example boom 122 housing cooling fan 214 in air duct 208, consistent with embodiments of the present disclosure. As discussed with reference to Figs. 1A-B above, boom 122 may comprise a structural component of aircraft 100 located at any orientation forward or backward of wings 104 and mounted to lift propeller 112 or tilt propeller 114. Boom 122 of Fig. 2B is illustrated as mounted to a tilt propeller 114, and may be configured to house, e.g.: engine 202 configured to rotate drive shaft 204 driving a propeller, heat exchanger 206 coupled to engine 202 (not shown), and air duct 208 configured to direct cooling air 210 from inlet 212, through cooling fan 214 and heat exchanger 206, to outlet 216 to be exhausted out of boom 122. Tilt propeller 114 is illustrated in a tilted and untilted configuration. Direction of travel is indicated by arrow 220. During transition between take-off and cruise flight, tilt propeller 114 moves from the tilted to un-tilted configuration.

[0082] Figs. 3A-B illustrate examples of cooling fan 214 electrically coupled to drive shaft 204 above or below heat exchanger 206, consistent with embodiments of the present disclosure. Electrical coupling of cooling fan 214 to drive shaft 204 may include wiring 302 connecting cooling fan 214 to stator 304 or rotor 306. Stator 304 and rotor 306 may comprise a generator that is separate and distinct from a stator-rotor combination used to drive the drive shaft 204. For example, in some embodiments, rotor 306 may comprise an array of permanent magnets whose rotation by drive shaft 204 may produce an electric current in windings of stator 304. Stator 304 and rotor 306 may comprise electrical components surrounding drive shaft 204, such as magnets, coils or windings, etc.

[0083] In Fig. 3A, stator 304 and rotor 306 are shown to be mounted adjacent to drive shaft 204 above heat exchanger 206 in the area of drive shaft 204 near the propeller. In Fig. 3B, stator 304 and rotor 306 are shown to be mounted adjacent to drive shaft 204 below heat exchanger 206 in the area of drive shaft 204 opposite the propeller. Figs. 3A-B are merely example implementations of some of the disclosed embodiments and are not intended to be limiting. Wiring 302 making an electrical connection between stator 304 and cooling fan 214 may be positioned loosely or may be secured to any part of engine 202, air duct 208, or another component in boom 122. For example, wiring 302 may be secured to the housing ofAgent Reference: 16498-0014-00304 engine 202, and may traverse an opening in air duct 208 to a mount for cooling fan 214. Cooling fan 214 may be any type of fan and may be positioned to direct air through air duct 208 in any direction.

[0084] In some embodiments, rotor 306 may comprise a cylindrical shaped component with at least one magnet (i.e. a magnet array), and this component may be mounted around drive shaft 204. In some embodiments, rotor 306 may comprise individual magnets mounted to drive shaft 204. In some other embodiments, rotor 306 may include one or more coiled insulated wires. Rotor 306 may be mounted to drive shaft 204. In some embodiments drive shaft 204 may act as rotor 306. For example, magnets or coiled wire may be integrated into part of drive shaft 204. The magnets may comprise permanent magnets or magnets that are formed when current travels through coils or windings. The number of magnets or coiled insulated wires may be proportional to the number of poles of rotor 306.

[0085] In some embodiments, stator 304 may be a cylindrical shaped component mounted to, e.g., the housing of engine 202 or a component that is stationary with respect to the housing. Stator 304 may be located adjacent to rotor 306. In some embodiments, stator 304 may include one or more coiled insulated wires. In some embodiments, stator 304 may include one or more magnets. The number of magnets or coiled insulated wires may be proportional to the number of poles of stator 304.

[0086] Together, stator 304 and rotor 306 may act as an induction motor or generator, producing electricity during operation. When drive shaft 204 rotates, rotor 306 also rotates, which causes stator 304 to generate an electric current traveling through at least one wire of wiring 302 to power cooling fan 214. This production of current from the rotation of drive shaft 204 may allow stator 304 and rotor 306 to act as a generator providing current to power cooling fan 214, preventing the need for a separate power source or control architecture for cooling fan 214. For example, stator 304 may produce a magnetic field around rotor 306, and stator 304 may have coiled wires mounted to drive shaft 204 such that when rotor 306 rotates, the magnetic field of stator 304 induces current to flow. The result is a cooling fan that operates only when needed, as heat is primarily generated only when engine 202 is running.

[0087] In some embodiments, the generator may comprise an AC motor, including an induction motor or a synchronous motor, driven by drive shaft 204. An AC motor may be single or poly phase and single or multi-pole. An AC induction motor used as a generator may use the rotational speed of drive shaft 204 to vary the rotational speed of cooling fan 214. For example, a squirrel-cage induction rotor may be used in an AC induction motor and the speed-torque characteristics may be controlled by reshaping the rotor bars on the squirrel-Agent Reference: 16498-0014-00304 cage rotor. The electrical frequency generated by an AC motor may directly related to the number of pole pairs in rotor 306 or stator 304. Depending on the type of fan used for cooling fan 214, rotational speed of cooling fan 214 may be proportional to electrical frequency. If cooling fan 214 operates on DC, a rectifier circuit may be used to convert AC to DC.

[0088] In some embodiments, the generator may comprise a DC motor, including a brushed or brushless motor. A brushed DC motor may be used with a commutator rotating in synchronization with rotor 306. For example, a commutator may be located below drive shaft 204 (e.g. at the bottom of Fig. 3B). A brushless DC motor may include coiled wires in stator 304 or rotor 306. The number of pairs of coiled wires may be equal to the number of poles. Alternatively, the number of pairs of magnets on stator 304 or rotor 306 may be equal to the number of poles. In some embodiments, a brushless DC motor may be used with a number of poles controlling the rotational speed of cooling fan 214. For example, the frequency of the current output by the brushless DC motor may be varied by the number of pole pairs, and the rotational speed of cooling fan 214 may be proportional to the frequency.

[0089] For DC or AC motors, generated voltage may be related to the number of windings of coils, the strength of the magnetic field, or the rotational speed of drive shaft 204. Cooling fan 214 may operate at a constant voltage, or may operate at a variable voltage. For a variable voltage, the generated voltage may be allowed to vary to control the rotational speed of cooling fan 214. For example, as the rotational speed of drive shaft 204 increases, the voltage powering cooling fan 214 increases, thus increasing the rotational speed of cooling fan 214. This variable voltage control of fan speed may also be combined with a variable frequency control of fan speed that may occur when the frequency traveling through wiring 302 varies with rotational speed of drive shaft 204.

[0090] Other means for controlling fan speed may be implemented in combination with the above. In some embodiments, a DC rectifier circuit may be used to convert AC to DC from the generator. For example, cooling fan 214 may operate using DC but the AC or DC generator may produce AC. In some embodiments, a transformer may be used to reduce or increase voltage from the generator.

[0091] In some embodiments, at least one resistor may be configured to receive electrical current from the first motor or the second motor before the electrical current powers the fan. A resistor may be used to reduce the current reaching cooling fan 214. In some embodiments, a static resistor may be used to change the rotational speed of cooling fan 214 relative to the rotational speed of drive shaft 204. For example, the current may be reduced in proportion to a voltage drop across the resistor, or in proportion to the resistance of the resistor. In someAgent Reference: 16498-0014-00304 embodiments, the resistor may comprise a variable resistor used to vary the rotational speed of cooling fan 214. For example, the variable resistor may comprise a potentiometer controlled electronically (e.g., remotely) or through a manual dial. In some embodiments, the variable resistor may alter current reaching cooling fan 214 such that the rotation speed of cooling fan 214 is different from the rotation speed of drive shaft 204.

[0092] Current reaching cooling fan 214 may be converted to rotational energy for rotating cooling fan 214 using a DC motor or an AC motor, as described previously with regards to the generator embodiments. For example, when current reaches cooling fan 214, the current may drive coils of rotor 306 to produce a magnetic field that interacts with the magnetic field of stator 304, causing rotor 306 to rotate, which rotates cooling fan 214. Using a DC motor or an AC motor, cooling fan 214 may rotate with a rotational speed inversely proportional to the number of pole pairs, or proportional to the current frequency (for AC) or current amplitude. A combination of these and other variables, including other electrical components such as resistors, may be designed to provide an ideal rotation speed for each cooling fan 214. Furthermore, any electrical component, including cooling fan 214 may be disengaged or turned off at any time. For example, during cruising of aircraft 100, downwash may provide sufficient cooling air 210 such that cooling fan 214 is not needed, and cooling fan 214 may be turned off.

[0093] In some embodiments, the rotational speed of cooling fan 214 may be controlled by a difference in poles of cooling fan 214 relative to the generator. For example, the number of coil windings in a brushless DC motor controlling cooling fan 214 may be related to a pole count in cooling fan 214, and the number of coil windings in the generator may be related to a pole count in the generator, and the difference in the pole count may directly related to the relative rotational speeds of drive shaft 204 and cooling fan 214.

[0094] Fig. 3C illustrates an example of a cooling fan electrically coupled to a drive shaft, consistent with embodiments of the present disclosure. Rotor 306 may be configured to rotate from rotation of, e.g., a drive shaft (such as drive shaft 204 of Figs. 2-3B). This rotation may provide electric current via stator 304, as described previously. In this example, stator 304 may provide AC power through AC wires 308 to rectifier 310, which may convert the AC to DC power and deliver it through DC wires 312 to cooling fan circuit 314. In alternative configurations, rotor 306 and stator 304 may produce DC power, and rectifier 310 may be omitted. Cooling fan circuit 314 may include components such as processor 316, capacitor 318, voltage regulator 320, and gate driver 322 used to drive a fan motor 307 (second motor) to rotate cooling fan 214. Cooling fan circuit 314 may include a plurality of any of theseAgent Reference: 16498-0014-00304 components, and the quantity of any circuit component is illustrated only for explanatory purposes. Cooling fan circuit 314 may be electrically coupled to an ambient temperature sensor 324 and device temperature sensor 326. Cooling fan circuit 314 may include a plurality of temperature sensors (not shown) for device or ambient temperature measurements. Ambient temperature sensor 324 may be located to measure air temperature outside an aircraft.

[0095] The temperature sensors used in disclosed embodiments, including device temperature sensor 326 and ambient temperature sensor 324, may be any device capable of measuring temperature. The temperature sensors may be digital or analog sensors. For example, a digital temperature sensor may detect temperature and convert the temperature to a digital signal before sending the digital signal to cooling fan circuit 314. An analog temperature sensor may detect temperature and send a continuous signal (e.g., analog signal) to cooling fan circuit 314, which may then convert the analog signal to a digital value. The temperature sensors may include, e.g., thermocouples, thermistors, resistance temperature detectors, semiconductor temperature sensors, infrared sensors, thermomagnetic sensors, or fiber optic temperature sensors.

[0096] In some embodiments, rotor 306 and stator 304 may form a generator configured to vary speed of cooling fan 214 by coupling device temperature sensor 326 to cooling fan circuit 314. Cooling fan circuit 314 may be configured to drive a fan motor 307 (second motor) of cooling fan 214. When ambient temperature or device temperature changes, cooling fan circuit 314 may adjust the rotational speed of cooling fan 214. For example, device temperature sensor 326 may be configured to detect the temperature of a heat exchanger, an engine, a part of a housing for the engine or a propeller, as described previously. Ambient temperature may include a measurement of temperature in the surrounding environment or air, such as air flowing through an air duct, as described previously.

[0097] In some embodiments, cooling fan circuit 314 may be configured to detect a first temperature from ambient temperature sensor 324 and a second temperature from device temperature sensor 326 and adjust an operation parameter, such as activation state or rotational speed of cooling fan 214, according to the difference in the first temperature and the second temperature. For example, if the first temperature is higher than the second temperature, then cooling fan 214 may be shut off. If the first temperature is lower than the second temperature, then cooling fan circuit 314 may increase rotational speed of cooling fanAgent Reference: 16498-0014-00304214. Various combinations of the first temperature and the second temperature may result in various cooling fan speeds.

[0098] In some embodiments, cooling fan circuit 314 may be configured to increase rotational speed of cooling fan 214 when a temperature measured by device temperature sensor 326 is above a preestablished threshold. The preestablished threshold may be related to a safety temperature for a part, such as an engine, or the threshold may be related to optimization of part functions. For example, device temperature sensor 326 may be located in an engine (e.g., engine 202 of Figs. 2-3B) to measure the temperature of the engine and when the engine temperature is above the preestablished threshold, the speed of cooling fan 214 may be increased to reduce the temperature of engine. For example, device temperature sensor 326 may be located in a heat exchanger in an air duct (e.g., heat exchanger 206 and air duct 208 of Figs. 2-3B) to measure the temperature of the heat exchanger and compare to ambient temperature of air in the air duct or outside air to determine the speed of cooling fan 214. In this example, the heat exchanger temperature may be determined to be below the preestablished threshold, and ambient air may be determined to be below freezing, so cooling fan 214 may be turned off.

[0099] Fig. 3D illustrates an example of a thermostatic switch electrically coupled to a cooling fan, consistent with embodiments of the present disclosure. Rotor 306 may be configured to rotate from rotation of, e.g., a drive shaft (such as drive shaft 204 of Figs. 2- 3B). This rotation may provide electric current via stator 304, as described previously. In this example, rotation of rotor 306 in stator 304 may generate current through wires 308 to drive cooling fan 214. Wires 308 may traverse various locations in and around an engine, housing, heat exchanger, etc. Thermostatic switch 330 may be located somewhere along wires 308 between stator 304 and cooling fan 214. For example, thermostatic switch 330 may be located in an engine housing. For example, when the temperature is above a predetermined threshold, the switch may close, providing current to cooling fan 214. Such a thermostatic switch may be binary (e.g., open or closed). In some embodiment, thermostatic switch 330 may be variable. For example, thermostatic switch 330 may alter current reaching cooling fan 214 depending on the measured temperature.

[0100] An example embodiment corresponding to Figs. 3A-D is described by the following: aircraft 100 begins lifting off the ground, using lift propellers 112 and tilt propellers 114 in lift configuration. Engine 202 operating drive shaft 204 produces heat which is transferred to heat exchanger 206. Air duct 208 allows cooling air to enter inlet 212, passing through cooling fan 214 and heat exchanger 206 to be exhausted out of outlet 216. While rotating,Agent Reference: 16498-0014-00304 drive shaft 204 rotates mounted rotor 306, which rotates adjacent to stator 304, causing current to be generated. The current travels through wiring 302 to cooling fan circuit 314, which determines from ambient temperature sensor 324 and device temperature sensor 324 to rotate cooling fan 214 at a particular speed to increase the flow of cooling air 210 through air duct 208. The use of cooling fan 214 helps increase the rate of heat released by heat exchanger 206, increasing the cooling rate for engine 202. The increased cooling rate helps to increase the performance and longevity of the mechanical and electrical components within boom 122 or aircraft 100.

[0101] Fig. 4 illustrates an example of cooling fan 214 mechanically coupled to drive shaft 204, consistent with embodiments of the present disclosure. Engine 202 may drive the drive shaft 204 to rotate a propeller. Drive pulley 402 in belt drive 404 may be mounted to drive shaft 204 such that when drive shaft 204 rotates, drive pulley 402 rotates. In belt drive 404, drive pulley 402 may connect a fan belt (not shown) to one or more drive pulleys, such as drive pulley 402. A driven pulley may connect through fan shaft 406 to cooling fan 214. When drive shaft 204 rotates, drive pulley 402 may rotate, causing a fan belt to move around driven pulley 402 and one or more driven pulleys, which may cause one or more cooling fans 214 to rotate, driving cooling air 210 through air duct 208.

[0102] Belt drive 404 may include a fan belt, gears, or several pulleys, including drive pulley 402 and driven pulleys. Additional pulleys may be intermediary pulleys, and various tensioners used to keep the fan belt under tension. Tension clamps may be used to hold the tensioners in place. The pulleys may be toothed or untoothed and engage the belt, which may be toothed or untoothed. The fan belt may be a flat belt, V-belt, or synchronous belt. The inner side of the fan belt engaging with the pulleys may have edges or grooves to reduce slippage.

[0103] The pulleys may have various diameters. In some embodiments, the rotation speed of cooling fan 214 may be different from the rotation speed of drive shaft 204. The rotation speed of cooling fan 214 may be determined from the speed ratio of the diameter of drive pulley 402 to the diameter of a driven pulley driving cooling fan 214. In some embodiments, drive pulley 402 may be the largest pulley in belt drive 404. In some other embodiments, drive pulley 402 may be smaller than a driven pulley. Such a configuration may allow for cooling fan 214 to rotate slower than drive shaft 204. In some embodiments, a driven pulley may have a diameter identical to drive pulley 402. Pulleys with equivalent diameters driven by a fan belt may rotate at the same speed. In some embodiments, the rotation speed of cooling fan 214 may be equal to the rotation speed of drive shaft 204.Agent Reference: 16498-0014-00304

[0104] Belt drive 404 may include a plurality of belts and a plurality of pulleys. The plurality of belts may be coupled to various combinations of pulleys to vary speed ratios for one or more cooling fans 214. For example, a larger pulley may be mounted adjacent to a smaller pulley, forming a combination pulley, such that both pulleys of the combination pulley rotate together. In this example, a first fan belt may engage the larger pulley, and a second fan belt may engage the smaller pulley. In some embodiments, a third pulley may be used to change the rotation speed of cooling fan 214 relative to the rotation speed of drive shaft 204. The third pulley may be a combination pulley, as described above, connecting a first fan belt to drive pulley 402 and a second fan belt to drive a driven pulley to rotate cooling fan 214. A combination pulley may be one example implementation of this embodiment, and alternatively other combinations of intermediate pulleys between drive pulley 402 and the driven pulleys may be used.

[0105] In some embodiments, a fan belt may be coupled to a gearbox to change the rotation speed of cooling fan 214 relative to the rotation speed of drive shaft 204. The gearbox may contain a plurality of gears of different diameters which act together to provide various speed ratios. The gearbox may be a gear hub with different gear ratios used to vary the speed of cooling fan 214. The gearbox may be located anywhere in belt drive 404 and used to change the rotation speed of a pulley or shaft 406. In some embodiments, a gearbox may interface directly with shaft 406 to rotate cooling fan 214 variably. The gearbox may be electronically controlled in aircraft 100. For example, a pilot may choose to increase the gear ratios to increase cooling fan speed before lifting aircraft 100. In some embodiments, the gearbox may automatically shift gears to vary the rotation speed of cooling fan 214 depending on engine 202 temperature. For example, engine 202 or heat exchanger 206 may be fitted with various temperature sensors to measure temperature continuously or on-demand.

[0106] An example embodiment corresponding to Fig. 4 may be described by the following: aircraft 100 begins lifting off the ground, using lift propellers 112 and tilt propellers 114 in lift configuration. Engine 202 operating drive shaft 204 produces heat which is transferred to heat exchanger 206. Air duct 208 allows cooling air to enter inlet 212, passing through cooling fan 214 and heat exchanger 206 to be exhausted out of outlet 216. While rotating, drive shaft 204 rotates drive pulley 402 in tandem, which causes a fan belt to begin moving. The fan belt passes by several tensioners to a gearbox pulley, which is connected through shaft 406 to cooling fan 214, causing cooling fan 214 to rotate and increase the flow of cooling air 210 through air duct 208. Due to an increase in temperature, the gear ratios are increased to increase the rotational speed of cooling fan 214. The use of cooling fan 214Agent Reference: 16498-0014-00304 helps increase the rate of heat released by heat exchanger 206, increasing the cooling rate for engine 202. The increased cooling rate helps to increase the performance and longevity of the mechanical and electrical components within boom 122 or aircraft 100.

[0107] Some embodiments described in association with Figs. 3-4 may be automated. Automated approaches may include adjusting the gearbox automatically or adjusting current to cooling fan 214 automatically using preprogrammed algorithms based on previously obtained data associated with heat generation by engine 202 during different flight phases. For example, temperature feedback from temperature sensors may be provided to a central computer in aircraft 100, which may choose to adjust a gear ratio or current accordingly. For example, reducing or turning off cooling fan 214 when the temperature of engine 202 is in an acceptable range may provide energy-saving benefits. Some embodiments described in association with Figs. 3-4 may comprise fixed settings, such as fixed gear ratios or current supplies that are not actively adjustable.

[0108] In some embodiments, cooling fan 214 may be powered by a motor of a pitch control apparatus. Figs. 5A-5F illustrate embodiments including a pitch control apparatus. The embodiments of Figs. 5A-5F include motors which may be used to power cooling fan 214.

[0109] Fig. 5A illustrates a pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B.

[0110] Tilt apparatus 500 may comprise pitch control system 510, rotor drive system 540, and pitch drive system 560. Pitch control system 510 may comprise pitch control rod 550, yoke 522, ball nut 514, thrust bearing 524, clutch mechanism 570, output shaft 572, control unit 576, and / or feedback sensors 564, 574.

[0111] Hub 512 may be configured to house plurality of blade bearings 516, yoke 522, ball nut 514, thrust bearing 524, and an end portion of pitch control rod 550. Hub 512 may be comprised of a metallic or composite material. For example, metallic materials may include one or more of aluminum, titanium, or any other metal and / or alloys of one or more thereof. For example, composite materials may include one or more of fibers of fiberglass, carbon, steel, titanium, or alloys thereof in a binding plastic such as epoxy, polyester, vinyl ester, or nylon. Hub 512 may be configured to rotate at a blade rotational rate, where rotor drive system 540 is configured to drive the rotation of hub 512. In some embodiments, rotor drive system 540 may include gearbox 542. Gearbox 542 may be aligned along engine main shaft 558 to provide a gear reduction between engine main shaft 558 and bearing 552. Torque applied to engine main shaft 558 may be transferred to pitch control system 510 via flangeAgent Reference: 16498-0014-00304546. Flange 546 may be secured to hub 512, using bolts, screws, joints, rivets, welding, brazing, or any other method of attachment. In some embodiments, hub 512, yoke 522, ball nut 514, plurality of blade bearings 516, and / or plurality of blades 518 may be configured to receive the torque applied by the engine main shaft 558 and rotate at the rotational rate. In some embodiments, frame 562, first motor 566, planetary reducer 568, clutch mechanism 570, and / or feedback sensor 574 may be configured to rotate at the rotational rate of engine main shaft 558.

[0112] In some embodiments, pitch control system 510 may be configured to adjust the rotation of pitch control rod 550 relative to the rotation of engine main shaft 558. For example, as discussed with respect to Fig. 5B, pitch control rod 550 may be threaded into engine main shaft 558 such that the relative rotation results in linear translation of pitch control rod 550 relative to engine main shaft 558. Pitch control system 510 may thus be configured to cause a rotational motion of the plurality of blades 518 about their longitudinal axes to change the pitch angles of blades 518. In some embodiments, control unit 576 is operatively configured to control (e.g., manage, regulate, adjust, and / or monitor) the pitch angle of rotor blades 518 through coordinated actuation of a pitch control rod 250. Control unit 576 may be configured to receive a sensor signal from feedback sensors 564, 574. The sensor signal of feedback sensors 564, 574 may represent a torque, angular speed, and / or angular position of pitch control rod 550 and / or angular displacement, rotational velocity, and / or phase position of rotor 590 (see Fig. 5E). For example, control unit 576 may send a command signal to first motor 566 to operate at a speed, direction, or torque to achieve a desired pitch angle of blades 518.

[0113] For example, in some embodiments, first motor 566 may power the rotation of an output shaft of first motor 566. The output shaft of first motor 566 may be connected to a planetary reducer 568 (e.g., planetary gearbox) comprising one or more gears configured to rotate an output shaft of planetary reducer 568 at a lower rotational rate than the rotational speed of the output shaft of first motor 566. The output shaft of planetary reducer 568 may connect with a splined shaft or comprise a splined shaft end connected to pitch control rod 550. In some embodiments, the splined shaft end or splined shaft may be coupled to pitch control rod 550 such that there is no relative displacement between the splined shaft end or splined shaft and pitch control rod 550. In some embodiments, the splined shaft end or splined shaft may be connected (e.g., screwed, bolted, jointed) to a surface of pitch control rod 550 (e.g., radially inner surface of pitch control rod 550).Agent Reference: 16498-0014-00304

[0114] According to some embodiments, clutch mechanism 570 may comprise mechanical components configured to selectively engage and disengage the rotational input from a prime mover (e.g., 558) to a driven transmission shaft (e.g., output shaft 572). Clutch mechanism 570 may selectively engage and disengage the rotational input in order to adjust a pitch angle of blades 518. Clutch mechanism 570 may include an input mechanism (e.g., clutch pedal and / or digital input such as a monitor) operably connected via an actuating rod or cable to a release fork. The release fork may be pivotally mounted upon a fixed support structure within the housing and configured to exert axial displacement upon a release bearing, parallel to the longitudinal axis of pitch control rod 550. According to some embodiments, the release bearing interfaces with a diaphragm spring of the pressure plate assembly. Upon depression of the clutch pedal, the release bearing displaces the diaphragm spring radially inward, thereby retracting the pressure plate from the friction disc and interrupting torque transmission.

[0115] The friction disc, also referred to as the clutch disc, comprises a splined central hub engageable with the input shaft of a transmission. Said disc incorporates torsional dampening springs disposed circumferentially around the hub to absorb transient vibrations and impact forces upon engagement. The pressure plate assembly, comprised of a cover housing, diaphragm spring, and pressure surface, is configured to exert compressive force against the friction disc during operational engagement. When released, the pressure plate clamps the friction disc, thereby transmitting rotational motion to the input shaft through a mechanical coupling. Additional structural elements may include alignment dowels, retaining fasteners, and bearing guides, all cooperating to ensure axial stability and concentric operation of the system throughout its functional cycle.

[0116] Fig. 5B illustrates a portion of pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B. Fig. 5C illustrates a portion of pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B.

[0117] According to some embodiments, clutch mechanism 570 may comprise a base disc. Pitch control lock may comprise base disc, detents 582, springs 584, and disc 580. Pitch control rod lock may be configured to lock and unlock pitch control rod 550 to engine main shaft 558. Base disc may comprise the plurality of detents 582 and the plurality of springs 584 located therein. Base disc may be configured to be relatively stationary to pitch controlAgent Reference: 16498-0014-00304 rod 550 in an unlocked state. However, in a locked state, base disc may be coupled to disc 580 via detents 582 such that there is no relative displacement between base disc and disc 580.

[0118] According to some embodiments, clutch mechanism 570 may comprise one or more detents 582 and one or more springs 584. According to certain embodiments, each spring 584 may be configured to bias detents 582 in a direction parallel to the axial direction (e.g., parallel to the longitudinal axis of pitch control rod 550).

[0119] In some embodiments, pitch control rod lock may comprise a locked state. For example, a locked state may comprise a configuration in which each detent 582 is located within a respective indent of a plurality of indents located on a surface of disc 580. In some embodiments, the plurality of detents 582 may form a series of concentric circles on the surface of disc 580. In some embodiments, the locked state may be configured such that relative displacement between pitch control rod 550 and engine main shaft 558 is permitted. In some embodiments, pitch control rod 550 may accelerate or decelerate (e.g., rotationally) relative to engine main shaft 558 in the locked state.

[0120] In some embodiments, pitch control rod lock may comprise an unlocked state. For example, an unlocked state may comprise a configuration where no detent 582 is located within a respective indent of the plurality of indents of disc 580. In some embodiments, the unlocked state may be configured such that there is no relative displacement between pitch control rod 550 and engine main shaft 558 (i.e., they rotate together at the same rotational rate).

[0121] The rotational rate of pitch control rod 550 relative to the rotational rate of engine main shaft 558 may be described as a phase angle. In some embodiments, a predetermined phase angle between pitch control rod 550 and engine main shaft 558 is configured to linearly displace yoke 522 relative to pitch control rod 550 at a predetermined rate (e.g., parallel to longitudinal axis of pitch control rod 550). A linkage system may couple yoke 522 to blade bearings 516. The linkage system may comprise one or more arms and one or more slotted openings configured to translate a linear displacement of yoke 522 into rotation of blade bearings 516.

[0122] Fig. 5D illustrates a portion of pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B.Agent Reference: 16498-0014-00304

[0123] In some embodiments, first motor 566 may comprise an induction motor. In some embodiments, first motor 566 may be configured to increase or decrease the rotational rate of pitch control rod 550.

[0124] In some exemplary embodiments, encoder 586 comprises a helically threaded shaft operably configured to interface with rotational motion input from pitch control rod 550. Encoder 586 is structurally coupled with a rotational sensing assembly which comprises a first portion located on encoder 586 and a second portion located on an induction motor plate coupled to first motor 566 (e.g., sensors 564 may comprise the first and second portions). As the pitch control rod 550 rotates, encoder screw undergoes corresponding angular displacement, which is sensed by sensors 564 to generate positional output signals indicative of a rotational state of the pitch control rod 450 and a rotational state of yoke 522. Yoke 522 may be configured to rotate continuously, which results in a continuous adjusted pitch angle of blades 518. The threading geometry of encoder screw may further permit incremental displacement of a sensor-facing target surface (e.g., sensors 564) along the axial direction, enhancing positional resolution. Encoder screw may also be coupled with a yoke 522, wherein yoke’s 522 reciprocating linear motion is derived from rotational input, such as from engine main shaft 558. In this configuration, encoder screw is mounted coaxially or in mechanical communication with yoke’s 522 rotational element. As yoke 522 converts rotary input into linear stroke, encoder screw tracks the angular position of the pitch control rod 550 relative to its rotary origin. Proximity sensors 564 detect discrete positions of encoder screw via interruption or reflection of sensing signals, facilitating high-resolution feedback for adaptive pitch regulation, dynamic damping adjustment, or servo-controlled actuation.

[0125] Fig. 5E illustrates a portion of pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B.

[0126] In some embodiments, encoder 586 may be configured to monitor lobed wheel 578 at least partially surrounding pitch control rod 550. Lobed wheel 578 may be located on an end of an encoder screw. Lobed wheel 578 is disposed at a distal end of an encoder screw and concentrically surrounding pitch control rod 550. Lobed wheel 578 may be configured to rotate in synch with linear reciprocation of yoke 522. In other words, a rotation position of the lobed wheel 578 correlates with the linear position of yoke 522. Yoke 522 converts rotational motion of pitch control rod 550 into linear motion along an orthogonal axis, thereby inducing periodic rotation of lobed wheel 578 of an encoder screw of encoder 586.Agent Reference: 16498-0014-00304

[0127] In some embodiments, encoder 586 is positioned in proximity to the rotating lobed wheel and comprises a sensing array adapted to detect geometrical transitions of lobed wheel 578. Each rotational increment of lobed wheel 578 (e.g., derived from the linear oscillation of a scotch yoke 522) corresponds to a discrete angular event registered by encoder 586. Encoder 586 may utilize optical or magnetic sensing modalities to transduce lobed wheel 578 configurations into electrical signals for determining the rotational phase, velocity, and displacement of pitch control rod 550 and yoke 522.

[0128] In some embodiments, first motor 566 may comprise rotor 590 and stator 588. In some embodiments, rotor 590 and stator 588 are operatively disposed within frame 562 and are configured to produce torque about a shared central axis. The stator 588 comprises a plurality of electromagnetic coils embedded within and attached to frame 562. Rotor 590 may include ferromagnetic elements or permanent magnets circumferentially positioned to enable electromagnetic induction. Upon energization of stators 588, electromagnetic fields interact with rotor 590, inducing rotational motion via Lorentz force. Rotor 590 is mechanically linked to, for example, output shaft 572 or pitch control rod 550, thereby converting electromagnetic excitation into mechanical torque output. According to some embodiments, encoder 586 may be disposed (e.g., pointed and / or having a line of sight) toward rotor 590. Encoder 586 may comprise a signal transduction module configured to detect angular displacement, rotational velocity, and / or phase position of rotor 590.

[0129] Fig. 5F illustrates a portion of pitch control apparatus in a tilt apparatus 500 of a VTOL aircraft, consistent with embodiments of the present disclosure. The VTOL aircraft may be similar to, e.g., VTOL aircraft 100 of Figs. 1A-1B.

[0130] In some embodiments, bearing 552 at least partially surrounds pitch control rod 550, facilitating rotational support and minimizing or reducing frictional resistance during axial or torsional displacement of pitch control rod 550. Bearing 552 incorporates sensor 564 affixed to an external or internal surface thereof, wherein sensor 564 is configured to detect relative motion, vibrational states, or positional changes between pitch control rod 550 and its surrounding structural elements. Sensor 564 may be a proximity, strain, or inertial-type sensor adapted to generate output signals representative of operational conditions or alignment states.

[0131] Yoke shaft 594 is disposed concentrically around pitch control rod 550 and positioned in rotational or translational communication with bearing 552. Ring 592 further surrounds yoke shaft 594 and pitch control rod 550, functioning as a stabilization or coupling element. During operation, yoke shaft 594 responds to mechanical actuation (e.g., from yoke 522) orAgent Reference: 16498-0014-00304 torsional inputs (e.g., from pitch control rod 550) and bearing 552 maintains guided rotation of pitch control rod 550 while enabling sensor 564 to monitor relative displacement of ring 592 and / or yoke shaft 594. Ring 592 may further restrict off-axis motion or serve as a reference indexing surface for sensor 564, enabling feedback control.

[0132] In some embodiments, as shown in Figs. 5A-5F, first motor 566 is operational during pitch variation. When the pitch is not being actively varied, first motor 566 is available to act instead as a generator to power cooling fan 214. For example, when rotor 590 is locked in rotation with engine main shaft 558, it may induce a current in stator 588. The coils of stator 588 may be switchably coupled to both a power source for driving first motor 566, and to wiring (such as wiring 302 of Figs. 3A-B) for powering a cooling fan motor (such as cooling fan motor or second motor 307 of Figs. 3A-B).

[0133] A cooling fan (such as cooling fan 214 of Figs. 3A-B) may be electrically coupled to first motor 566, which may be configured to drive a pitch control rod, or another component of the aircraft other than the fan, in a first mode of operation (such as a pitch control mode of operation). In a second mode of operation (such as an engine cooling operation) first motor 566 may act as a generator to power a second motor configured to drive the cooling fan to drive an airflow and cool a propeller engine. In some embodiments, the operation of the cooling fan is interrupted when first motor 566 is in or switches to the first mode of operation in which first motor 566 drives another component of the aircraft, other than the fan, for example, the pitch control rod.

[0134] In some embodiments, first motor 566 may power actuation of pitch variation in the first mode of operation and cooling fan 214 in the second mode of operation (for example, via the second motor). In some embodiments, the cooling system may comprise a switch system configured to change the mode of operation of first motor 566 between the first mode of operation, e.g., pitch adjustment, and the second mode of operation, e.g., fan operation. For example, in the first mode of operation, coils in the stator 588 may receive current from a power source to rotate rotor 590. In this mode, the cooling fan motor may be electrically disconnected from first motor 566 by the switch system. In the second mode of operation, pitch control rod may be locked to a propeller shaft such that rotor 590 may be rotated by operation of the propeller shaft, and thus may induce a current in the coils of stator 588. In this mode of operation, stator 588 may be electrically disconnected from the power source by the switch system, and may be electrically connected to the cooling fan by the switch system. Therefore, the cooling fan may be powered by first motor 566 in the second mode ofAgent Reference: 16498-0014-00304 operation. The switch operation may be triggered by, e.g., activation of a command to start or stop operating first motor 566 in the first mode of operation.

[0135] Embodiments of the present disclosure may further be described by the following clauses:1. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a rotor coupled to the drive shaft; a stator adjacent to the rotor; and a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis, wherein rotation of the rotor with respect to the stator is configured to generate an electric current sent to the fan through at least one wire to cause the fan to rotate around the second axis, and wherein the fan is configured to drive an airflow from the inlet to the outlet.2. The cooling system of clause 1, wherein the outlet is located below the heat exchanger.3. The cooling system of clause 1 or 2, wherein the first axis and the second axis are parallel.4. The cooling system of clause 1 or 2, wherein the first axis and the second axis are not parallel.5. The cooling system of any one of clauses 1 to 4, wherein the rotor and the stator form a brushless DC motor.6. The cooling system of clause 5, wherein the brushless DC motor is configured to use a number of poles to control a rotation speed of the fan.7. The cooling system of any one of clauses 1 to 6, wherein the electric current passes through at least one resistor before reaching the fan.8. The cooling system of clause 7, wherein the at least one resistor comprises a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft.Agent Reference: 16498-0014-003049. The cooling system of clause 8, wherein the at least one resistor comprises a variable resistor configured to alter the electric current reaching the fan, causing the rotation speed of the fan to be different from or equal to the rotation speed of the drive shaft.10. The cooling system of any one of clauses 1 to 9, wherein the heat exchanger is affixed to a housing of the engine.11. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; and a fan belt coupled to the drive shaft and the fan, wherein the fan belt causes the fan to rotate around the second axis when the drive shaft rotates around the first axis; and wherein the fan is configured to drive an airflow from the inlet to the outlet.12. The cooling system of clause 11, wherein the outlet is located below the heat exchanger.13. The cooling system of clause 11 or 12, wherein the first axis and the second axis are parallel.14. The cooling system of clause 11 or 12, wherein the first axis and the second axis are not parallel.15. The cooling system of any one of clauses 11 to 14, wherein a rotation speed of the fan is equal to a rotation speed of the drive shaft.16. The cooling system of any one of clauses 11 to 14, wherein a rotation speed of the fan is different from a rotation speed of the drive shaft.17. The cooling system of any one of clauses 11 to 16, comprising a second fan belt coupled to a pulley and configured to change a rotation speed of the fan relative to a rotation speed of the drive shaft.18. The cooling system of any one of clauses 11 to 16, wherein the fan belt is further coupled to a gearbox to change a rotation speed of the fan relative to a rotation speed of the drive shaft.Agent Reference: 16498-0014-0030419. The cooling system of any one of clauses 11 to 18, wherein the heat exchanger is affixed to a housing of the engine.20. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; a first motor configured to drive a component of the aircraft other than the fan in a first mode of operation; and a second motor configured to drive the fan, wherein: the first motor is configured to power the second motor in a second mode of operation, and the fan is configured to drive an airflow from the inlet to the outlet.21. The cooling system of clause 20, wherein the component of the aircraft other than the fan is a pitch control apparatus.22. The cooling system of clause 20 or 21, wherein the first motor further comprises a rotor and a stator operably disposed in a frame, wherein the rotor and the stator are configured to produce torque about a shared central axis.23. The cooling system of clause 22, wherein the rotor comprises permanent magnets circumferentially positioned to enable electromagnetic induction.24. The cooling system of clause 22 or 23, wherein, upon energization of the stator, electromagnetic fields interact with the rotor to induce rotational motion of the rotor.25. The cooling system of any one of clauses 22 to 24, wherein the rotor is mechanically linked to a pitch control rod and configured to convert electromagnetic excitation of the rotor and the stator into mechanical torque output.26. The cooling system of any one of clauses 20 to 25, further comprising a pitch control rod, wherein the first motor is configured to engage the pitch control rod.Agent Reference: 16498-0014-0030427. The cooling system of any one of clauses 20 to 26, further comprising at least one resistor configured to receive electrical current from the first motor before the electrical current powers the fan.28. The cooling system of clause 27, wherein the at least one resistor comprises a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft.29. The cooling system of clause 27, wherein the at least one resistor comprises a variable resistor configured to alter the electric current reaching the fan, causing a rotation speed of the fan to be different from or equal to a rotation speed of the drive shaft.30. The cooling system of any one of clauses 20 to 29, further comprising a switch system configured to change operation of the first motor from the first mode of operation to the second mode of operation.31. The cooling system of any one of clauses 20 to 30, wherein the outlet is located below the heat exchanger.32. The cooling system of any one of clauses 20 to 31, wherein the heat exchanger is affixed to a housing of the engine.33. The cooling system of any one of clauses 20 to 32 wherein, the first motor is configured to power the second motor to drive the fan during take-off, landing, transition, or cruise stages of flight.34. The cooling system of any one of clauses 20 to 33, wherein the first motor is configured to power the second motor to drive the fan when the first motor is not in use for driving the component of the aircraft other than the fan.

[0136] The foregoing description has been presented for purposes of illustration. It 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 from consideration of the specification and practice of the disclosed embodiments of the inventions disclosed herein.

Claims

Agent Reference: 16498-0014-00304CLAIMS:

1. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a rotor coupled to the drive shaft; a stator adjacent to the rotor; and a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis, wherein rotation of the rotor with respect to the stator is configured to generate an electric current sent to the fan through at least one wire to cause the fan to rotate around the second axis, and wherein the fan is configured to drive an airflow from the inlet to the outlet.

2. The cooling system of claim 1, wherein the outlet is located below the heat exchanger.

3. The cooling system of claim 1 or 2, wherein the first axis and the second axis are parallel.

4. The cooling system of claim 1 or 2, wherein the first axis and the second axis are not parallel.

5. The cooling system of any one of claims 1 to 4, wherein the rotor and the stator form a brushless DC motor.

6. The cooling system of claim 5, wherein the brushless DC motor is configured to use a number of poles to control a rotation speed of the fan.

7. The cooling system of any one of claims 1 to 6, wherein the electric current passes through at least one resistor before reaching the fan.

8. The cooling system of claim 7, wherein the at least one resistor comprises a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft.

9. The cooling system of claim 8, wherein the at least one resistor comprises a variable resistor configured to alter the electric current reaching the fan, causing the rotation speed of the fan to be different from or equal to the rotation speed of the drive shaft.

10. The cooling system of any one of claims 1 to 9, wherein the heat exchanger is affixed to a housing of the engine.Agent Reference: 16498-0014-0030411. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft; an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; and a fan belt coupled to the drive shaft and the fan, wherein the fan belt causes the fan to rotate around the second axis when the drive shaft rotates around the first axis; and wherein the fan is configured to drive an airflow from the inlet to the outlet.

12. The cooling system of claim 11, wherein the outlet is located below the heat exchanger.

13. The cooling system of claim 11 or 12, wherein the first axis and the second axis are parallel.

14. The cooling system of claim 11 or 12, wherein the first axis and the second axis are not parallel.

15. The cooling system of any one of claims 11 to 14, wherein a rotation speed of the fan is equal to a rotation speed of the drive shaft.

16. The cooling system of any one of claims 11 to 14, wherein a rotation speed of the fan is different from a rotation speed of the drive shaft.

17. The cooling system of any one of claims 11 to 16, comprising a second fan belt coupled to a pulley and configured to change a rotation speed of the fan relative to a rotation speed of the drive shaft.

18. The cooling system of any one of claims 11 to 16, wherein the fan belt is further coupled to a gearbox to change a rotation speed of the fan relative to a rotation speed of the drive shaft.

19. The cooling system of any one of claims 11 to 18, wherein the heat exchanger is affixed to a housing of the engine.

20. A cooling system for an aircraft, the cooling system comprising: an air duct in the aircraft, the air duct comprising an inlet and an outlet; a drive shaft configured to rotate around a first axis and drive a propeller in the aircraft;Agent Reference: 16498-0014-00304 an engine configured to rotate the drive shaft; a heat exchanger thermally coupled to the engine and mechanically coupled to the air duct; a fan located in the air duct and configured to rotate around a second axis, the second axis being noncollinear with the first axis; a first motor configured to drive a component of the aircraft other than the fan in a first mode of operation; and a second motor configured to drive the fan, wherein: the first motor is configured to power the second motor in a second mode of operation, and the fan is configured to drive an airflow from the inlet to the outlet.

21. The cooling system of claim 20, wherein the component of the aircraft other than the fan is a pitch control apparatus.

22. The cooling system of claim 20 or 21, wherein the first motor further comprises a rotor and a stator operably disposed in a frame, wherein the rotor and the stator are configured to produce torque about a shared central axis.

23. The cooling system of claim 22, wherein the rotor comprises permanent magnets circumferentially positioned to enable electromagnetic induction.

24. The cooling system of claim 22 or 23, wherein, upon energization of the stator, electromagnetic fields interact with the rotor to induce rotational motion of the rotor.

25. The cooling system of any one of claims 22 to 24, wherein the rotor is mechanically linked to a pitch control rod and configured to convert electromagnetic excitation of the rotor and the stator into mechanical torque output.

26. The cooling system of any one of claims 20 to 25, further comprising a pitch control rod, wherein the first motor is configured to engage the pitch control rod.

27. The cooling system of any one of claims 20 to 26, further comprising at least one resistor configured to receive electrical current from the first motor before the electrical current powers the fan.

28. The cooling system of claim 27, wherein the at least one resistor comprises a static resistor configured to reduce the electric current reaching the fan, causing a rotation speed of the fan to be different from a rotation speed of the drive shaft.Agent Reference: 16498-0014-0030429. The cooling system of claim 27, wherein the at least one resistor comprises a variable resistor configured to alter the electric current reaching the fan, causing a rotation speed of the fan to be different from or equal to a rotation speed of the drive shaft.

30. The cooling system of any one of claims 20 to 29, further comprising a switch system configured to change operation of the first motor between the first mode of operation and the second mode of operation.

31. The cooling system of any one of claims 20 to 30, wherein the outlet is located below the heat exchanger.

32. The cooling system of any one of claims 20 to 31, wherein the heat exchanger is affixed to a housing of the engine.

33. The cooling system of any one of claims 20 to 32 wherein, the first motor is configured to power the second motor to drive the fan during take-off, landing, transition, or cruise stages of flight.

34. The cooling system of any of claims 20 to 33, wherein the first motor is configured to power the second motor to drive the fan when the first motor is not in use for driving the component of the aircraft other than the fan.

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