Vtol aircraft fan tilt mechanism and arrangement

Abstract

To provide an improved aircraft design which is safe and reliable and reduces weight and cost.SOLUTION: An aircraft comprising a fuselage, at least one wing coupled to the fuselage, a plurality of support elements coupled beneath the at least one wing, and a plurality of inclined fans. The plurality of inclined fans are each coupled to a support element of the plurality of support elements via a tilt mechanism and are configured to move between a vertical lift position and a forward flight position, wherein a first group of the inclined fans is configured to move to the vertical lift position upon a failure affecting functionality of one or more inclined fans of the first group.SELECTED DRAWING: Figure 5B

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 106,197, filed October 27, 2020, entitled "VTOL AIRCRAFT FAN TILTING MECHANISMS AND ARRANGEMENTS," the disclosure of which is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] Vertical take-off and landing (VTOL) aircraft are generally capable of generating vertical thrust, enabling a vertical, or primarily vertical, direction of travel. Such vertical take-off, landing, and hovering capabilities can enable the aircraft to land and take off without the spatial limitations of a runway or other space that enable traditional horizontal landings (such as airplanes). To provide this functionality, VTOL aircraft may have a vertical movement mechanism, such as a fan, that provides vertical thrust.

[0003] However, it is generally desirable for a VTOL aircraft to additionally be able to transition to horizontal thrust, and therefore horizontal movement, when the aircraft is not taking off, landing, or hovering so that the VTOL aircraft can "cruise" through the air. Thus, a VTOL aircraft may have separate movement mechanisms dedicated to providing vertical and horizontal thrust, respectively. A VTOL aircraft may have movement mechanisms that provide both directions of thrust.

[0004] Generally, in aircraft design, a major factor in an aircraft's capability depends on limiting the aircraft's weight. Limiting the number of components and their associated weight can allow for more energy-efficient flight, a larger payload, or a combination of both desired results.

[0005] As explained, while limiting weight with fewer components is desirable, this design configuration is tempered by inherent safety risks of flight. In particular, limiting the number of components in the power system can provide a design with weight advantages, but it also limits the power system's redundancy capabilities, increasing the risk of a single-fault failure, which could result in an accident due to aircraft failure in flight.

[0006] In general, it would be advantageous to provide an improved aircraft design that allows for weight and cost savings while providing beneficial safety and redundant design features to maintain a safe and reliable aircraft. Summary of the Invention

[0007] The described embodiments relate generally to aircraft having vertical takeoff and landing capabilities. In particular, the embodiments provide the aircraft with one or more inclined fans that provide vertical and horizontal thrust in a controlled manner for hovering, transition, and cruise (horizontal) flight.

[0008] Embodiments generally provide improved devices, systems, and methods for aircraft with multiple inclined fans. More specifically, the technology disclosed herein provides a VTOL aircraft (e.g., an electric VTOL aircraft) with multiple inclined fans that can be tilted between a horizontal position for vertical lift movement and a vertical position for forward flight movement. Various structures and configurations are provided that can enable various inclined fan operation and control, and can further provide, for example, a means of design efficiency, cost reduction, safety, and improved flight comfort and performance.

[0009] In some embodiments, a VTOL aircraft (hereinafter "aircraft") may be powered by various power units. For example, in various embodiments, the aircraft may have at least one power source that provides energy to various components of the aircraft. For example, the aircraft may be powered by one or more batteries, etc. The power mechanism may provide electrical power to one or more motors, actuators, or other power aspects of the aircraft.

[0010] According to various embodiments, an aircraft may include a fuselage. The fuselage may constitute a center body of the aircraft. In various embodiments, the fuselage may provide various layouts to provide a cockpit, a passenger cabin, and / or a storage area. Accordingly, the fuselage may have one or more bulkheads dividing various sections of the fuselage. The fuselage may further include one or more doors that allow access to the interior of the fuselage. For example, the fuselage may have one or more overhead doors, side doors, front doors, or rear doors. Various door configurations are contemplated that allow convenient access to the fuselage of the aircraft.

[0011] In some embodiments, the aircraft may include at least one wing attached to the fuselage. For example, the aircraft may have a left wing and a right wing coupled to each side of the fuselage. In various embodiments, the aircraft may have one or more wings spanning the width of the aircraft, such as extending across the fuselage and coupled to the top or bottom of the fuselage. Various wing configurations that provide desired aerodynamic advantages and / or allow for convenient ingress and egress of the aircraft are contemplated.

[0012] According to various embodiments, an aircraft may include one or more support elements (e.g., booms) that can be coupled to the top or bottom of a wing. In various embodiments, the one or more support elements may have a generally tubular structure and extend laterally from at least one wing. For example, the support elements may extend toward the front and rear of the aircraft to distribute or space various fans (or other mechanisms providing thrust) for purposes such as aircraft balance and thrust distribution. In various embodiments, the fans may be attached to the support elements at both ends, such that a front fan may be located at the leading edge of the wing and a rear fan may be located at the trailing edge of the wing. In various embodiments, the support elements may be hollow and thus house various elements of the aircraft, particularly elements of the aircraft's control system.

[0013] In some embodiments, the aircraft may include multiple fans. The multiple fans may include fixed fans, which provide thrust in a single direction. The multiple fans may include tilting fans, which can rotate or pivot to provide thrust in various directions. For example, the tilting fans may be movable between a vertical lift position and a forward flight position. Furthermore, the tilting fans can provide thrust in various directions between the vertical lift position and the forward flight position, thereby enabling partially vertical flight, partially horizontal flight, or providing maneuvering capabilities for the aircraft. According to various embodiments, the tilting fans and the fixed fans may include variable pitch mechanisms to provide adjustment of the pitch of each fan's blades depending on flight direction and speed. The variable pitch mechanism may include an actuator that twists the blades about a blade axis.

[0014] In some embodiments, the aircraft may include multiple tilt mechanisms that can be coupled to at least one tilt fan. The multiple tilt mechanisms can act to rotate or pivot the multiple fans between a vertical lift position and a horizontal flight position. The multiple tilt mechanisms can include various structures and components to provide this functionality, including, for example, motors, hydraulic pistons (with hydraulic lines), and / or coupling mechanisms (e.g., linkage arms). The multiple tilt mechanisms may be provided within a given support element.

[0015] According to various embodiments, the aircraft may include an actuator (or multiple actuators). The actuator may be coupled to one or more of the multiple tilt mechanisms, for example, via a control arm (and / or drive shaft) or via a hydraulic line. For example, the actuator may act to actuate one or more of the multiple tilt mechanisms. According to various embodiments, the actuators described herein that may drive the movement of the tilt mechanisms may include, among other components, a rotary electric motor (with or without a gearbox), a linear direct drive electric motor, a ball screw actuator (e.g., a rotary electric motor with a ball screw transmission for obtaining linear motion), a compressor, a hydraulic piston, or a pneumatic piston.

[0016] In some embodiments, the aircraft control system may be designed according to a coupling scheme. The coupling scheme may provide a specific configuration by which multiple tilt fans are connected to each other. Various examples of embodiments are provided herein for controlling the tilt aspects of the tilt fans, such that various tilt fans may be coupled by a tilt mechanism, for example, such that a given number of multiple tilt fans operatively tilt in coordination with each other.

[0017] Various embodiments are disclosed in the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1A]FIG. 1 illustrates a simplified diagram of an exemplary VTOL aircraft including a tilt fan in a forward flight position, in accordance with various embodiments. [Figure 1B] FIG. 1 illustrates a simplified diagram of an exemplary VTOL aircraft including an inclined fan in an exemplary vertical lift position, in accordance with various embodiments. [Figure 2A] 1 illustrates an exemplary VTOL aircraft including tilt fans coupled in pairs to support elements, according to various embodiments. [Figure 2B] 1 illustrates another exemplary VTOL aircraft including tilt fans coupled in pairs to support elements in accordance with various embodiments. [Figure 3A] 1 illustrates an exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, according to various embodiments. [Figure 3B] 1 illustrates another exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, in accordance with various embodiments. [Figure 3C] 1 illustrates yet another exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, in accordance with various embodiments. [Figure 4A] 1 illustrates an exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, according to various embodiments. [Figure 4B] 1 illustrates another exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, in accordance with various embodiments. [Figure 4C] 1 illustrates yet another exemplary control system for a VTOL aircraft for providing swirl or tilt of multiple tilt fans, in accordance with various embodiments. [Figure 5A] 1 illustrates an exemplary embodiment in which a front inclined fan and a rear inclined fan are coupled to a support element, according to various embodiments. [Figure 5B] 1 illustrates the positions of the front and rear tilt fans during inbound (e.g., flight to landing) and outbound (e.g., stationary to flight) transitions of a VTOL aircraft, according to various embodiments. [Figure 6A]1 illustrates an aft tilting fan tilting from a vertical flight position to a forward flight position according to various embodiments. [Figure 6B] 1 illustrates another rear tilting fan tilting from a vertical flight position to a forward flight position according to various embodiments. [Figure 6C] 10 illustrates yet another rear-tilting fan tilting from a vertical flight position to a forward flight position in accordance with various embodiments. [Figure 6D] 1 illustrates blade folding of an aft-tilt fan according to various embodiments. [Figure 6E] 10 illustrates another folding of the blades of the rear-tilt fan according to various embodiments. [Figure 6F] 10 illustrates yet another folding of the blades of the rear-inclined fan according to various embodiments. [Figure 7A] 1 illustrates an exemplary control system including an exemplary tilt mechanism for a front tilt fan, according to various embodiments. [Figure 7B] 1 illustrates another exemplary control system including an exemplary tilt mechanism for a front tilt fan, according to various embodiments. [Figure 7C] 1 illustrates yet another exemplary control system including an exemplary tilt mechanism for a front tilt fan, according to various embodiments. [Figure 8A] 1 illustrates an exemplary control system including exemplary tilt mechanisms for a front tilt fan and a rear tilt fan, according to various embodiments. [Figure 8B] 1 illustrates another exemplary control system including exemplary tilt mechanisms for front and rear tilt fans, according to various embodiments. [Figure 8C] 1 illustrates yet another exemplary control system including exemplary tilt mechanisms for front and rear tilt fans, according to various embodiments. [Figure 8-1A] 8B illustrates the control system of FIG. 8A including a drive shaft mounted on a wing, according to various embodiments. [Figure 8-1B] 8C illustrates the control system of FIG. 8B including a drive shaft mounted on the wing, according to various embodiments. [Figure 8-1C]8D illustrates the control system of FIG. 8C including a drive shaft mounted on the wing, according to various embodiments. [Figure 9] 1 illustrates an embodiment in which one driver (e.g., compressor, valve, or primary piston) drives two tilt mechanisms coupled to respective paired tilt fans based on a fault condition, according to various embodiments. [Figure 10] 1 illustrates a single actuator driving multiple primary cylinders, according to various embodiments. [Figure 11] 1 illustrates an exemplary control system including two actuators, each driving multiple primary cylinders, according to various embodiments. [Figure 12A] FIG. 1 illustrates a cross-sectional view of an exemplary primary cylinder system pressurized by a single ball screw actuator, according to various embodiments. [Figure 12B] 1 illustrates a cross-sectional view of an exemplary primary cylinder system for incorporating two redundant pistons within a single primary cylinder, according to various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0019] The technology disclosed herein generally relates to aircraft having multiple tilting fans (e.g., propellers). More specifically, the technology disclosed herein provides a VTOL aircraft having multiple tilting fans that can be tilted between a horizontal position for vertical lift movement and a vertical position for forward flight movement. Various embodiments of the invention are described herein, including methods, processes, systems, devices, and the like.

[0020] To better understand the features and aspects of the control systems and power supply configurations for aircraft according to the present disclosure, further context for the present disclosure is provided in the following sections by describing specific embodiments of VTOL aircraft according to embodiments of the present disclosure. These embodiments are for illustrative purposes only, and other configurations may be employed in connection with the VTOL aircraft described herein.

[0021] 1A-1B show simplified diagrams of an exemplary VTOL aircraft 100. FIG. 1A shows the exemplary VTOL aircraft with the inclined fans 102, 104 in a forward flight position. FIG. 1B shows the exemplary VTOL aircraft 100 with the inclined fans 102, 104 in a vertical flight position. According to various embodiments, the VTOL aircraft 100 may be an electrically powered aircraft (e.g., an electric aircraft). In some embodiments, the VTOL aircraft 100 may be configured to carry one or more passengers and / or cargo and may be controlled automatically and / or remotely (e.g., may not require an onboard pilot to operate the aircraft). In the illustrated example, the VTOL aircraft 100 includes a fuselage 110, which may include a cabin section for carrying passengers and / or cargo.

[0022] VTOL aircraft 100 may include at least one wing 108 attached to fuselage 110. For example, the aircraft may have a left wing and a right wing coupled to each side of fuselage 110. In various embodiments, VTOL aircraft 100 may have one or more wings spanning the width of VTOL aircraft 100, such as extending across fuselage 110 and coupled to the top or bottom of fuselage 110.

[0023] One or more support elements 106 (or "booms") may be coupled to wings 108 of the VTOL aircraft 100. For example, the wings 108 may include left and right wings. Each of the left and right wings may include three support elements 106. For example, the support elements 106 may be elongated in shape extending perpendicularly from the wings 108, with a front portion and a rear portion.

[0024] In various embodiments, the VTOL aircraft 100 may include multiple inclined fans 102, 104. For example, the VTOL aircraft may have a forward inclined fan 102 and an aft inclined fan 104. In various embodiments, the multiple inclined fans 102, 104 may be coupled to one or more wings 108 and / or to one or more support elements 106. For example, each support element may include a pair of inclined fans 102, 104 mounted thereon. The inclined fans 102, 104 of the VTOL aircraft 100 may include propulsion motors that power the fans of the inclined fans 102, 104. The inclined aspect of the inclined fans may enable the inclined fans to provide thrust from the propulsion motors in various directions, enabling variable pitch for both vertical and horizontal propulsion, as well as for steering and control of the VTOL aircraft 100, etc.

[0025] The VTOL aircraft 100 may also include a combination of tilt fans 102, 104 and fixed fans, such that the fixed fans provide thrust in a single direction (e.g., vertically only or horizontally only). According to various embodiments, the tilt fans and fixed fans may include variable pitch mechanisms to provide adjustment of the pitch of each fan's blades depending on flight direction and speed. The variable pitch mechanism may include an actuator that twists the blades about a blade axis. A tilt mechanism may be coupled to the pitch of the tilt fan's blades.

[0026] 2A-2B illustrate an exemplary VTOL aircraft 100 including a right wing 206 and a left wing 208, respectively, coupled to the fuselage 110 of the VTOL aircraft 100. At least one wing of the VTOL aircraft 100 includes a right wing 206 portion and a left wing 208 portion. In the exemplary embodiment shown in FIGS. 2A-2B, the VTOL aircraft 100 further includes six support elements 106 and twelve inclined fans coupled in pairs to the six support elements 106. As shown in FIGS. 2A-2B, three support elements 106 are coupled to each wing 206, 208 of the VTOL aircraft 100. For ease of reference, the inclined fans may be numbered as shown. The forward inclined fans 102 may be numbered 1 through 6, and the aft inclined fans 104 may be numbered 7 through 12.

[0027] The tilting fans 1-12 can be switched (e.g., rotated or tilted) between a forward flight position (shown in FIG. 2A) and a vertical flight position (shown in FIG. 2B). That is, FIG. 2A shows the tilting fans 1-12 (e.g., the tilting fan blades) in a vertical position for forward motion. FIG. 2B shows the tilting fans 1-12 (e.g., the tilting fan blades) in a horizontal position for vertical flight (e.g., for moving the aircraft vertically during takeoff, hovering, and / or landing). In the implementation shown in FIGS. 2A-2B, all of the tilting fans 1-12 are attached to the respective support elements 106 in fixed positions relative to the wings 206, 208. The tilting fans 1-12 may be coupled to the support elements 106 via one or more tilting mechanisms, including, for example, motors, hydraulic systems, and / or coupling mechanisms. According to various embodiments, each of the tilting fans 1-12 may be equipped with a respective tilting mechanism.

[0028] Those skilled in the art will appreciate that the number and location of the tilt fans are not limited to those shown in Figures 2A-2B, and that the VTOL aircraft 100 may include fewer or more tilt fans located on the wings or other locations on the individual support elements 106.

[0029] According to various embodiments, VTOL air vehicle 100 may further include one or more fixed fans that provide thrust in only one direction (e.g., vertical lift or horizontal flight). For example, in various embodiments, one or more of the multiple fans on each support element 106 may be fixed fans that are fixed in a vertical lift position or a forward flight position during operation.

[0030] 3A-3C illustrate an exemplary control system 300 for providing pivoting or tilting of tilt fans 302, 304 of VTOL aircraft 100. For example, control system 300 may include a tilt mechanism 306. In various embodiments, tilt mechanism 306 may be coupled to or provided within (e.g., housed or embedded in) support element 308. Forward tilt fan 302 and aft tilt fan 304 may be coupled to opposite ends of support element 308. Support element 308 may be provided, for example, under wing 310 and coupled to wing 310 or the fuselage of VTOL aircraft 100.

[0031] The tilt mechanism 306 can be operatively coupled to the forward-inclined fan 302 and the rear-inclined fan 304. Thus, the tilt mechanism 306 can simultaneously control the forward-inclined fan 302 and the rear-inclined fan 304. As shown in FIGS. 3A-3C , the tilt mechanism 306 can be a mechanical mechanism that can move from a first position to a second position. For example, the tilt mechanism can include a drive shaft 314 that pushes one or more elongated elements (e.g., bars) 316 horizontally or in a horizontal direction. The drive shaft 314 can be disposed within the support element 308.

[0032] In FIG. 3A , tilt mechanism 306 may be in a first position with tilt fans 302, 304 in a vertical lift position, providing vertical thrust. Specifically, drive shaft 314 is angled toward the front of VTOL aircraft 100. As tilt mechanism 306 moves toward a second position, as shown in FIG. 3B , tilt fans 302, 304 may transition toward a forward flight position. Specifically, drive shaft 314 is angled vertically such that elongated element 316 is pushed rearward, orienting tilt fans 302, 304 in a horizontal position.

[0033] 3C, the tilt mechanism 306 has reached a second position such that the tilt fans 302, 304 are fully transitioned to their forward flight position and thrust can be applied horizontally. In the second position, the drive shaft 314 is angled aft, directing the tilt fans 302, 304 into their forward flight position.

[0034] In the vertical lift position, forward tilt fan 302 may be positioned above and above support element 308. Conversely, aft tilt fan 304 may face below and below support element 308 in the vertical lift position. When tilt mechanism 306 is in a second position, such that the tilt fans are in a forward flight position, forward tilt fan 302 may face forward toward the front of VTOL air vehicle 100, and aft tilt fan 304 may face aft toward the rear of VTOL air vehicle 100. In this manner, by reversing the orientation of tilt fans 302, 304 relative to each other, a single movement of actuating tilt mechanism 306 can result in simultaneous tilt of both tilt fans 302, 304.

[0035] According to some embodiments, both the forward inclined fan 302 and the aft inclined fan 304 may be positioned on the same side (e.g., upper / upward or lower / downward) of the support element 308 in the vertical lift position. According to some embodiments, both the forward inclined fan 302 and the aft inclined fan 304 may face on the same side (e.g., forward / forward or aft / backward) of the support element 308 in the forward flight position.

[0036] In some embodiments, the control system 300 of the VTOL aircraft 100 may further include an actuator 312. The actuator 312 may be operatively coupled to the tilt fans 302, 304 via the tilt mechanism 306. Specifically, as shown, a drive shaft 314 couples the actuator 312 to the bar 316. In this manner, the actuator 312 may act to change the angle of the drive shaft 314, thereby moving the bar 316. For example, the actuator 312 may be a motor or other power system that moves the tilt mechanism 306 from a first position to a second position. As shown in FIG. 3A , the actuator 312 is provided (e.g., housed or embedded) within the support element 308. Such a configuration may allow the actuator 312 to be closer to the bar 316 so that the drive shaft 314 is shorter, e.g., reducing weight.

[0037] According to various embodiments, the actuators described herein that can drive the movement of the tilt mechanism may include, among other components, a rotary electric motor (with or without a gearbox), a linear direct drive electric motor, a ball screw actuator (e.g., a rotary electric motor with a ball screw transmission to obtain linear motion), a hydraulic piston, or a pneumatic piston.

[0038] 3A-3C has the advantage of including half the number of actuators compared to having a first actuator on the rear tilt fan 304 and a second actuator on the front tilt fan 302. This configuration increases the reliability of the design by reducing the number of parts (e.g., actuators) that can fail, as well as reducing the weight and power loss of having two separate actuators (i.e., one for each tilt fan 302, 304).

[0039] 4A-4C illustrate an exemplary control system 400 for providing pivoting or tilting of tilt fans 402, 404 of VTOL air vehicle 100. For example, control system 400 may include a tilt mechanism 406. In various embodiments, tilt mechanism 406 may be coupled to or provided within (e.g., housed or embedded in) support element 408. Forward tilt fan 402 and aft tilt fan 404 may be coupled to opposite ends of support element 408. Support element 408 may be provided, for example, under wing 410 and coupled to wing 410 or the fuselage of VTOL air vehicle 100.

[0040] The tilt mechanism 406 can be operatively coupled to the forward tilt fan 402 and the aft tilt fan 404. As shown in FIGS. 4A-4C , the tilt mechanism 406 can include a mechanical system capable of moving from a first position to a second position. For example, the tilt mechanism 406 can include a drive shaft 414 that pushes one or more elongated elements (e.g., bars) 416 horizontally. The drive shaft 414 can be at least partially disposed within the wing 410.

[0041] In FIG. 4A , the tilt mechanism 406 may be in a first position with the tilt fans 402, 404 in a vertical lift position, providing vertical thrust. Specifically, the drive shaft 414 is angled toward the front of the VTOL aircraft 100. As the tilt mechanism 406 moves toward a second position, as shown in FIG. 4B , the tilt fans 402, 404 may transition toward a forward flight position. Specifically, the drive shaft 414 is angled vertically such that the bar 416 is pushed rearward, directing the tilt fans 402, 404 toward the forward flight position.

[0042] 4C, the tilt mechanism 406 has reached a second position such that the tilt fans 402, 404 are fully transitioned to a forward flight position and thrust can be applied horizontally. In the second position, the drive shaft 414 is angled rearward, pointing the tilt fans 402, 404 horizontally.

[0043] In the vertical lift position, forward tilt fan 402 may be positioned above and above support element 408. Conversely, aft tilt fan 404 may face below and below support element 408 in the vertical lift position. When tilt mechanism 406 is in a second position, such that the tilt fans are in a forward flight position, forward tilt fan 402 may face forward toward the front of VTOL air vehicle 100, and aft tilt fan 404 may face aft toward the rear of VTOL air vehicle 100. In this manner, by reversing the orientation of tilt fans 402, 404 relative to each other, a single movement of actuating tilt mechanism 406 can result in simultaneous rotation of both tilt fans 402, 404.

[0044] In various embodiments, the control system 400 of the VTOL aircraft 100 may further include an actuator 412. The actuator 412 may be operatively coupled to the tilt fans 402, 404 via the tilt mechanism 406. Specifically, as shown, a drive shaft 414 couples the actuator 412 to an elongated element (e.g., a bar) 416 of the tilt mechanism 406. In this manner, the actuator 412 may act to change the angle of the drive shaft 414, thereby moving the bar 416. For example, the actuator 412 may be a motor or other power system that moves the tilt mechanism 406 from a first position to a second position. As shown in FIG. 4A , the actuator 412 is disposed within the wing 410. Such a configuration may allow the actuator 412 to be further away from the bar 416 so that additional torque can be applied to the bar 416. Furthermore, the embodiment shown in FIGS. 4A-4C allows the rotational axis of the tilt fans 402, 404 to be provided on the wing 410.

[0045] According to various embodiments, drive shafts 414 interconnect multiple tilt fans such that actuators 412 drive the tilt of all tilt fans (individually, in subsets, or all together) of the VTOL aircraft 100. In the exemplary embodiment shown in FIGS. 4A-4C , all tilt fans 402, 404 coupled to the same wing 410 may be controlled using a single drive shaft 414, such as one that penetrates the wing 410. For example, the drive shaft 414 may penetrate the horizontal center of the wing 410. Such an exemplary system may have improved reliability compared to having independent actuators (one actuator for each tilt fan).

[0046] While FIGS. 4A-4C illustrate VTOL aircraft 100 as having a forward inclined fan 402 and an aft inclined fan 404, it will be understood from a three-dimensional perspective that VTOL aircraft 100 may have several support elements 408, each with multiple inclined fans. In this manner, forward inclined fan 402 and aft inclined fan 404 on one support element may be connected via a single tilt mechanism 406 and arranged with a single actuator 412. Furthermore, other inclined fans coupled to other support elements 408 or other wings 410 may be connected to the same tilt mechanism 406 and / or arranged with the same actuator 412. For example, right wing 206 may have three forward inclined fans (4, 5, 6) and three aft inclined fans (10, 11, 12), all controlled by a single control system 400 including a single actuator 312. A similar configuration may be used for the multiple fans coupled to left wing 208. In various embodiments, each of the multiple tilt fans on each of wings 206, 208 may be controlled by a separate control system 400 or may share various components, including actuators 412. Alternatively, a predetermined number of tilt fans may be grouped together (e.g., tilt fans coupled to a given wing, a given support element, a forward tilt fan, or any other configuration) and controlled using a single actuator. According to yet other embodiments, different drive shafts may extend through the wing to actuate different tilt fans. According to yet other embodiments, VTOL aircraft 100 may include fixed fans in addition to tilt fans 402, 404.

[0047] The actuator size required to tilt a single fan is related at least in part to the gyroscopic torque applied to the tilt mechanism due to gyroscopic reaction torque from aircraft attitude changes. The gyroscopic torque equation is: Gyro_torque=cross_product(omega_airplane,J*omega_fan) where gyro_torque, omega_airplane, and omega_fan are all vector quantities. Omega_airplane is the time rate of change of the aircraft's attitude, and omega_fan is the speed at which the fan spins to provide thrust. The J variable is the polar moment of inertia of the fan.

[0048] For airplanes with multiple fans, omega_airplane is the same for all fans because they are all connected to the same relatively rigid airframe. In some embodiments, all fans may have the same polar moment of inertia. Some fans may spin clockwise, while other fans may spin counterclockwise. In some embodiments, the number of fans spinning clockwise may equal the number of fans spinning counterclockwise. In some embodiments, all of the fans may spin at the same speed (e.g., the magnitude of omega_fan is the same for all fans, but the sign may be positive or negative).

[0049] In some embodiments in which multiple fans are tilted using a single actuator, the mechanism may be designed so that all of the fans' spin axes are approximately parallel. The embodiments shown in Figures 3A-3C, 4A-4C, and 8A-8C are examples of this type of mechanism. When there are two fans interconnected in this manner, it is possible to have one spin clockwise and the other spin counterclockwise. This configuration has the benefit of causing the gyroscopic torque of one fan to cancel out the gyroscopic torque of the other fan (called the "cancellation effect"), thus reducing the size of the actuator that must be used to provide the tilting motion. Reduced-size actuators are lighter, which is a major benefit in aircraft design. In further embodiments with an even number of fans connected to a single mechanism, a cancellation effect may be achieved when one half of the fans spins in one direction and the other half spins in the other direction.

[0050] In some embodiments, tilt fans may be paired based on a failure condition. According to various embodiments, if one of the fans fails, it is preferable to shut down the corresponding fan to equalize (balance) the failure and keep the aircraft balanced (or near-balanced). The corresponding fan may be diametrically symmetrical to the failing fan about the aircraft's center of gravity. For example, referring back to FIG. 2A , fan number 8 may be paired with fan number 5. Fan number 8 is diametrically symmetrical to fan number 5 about the aircraft's center of gravity. If fan numbers 5 and 8 fail together, there is no impact on VTOL aircraft 100, and the remaining fan keeps the aircraft balanced. Thus, tilt fans paired based on a failure condition may be connected to the same tilt mechanism. For example, tilt fans may be connected to a drive shaft in a wing and coupled to the same actuator. Thus, instead of having tilt fans on the same support element coupled to the same actuator (as shown in FIGS. 3A-3C ), tilt fans paired based on a failure condition may be coupled to the same actuator in FIGS. 4A-4C . The exemplary embodiment shown in Figures 4A-4C includes half the number of actuators as the embodiment in which each tilt fan has its own actuator, but provides the same level of safety as the embodiment in which each tilt fan has its own actuator.

[0051] FIG. 5A illustrates an exemplary embodiment of a VTOL aircraft 500 in which a forward inclined fan 502 and an aft inclined fan 504 are coupled to a support element 506. The support element 506 may be provided under a wing 510 and / or coupled to the wing 510 or the fuselage of the VTOL aircraft. The aft inclined fan 504 is used during forward flight and has a variable pitch. The forward inclined fan 502 may include, for example, two, three, four, or five blades. In an exemplary embodiment, the aft inclined fan 504 may provide thrust only in vertical flight mode, may not have variable pitch, and may be optimized for vertical flight. In forward flight, the aft fan 504 may not be utilized and thus provides little or no thrust. The aft inclined fan 504 may include, for example, two, three, four, or five blades. In forward flight, the aft inclined fan 504 may either freewheel or fold to reduce drag. Aft fan 504 may be rotatably coupled to the aft end of support element 506 via any suitable coupling means, such as arm 508. One or more travel-limiting stops 516 may be coupled to the aft end of support element 506 closer to aft inclined fan 504. Travel-limiting stops 516 may act to limit the angle of rotation of arm 508, and therefore aft inclined fan 504. For example, arm 508 may only rotate between a vertical orientation (such that aft inclined fan 504 is positioned directly below the support element / wing / fuselage) and a horizontal orientation (such that aft inclined fan 504 points directly behind the support element / wing / fuselage).

[0052] In some embodiments, a spring element 512 may hold the arm 508 against one of the travel-limiting stops 516. Similar to a spring-loaded hinge, the spring element 512 may act to provide a preload on the arm 508 so that the force required to tilt the rear tilt fan 504 from a vertical lift position to a forward flight position may be reduced by the spring. Thrust 514 from the rear tilt fan 504 may exceed the preload of the spring element 512 at a predetermined rpm speed (thrust threshold) of the rear tilt fan 504, causing the arm 508 and the rear tilt fan 504 to tilt. Thus, the rear tilt fan 504 may move passively and is "passive" in the sense that no actuator or power mechanism is coupled to the rear tilt fan 504 to tilt it from a vertical position to a horizontal position or vice versa. Nevertheless, by utilizing a passive tilt mechanism actuated by the thrust of the aft inclined fan 504, the aft inclined fan 504 is configured to pivot or tilt from a vertical lift position (in which the aft inclined fan 504 may be used for thrust) to a forward flight position (in which the aft inclined fan 504 may not be used for thrust). Furthermore, the aft inclined fan 504's passive movement capability allows the aft inclined fan 504 to be mechanically independent from the other aft inclined fans or the forward inclined fans. Thus, for example, as described, the aft inclined fan 504's ability to tilt from a vertical position to a horizontal position (and vice versa) may not be dependent on the function of the other inclined fans. For example, failure of the tilt mechanism or actuator of the other inclined fans (forward or aft) may not affect the continued function of the aft inclined fan 504.

[0053] For example, in the exemplary VTOL aircraft 100 shown in FIG. 2A, all of the front fans (fans numbered 1-6) may be active tilt fans, and all of the rear fans (fans 7-12) may be passive tilt fans. This configuration can result in reduced vibration for the VTOL aircraft because the rear fans receive highly turbulent wakes from the wings, while the front fans draw in clean air, resulting in quieter flight and lower vibrations. The front fans may be coupled in various ways, such that any number of front fans may be coupled to an actuator (e.g., each front fan may be coupled to its own individual actuator, or any number of front fans may be grouped together and coupled to an actuator).

[0054] 5B shows the positions of forward inclined fan 502 and aft inclined fan 504 during an inbound (e.g., flight to landing) and outbound (e.g., stationary to flight) transition of the VTOL aircraft. At stage 550, VTOL aircraft 500 is in a stationary mode (e.g., on the ground). Aft inclined fan 504 is in a vertical position relative to support element 506 (or the fuselage of VTOL aircraft 500), and forward inclined fan 502 is in a horizontal position relative to support element 506 to which forward inclined fan 502 and aft inclined fan 504 are coupled.

[0055] In stage 552, VTOL air vehicle 500 is in vertical flight mode (e.g., takeoff / landing mode). Rear inclined fan 504 remains in a vertical position relative to support element 506, and front inclined fan 502 is inclined at an angle toward the fuselage of VTOL air vehicle 500. The total vertical thrust from front inclined fan 502 and rear inclined fan 504 begins to lift VTOL air vehicle 500 if VTOL air vehicle 500 is in the current, or descends the aircraft toward the ground if VTOL air vehicle 500 is airborne. In stage 552, the thrust does not exceed the spring preload of arms 508.

[0056] At stage 554, VTOL air vehicle 500 is in a hover mode in the air. Thrust exceeds the spring preload of arms 508, and rear inclined fan 504 is tilted to a horizontal position (e.g., parallel to support element 506 and / or fuselage). Front inclined fan 502 is also in a horizontal position relative to support element 506. At stage 554, both front inclined fan 502 and rear inclined fan 504 provide thrust, which may enable VTOL air vehicle 500 to hover.

[0057] At stage 556, VTOL air vehicle 500 is in a transition mode. Rear inclined fan 504 remains in a horizontal position relative to support element 506, and front inclined fan 502 is angled away from support element 506. Front inclined fan 502 is transitioning to a forward flight mode in which front inclined fan 502 is in a vertical position relative to support element 506.

[0058] In stage 558, VTOL air vehicle 500 is fully in the wind and in forward flight mode. Aft inclined fan 504 is tilted to a vertical position relative to support elements 506 (e.g., perpendicular to support elements 506 and / or the fuselage). Forward inclined fan 502 is likewise in a vertical position relative to support elements 506 and provides thrust to move VTOL air vehicle 500 forward. In this exemplary embodiment, aft inclined fan 504 may be unused, providing minimal or no thrust, during forward flight. According to various embodiments, the blades of aft inclined fan 504 may be folded when aft inclined fan 504 is not being used (e.g., in forward flight mode).

[0059] The sequential transition from stage 550 to stage 558 indicates an outbound transition in which VTOL air vehicle 500 takes off from a stationary position on the ground to forward flight in the air. The sequential transition from stage 558 to stage 550 indicates an inbound transition in which VTOL air vehicle 500 lands on the ground from forward flight in the air.

[0060] 6A-6C illustrate a VTOL aircraft 600 in which the rear inclined fan 604 tilts from a horizontal position relative to a support element or wing (e.g., a vertical flight position) to a vertical position relative to the support element or wing (e.g., a forward flight position). During forward flight, the rear inclined fan 604 can move passively, for example, tilting due to a lack of centrifugal force on the blades 606 of the rear inclined fan 604. According to various embodiments, the tilt of the rear inclined fan 604 can be passive (e.g., achieved without the use of an actuator), such as using a mechanism (e.g., a spring-loaded mechanism) as described with respect to FIG. 5A. The rear inclined fan 604 can be used for vertical flight (e.g., takeoff, hovering, and / or landing) and may not have variable pitch. The forward inclined fan 602 can include various aspects of a control system, such as those described with reference to FIGS. 3A-3C and / or 4A-4C. The forward inclined fan 602 can have variable pitch, as previously described.

[0061] In addition to tilting the aft inclined fan 604, the blades 606 of the aft inclined fan 604 can fold circumferentially toward one another due to aerodynamic drag experienced during forward flight, as shown in FIGS. 6D-6F . While FIGS. 6A-6F depict a single blade 606 for ease of understanding, it is understood that the aft fan 604 may include any number of blades. Such folding of the aft inclined fan 604 can reduce aerodynamic drag on the VTOL aircraft 100 during forward flight. As the blades 606 fold toward one another, the first crank slider 608 coupled to the second crank slider 610 can tilt the aft inclined fan 604 into a low-drag configuration. The blades 606 fold from perpendicular to the axis of rotation of the aft inclined fan 604 to parallel to the axis of rotation in the folded position. According to various embodiments, the folding of the blades 606 may be coupled to the tilt of the aft inclined fan 604. For example, the spring elements can keep the rear inclined fan 604 in a forward flight configuration in which the axis of rotation of the rear inclined fan 604 is parallel to the motion of the VTOL aircraft. The spring elements can tilt the rear inclined fan 604 substantially simultaneously with folding the blades 606 of the rear inclined fan 602. When the deployment of the blades 606 is coupled with the tilt of the rear inclined fan 604, the spin of the propulsion motor of the rear inclined fan 602 tilts the rear inclined fan 602 into a desired configuration to provide a desired thrust direction.

[0062] According to various embodiments, the forward tilt fan 602 may include a variable pitch mechanism as described above. As the forward tilt fan 602 tilts from a hover configuration to a forward flight configuration, the pitch angle of the blades can change. The variable pitch mechanism includes an actuator that can twist the blades about the blade axis 612. The tilt of the forward tilt fan 602 may be coupled to the pitch of the blades of the forward tilt fan 602.

[0063] 7A-7C illustrate an exemplary control system 700 including a tilt fan 702, where the tilt mechanism 704 includes four bars 706. As previously described, the tilt mechanism 704 may be located entirely within a support element 708. For example, incorporating the tilt mechanism 704 within the support element 708 can provide a tight or flush connection between the tilt fan 702 and the support element on the leading edge; such a design can reduce drag in forward flight positions. FIGS. 7A-7C illustrate a series of views in which the tilt mechanism 704 tilts the tilt fan 702 from a horizontal position (shown in FIG. 7A ) to a transition position (shown in FIG. 7B ) to provide thrust for forward flight and to a vertical position (shown in FIG. 7C ) to provide thrust for vertical lift. The control system 700 may include one or more actuators (not shown) coupled to the tilt mechanism 704, such as by a drive shaft, as previously described.

[0064] The tilt fan 702 may be a forward tilt fan 702. The control system 300 described above in connection with FIGS. 3A-6F illustrates the forward tilt fan 302 connected to the actuator 312 via a single bar 316 attached to the forward tilt fan 302 and drive shaft 314. Conversely, the tilt mechanism 704 may include four bars 706 (e.g., a four-bar linkage) that provide multiple connections to the forward tilt fan 702. According to various embodiments, the four-bar tilt mechanism 704 can provide the advantage of faster and easier alignment of the forward tilt fan 702 with the support element 708 in a forward flight position, such as for reducing drag without requiring multiple movements or an articulated fairing. Additionally, the four-bar 706 embodiment of the control system 700 can allow a load path between the forward tilt fan 702 and the support element 708 to extend through the wing 710. The load path exhibits significant vibration loads that tend to fracture components and change the size of joints. Instead of a single pivot point, the four-bar tilt mechanism 704 distributes the load across four bars 706. Thus, the four bars act like additional load paths.

[0065] 8A-8C illustrate an exemplary control system 800 including a front tilt fan 802 and a rear tilt fan 804. According to various embodiments, the control system 800 may include a tilt mechanism 806 that operably connects the front tilt fan 802 and the rear tilt fan 804 to an actuator, as described above.

[0066] In various embodiments, one or both of the front inclined fan 802 and the rear inclined fan 804 can be coupled (connected) to a tilt mechanism 806 via a front 4-bar tilt mechanism 808 and a rear 4-bar tilt mechanism 810, respectively, as shown in FIGS. 8A-8C . The front 4-bar tilt mechanism 808 and the rear 4-bar tilt mechanism 810 may be provided within a support element 814 and connected to an actuator (not shown) via a single shaft 812 adapted to tilt both the front inclined fan 802 and the rear inclined fan 804 simultaneously (e.g., substantially simultaneously). The actuator may be provided in the center of the support element 814 or within the wing 816, as described above. 8A-8C show a series of views in which the four-bar tilt mechanism 808, 810 tilts the front and rear tilt fans 802, 804 from a horizontal position (shown in FIG. 8A) to a transition position (shown in FIG. 8B) to provide thrust for forward flight, and to a vertical position (shown in FIG. 8C) to provide thrust for vertical lift.

[0067] In various embodiments, as shown in FIGS. 8-1A-8-1C, the four-bar tilt mechanisms 808, 810 may be further coupled via a single shaft 812 to a drive shaft 818 mounted on the wing 816. Thus, the four-bar tilt mechanisms 808, 810 may be driven by the drive shaft 818 via the wing 816. FIGS. 8-1A-8-1C show a series of views in which the four-bar tilt mechanisms 808, 810 tilt the front and rear tilt fans 802, 804 from a horizontal position (shown in FIG. 8-1A) to a transitional position to provide thrust for forward flight and to a vertical position (shown in FIG. 8-1C) to provide thrust for vertical lift.

[0068] According to various embodiments, rather than drive shaft 818 being a single linear structure (such as drive shaft 314), drive shaft 818 may include multiple linear structures. For example, drive shaft 818 may comprise multiple shafts 820, which may be connected via respective connecting joints 822. In operation, shaft 820A may be directly coupled to an actuator and may rotate similarly to drive shaft 314. Shaft 820A may be coupled (at joint 822) to shaft 820B, which adjusts angularly as shaft 820A moves. Additionally, shaft 820C may be coupled (at joint 824) to shaft 820B and may be coupled at an opposite end to single shaft 812 to provide motion to tilt mechanism 806. The use of multiple shafts 820 may enable similar motion as a single shaft (such as drive shaft 314), but may utilize less space and / or better meet space limitations of wing 816 and / or support element 814.

[0069] In fault-tolerant aircraft designs, it may be beneficial for the tilt mechanism to be designed to be “fail-safe,” meaning that in the event of a tilt mechanism failure, the tilt mechanism can remain in or move to a safe configuration, providing balance to the VTOL aircraft and preventing loss of control of the VTOL aircraft. Generally, for VTOL aircraft, the thrust required from each fan during hovering is higher than the thrust required from each fan during forward flight. Therefore, in the event of a failure, a fail-safe would be achieved if the tilt mechanism could always move to a hovering configuration so that the tilt fans are in a vertical lift position, even in the event of an actuator failure. Therefore, according to various embodiments, a fail-safe mechanism, such as a spring element or similar mechanism (e.g., a hydraulic piston), may be provided as part of the tilt mechanism, which can act to tilt or maintain the tilt fan in a hovering position. To tilt the fan into a forward flight configuration, the actuator must overcome the force of the spring element. Specifically, in the event of an actuator failure, the spring element of the tilt mechanism can move the tilt mechanism so that the tilt fan is in a vertical lift position to provide downward thrust.

[0070] 9 shows an example schematic diagram of a VTOL aircraft control system 900 having one drive 910 (e.g., actuator, compressor, valve, or primary piston) driving at least two tilt mechanisms 912, 914 coupled to respective tilt fans 902, 904. The tilt fans 902, 904 may be in various locations on the VTOL aircraft and are not necessarily tilt fans located on the same wing or the same support element.

[0071] When designing control system 900, a "coupling scheme" in which tilt fans are interconnected by particular tilt mechanisms can be determined. Thus, the coupling scheme can determine the functions that the tilt fans correspond to one another. For example, the coupling scheme can include a first subset of tilt mechanisms, such as tilt mechanism 912 and tilt mechanism 914, that can be operably coupled to drive device 910 (e.g., actuator). Control system 900 can further include a second subset of tilt mechanisms, a third subset of tilt mechanisms, etc., that can each be operably coupled to one or more drive devices.

[0072] The plurality of tilt fans may be divided into groups, such as a second group of tilt fans, a third group of tilt fans, etc., each having a separate subset of tilt mechanisms. Each group or groups of tilt fans (e.g., the first and second groups of tilt mechanisms) may be operably coupled to the same actuator. For example, an actuator may tilt the first group of tilt fans and the second group of tilt fans. Conversely, a group of tilt fans may be operably coupled to a separate actuator via a subset of tilt mechanisms. For example, a second actuator may be coupled to the second subset of tilt mechanisms such that the second actuator simultaneously tilts the second group of tilt fans coupled to the second subset of tilt mechanisms.

[0073] According to various coupling schemes contemplated herein, the coupling scheme may be diametrically symmetric about the center of gravity of the VTOL aircraft 100. The coupling scheme may further determine the number of tilt mechanisms and actuators required. In determining the coupling scheme, designers may take into account cost, weight, safety, and various other decisions related to aircraft design.

[0074] For example, tilt fans 902, 904 may be selected to pair based on a failure condition. According to various embodiments, if one of the 12 fans fails, it is preferable to shut down the symmetric tilt fan to maintain aircraft balance. The corresponding tilt fan is diametrically symmetrical to the failed fan with respect to the aircraft's center of gravity. For example, as shown in FIG. 9 , tilt fan number 8 (904) is diametrically symmetrical to tilt fan number 5 (902) and thus may be operatively coupled to tilt fan number 5 (902). Thus, tilt mechanism 914 for tilting tilt fan number 8 (904) and tilt mechanism 912 for tilting tilt fan number 5 (902) may be coupled to a single drive unit 910. Thus, if either fan 902 or 904 fails, the corresponding fan 904 or 902 may be shut down. 9, a single drive (e.g., ball screw actuator) 910 may be connected to tilt fan number 8 (904) and tilt fan number 5 (902) via hydraulic lines 920 and 922, respectively, that extend through the wing and fuselage. The two tilt mechanisms 912, 914 are coupled to each other to move (e.g., tilt) together. According to various embodiments, other mechanisms for operably coupling the tilt fans may be used, as described throughout.

[0075] Similar to the coupling of tilt fans 902, 904 to drives 910, various groups of tilt fans can be paired or grouped together. For example, other sets of two tilt fans may be selected based on diametric symmetry. In other embodiments, other groups of tilt fans may be coupled to actuators according to other coupling schemes. Furthermore, while tilt fans 902, 904 are paired based on diametric symmetry, other tilt fans within the same VTOL aircraft 100 may be paired based on other criteria and thus may be on the same support element or the same wing. Other groups or pairs of tilt fans may utilize the same drives 910 as tilt fans 902, 904 or may otherwise share control system components. However, in various embodiments, other groups or pairs of tilt fans may be equipped with separate tilt mechanisms and actuators.

[0076] According to various embodiments, control system 900 may be part of a flight control system for VTOL aircraft 100. In some embodiments, control system 900 may include a memory that stores executable instructions that, when executed by one or more processors of the control system, cause the one or more processors to tilt one or more of tilt fans 902, 904 using tilt mechanisms 912, 914 according to a coupling scheme.

[0077] As mentioned above, any number of actuators can be used to drive the tilt mechanisms of the tilt fans. Figures 10 and 11 show exemplary embodiments with different numbers of actuators. As shown in Figures 10 and 11, the control system coupling scheme includes all of the multiple tilt mechanisms (e.g., primary and secondary cylinders) such that a shared actuator tilts all of the multiple tilt fans.

[0078] FIG. 10 illustrates an exemplary control system 1000 including an actuator 1002 operably connected to multiple (e.g., 12) primary cylinders 1004. For example, the multiple primary cylinders 1004 can function to distribute power from the actuator 1002 to respective secondary cylinders 1006 coupled to the tilt fans. Thus, a tilt mechanism can include a first primary cylinder 1004 operably coupled to a first secondary cylinder 1006, which can be operably coupled to a first tilt fan. As described below in connection with FIGS. 12A-12B , the actuator 1002 can include a shaft (e.g., a ball screw shaft). As the shaft rotates, the actuator 1002 can apply force to multiple plungers, each respectively included within each of the multiple primary cylinders 1004. Thus, rotation of the shaft of the actuator 1002 can create hydraulic pressure within the primary cylinders 1004. The hydraulic pressure within the primary cylinders 1004 can be applied to each secondary cylinder 1006 via respective hydraulic lines. The secondary cylinders 1006 can act to convert hydraulic force in the hydraulic lines into mechanical force, such as with a plunger. Each of the secondary cylinders 1006 can then be coupled to a tilt fan of the VTOL aircraft, and the plunger of the secondary cylinder 1006 can cause the tilt of the respective tilt fan. Thus, a single actuator 1002 can operatively tilt each of the tilt fans simultaneously by creating hydraulic pressure that is applied to the tilt fans through the respective secondary cylinders 1006. According to various embodiments, a similar functional effect may be achieved using a non-hydraulic system, such as a mechanical system (e.g., using gears and a mechanical tilt mechanism) coupling the actuator 1002 to the respective tilt fan.

[0079] 10 can result in a reduction in the number of components required to tilt multiple tilt fans by having the multiple tilt fans actuated by a single actuator. Furthermore, by only requiring control of a single actuator, programming for controlling the multiple tilt fans can be simplified. However, shared components can increase the likelihood that a single failure (e.g., actuator failure) will result in an inoperable aircraft. Therefore, as described below, additional control system components may be further included in the VTOL aircraft 100 to provide redundant powering and tilting of the tilt fans.

[0080] FIG. 11 shows an exemplary control system 1100 including two actuators 1102 and 1104 operating in parallel to power respective primary cylinders 1106 and 1108, respectively. For example, in a VTOL aircraft 100 having 12 tilt fans, each of the actuators 1102 and 1104 may have 12 corresponding primary cylinders 1106 and 1108. A pair of primary cylinders 1106 and 1108 may be coupled to a particular secondary cylinder 1110 corresponding to a tilt fan via hydraulic lines 1112 and 1114. For example, actuator 1102 may be coupled to and power primary cylinder 1106, and actuator 1104 may be coupled to and power primary cylinder 1108. Both primary cylinders 1106 and 1108 may be coupled to secondary cylinder 1110 to control a tilt fan (e.g., tilt fan number 6). Similarly, the "pair" of primary cylinders coupled to actuator 1102 and another primary cylinder coupled to actuator 1104 can both be connected to another single secondary cylinder. Although FIG. 11 shows hydraulic lines 1120, 1122 for a single secondary cylinder 1110, the secondary cylinders of all tilt fans may have similar hydraulic line connections to their respective pairs of primary cylinders.

[0081] This configuration of the control system 1100 therefore adds redundancy to increase the fault tolerance of the overall system. A failure (e.g., a leak) anywhere within the control system 1100 could result in fan failure. However, because each actuator 1102, 1104 (and its respective primary cylinder 1106, 1108) is independent of the other, in the event of a failure, only a single tilt fan fails. Each actuator 1102, 1104 may include a ball screw actuator. The redundant ball screws eliminate them as single points of failure (e.g., the ball screws are not back-drivable).

[0082] According to various embodiments, the system may include additional actuators (e.g., a third actuator in addition to the first two actuators that also drives 12 primary cylinders). According to some embodiments, the system may include multiple actuators, each actuator driving any number of primary cylinders (e.g., 1-12). Thus, the control system 1100 may have multiple sets of respective actuators and primary cylinders in parallel with the illustrated actuators 1102, 1104 and primary cylinders 1106, 1108, for example, to provide an additional layer of fault protection.

[0083] According to various embodiments, the example control system 1100 of Figure 11 may further include a pitch mechanism in addition to the tilt mechanism coupled to each of the tilt fans. The pitch and tilt mechanisms may each correspond to one of the secondary cylinders 1110. The primary cylinders 1106, 1108 (and thus the actuators 1102, 1104) can drive both the tilt and pitch mechanisms together.

[0084] 12A shows a cross-sectional view of an exemplary primary cylinder system 1200, according to various embodiments. Generally, the primary cylinder may be powered by one or more actuators, such as a ball drive actuator. It should be understood that various other mechanisms that achieve the same function may also or additionally be used.

[0085] In FIG. 12A , primary cylinder system 1200 can include a ball screw shaft 1202, which can be disposed, for example, at the center of a circular structure. The ball screw shaft 1202 can be configured to provide pushing and pulling forces to plungers in primary cylinders 1204, which are disposed circumferentially around the ball screw shaft 1202. Primary cylinder system 1200 can further include multiple ports 1206, at least one port 1206 corresponding to each primary cylinder 1204. The ports 1206 can be disposed proximate the outer edge of the circular structure, such as radially away from the ball screw shaft 1202. Functionally, the ports 1206 can act as hydraulic connections for forces applied to the primary cylinders 1204 by the ball screw shaft 1202. For example, when a pushing force is applied by the ball screw shaft, the plungers of the primary cylinders 1204 can push hydraulic fluid out of the primary cylinders 1204. Conversely, when a pulling force is applied to the primary cylinders 1204 by the ball screw shaft 1202, suction can draw hydraulic fluid through the ports 1206 into each primary cylinder 1204. Accordingly, each of the ports 1206 can be coupled to a hydraulic line that transports hydraulic fluid to the various tilt mechanisms to effect tilt of the tilt fan, as previously described. For example, each of the primary cylinders 1204 can be connected to a hydraulic line via the ports 1206. This hydraulic line can then be connected to, for example, a secondary cylinder for a particular tilt fan.

[0086] 12B shows a cross-sectional view of a primary cylinder system 1201 incorporating two redundant pistons within a single primary cylinder 1204, according to various embodiments of the present disclosure. The primary cylinder system 1201 may include a first ball screw actuator 1210 and a second ball screw actuator 1220. The first and second ball screw actuators 1210, 1220 may, for example, be positioned opposite each other and concentric with a circular structure that houses the primary cylinder 1204. The first ball screw actuator 1210 may be coupled to the primary cylinder system 1201 via a left-side mechanism 1212, and the second ball screw actuator 1220 may be coupled to the primary cylinder system 1201 via a right-side mechanism 1222.

[0087] Both ball screw actuators 1210 and 1220 may be connected to the same hydraulic circuit and therefore both may act to move the same plunger of primary cylinder 1204. According to various embodiments, each of ball screw actuators 1210, 1220 may provide an opposing force to the other. For example, the first ball screw actuator 1210 may push the plunger from the left side toward port 1206, which is located in the center of primary cylinder 1204. The second ball screw actuator 1220 may push the plunger from the right side toward port 1206. Thus, each may provide an equal amount of hydraulic force through port 1206. However, to provide a fail-safe configuration, each of the ball screw actuators 1210, 1220 may be configured to be movable beyond the center of the primary cylinder 1204 such that if one of the ball screw actuators 1210, 1220 is unable to perform the full range of motion necessary to generate the desired hydraulic pressure (such as in the event of a failure), the other ball screw actuator 1210, 1220 may be configured to move beyond the center of the primary cylinder 1204 to provide the desired hydraulic force. Specifically, if one of the ball screw actuators 1210, 1220 fails, the remaining ball screw actuator 1210, 1220 can move to the location where the failed ball screw actuator 1210, 1220 stopped, thereby producing the same maximum displacement as both ball screw actuators 1210, 1220 would perform in tandem.

[0088] The primary cylinder system 1201 shown in Figure 12B is an exemplary implementation of the primary cylinder system 1200 shown in Figure 12A. In the primary cylinder system 1201 of Figure 12B, the primary cylinder 1204 can be much smaller (i.e., about half the size) compared to other systems that are provided with an entirely separate, additional primary cylinder 1204. Additionally, the embodiment shown in Figure 12B can reduce the number of seals used in the primary cylinder system 1201, and therefore, can have fewer components that can leak or fail.

[0089] According to various embodiments, a flight control system (or another control system coupled to VTOL aircraft 100) can control the tilt mechanism to switch the tilt fan configuration from a forward flight position to a vertical position, and from a vertical position to a forward flight position. According to various embodiments, the control system (e.g., a flight control system) can control the tilt fan between the two positions based on sensor data and / or flight data received from sensors (e.g., sensors measuring air temperature, electric motor temperature, aircraft airspeed, etc.), computers, and other input / output devices coupled to the aircraft.

[0090] For simplicity, various active and passive circuit components are not shown in the figures. In the foregoing specification, embodiments of the present disclosure have been described with reference to numerous specific details that may vary from implementation to implementation. Accordingly, the specification and drawings should be regarded in an illustrative rather than a limiting sense. The sole and exclusive indication of the scope of the present disclosure, and what is intended by the applicant to be the scope of the present disclosure, is the literal equivalents of the claims issuing from this application, the specific forms in which such claims issue, including subsequent amendments. The specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure.

[0091] The electronic components of the described embodiments may be specially constructed for the required purposes, or may comprise one or more general-purpose computers selectively activated or reconfigured by a computer program stored in the computers. Such computer programs may be stored on any type of computer-readable storage medium, such as, but not limited to, a floppy disk, an optical disk, a DVD, a CD-ROM, a magneto-optical disk, a read-only memory (ROM), a random-access memory (RAM), an EPROM, an EEPROM, a magnetic or optical card, an application-specific integrated circuit (ASIC), or any type of medium suitable for storing electronic instructions, each coupled to a computer system bus.

[0092] Additionally, spatially relative terms such as "front" or "rear" may be used to describe the relationship of one element and / or feature to another, e.g., as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device during use and / or operation in addition to the orientation shown in the figures. For example, if the device in the figures is turned upside down, an element described as a "front" surface may be oriented "rear" from the other element or feature. The device may be oriented in other ways (e.g., rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein will be interpreted accordingly.

[0093] While the invention has been described with reference to specific embodiments, those skilled in the art and having access to this disclosure will recognize that variations and modifications will be possible.

[0094] It should be understood that all numerical values ​​used herein are for illustrative purposes and are subject to change. In some cases, ranges are specified to provide a sense of scale, but values ​​outside the disclosed ranges are not excluded.

[0095] It should also be understood that all figures herein are intended as schematic representations. Unless otherwise specified, the figures do not imply any particular physical arrangement of elements shown therein, or that all elements shown are required. Those skilled in the art with access to this disclosure will understand that elements shown in the figures or otherwise described in this disclosure can be modified or omitted, and other elements not shown or described can be added.

[0096] The above description is illustrative and not limiting. Many variations of the embodiments will become apparent to those skilled in the art upon review of this disclosure. Accordingly, the scope of patent protection should not be determined with reference to the above description, but instead with reference to the following claims along with their full scope or equivalents.

Claims

1. The torso and at least one wing coupled to the fuselage; a plurality of support elements coupled underneath the at least one wing; a plurality of tilt fans, each coupled to a support element of the plurality of support elements via a tilt mechanism and configured to move between a vertical lift position and a forward flight position, a first group of tilt fans configured to move to the vertical lift position upon a malfunction affecting the function of one or more tilt fans of the first group; An aircraft comprising:

2. 2. The aircraft of claim 1, wherein a forward inclined fan of the plurality of inclined fans and an aft inclined fan of the plurality of inclined fans are coupled to opposite ends of a first support element of the plurality of support elements, the forward inclined fan being provided at a leading edge of the at least one wing, and the aft inclined fan being provided at a trailing edge of the at least one wing.

3. 3. The aircraft of claim 2, wherein the forward tilt fan and the aft tilt fan are coupled to the first support element via a first tilt mechanism provided within the first support element.

4. 3. The aircraft of claim 2, wherein at least one of the forward inclined fan or the aft inclined fan is coupled to the first support element via a first tilt mechanism provided within the first support element, the first tilt mechanism including a four-bar linkage.

5. 10. The aircraft of claim 1, further comprising at least one second actuator configured to simultaneously actuate a second group of inclined fans to move between the vertical lift position and the forward flight position.

6. 2. The aircraft of claim 1, wherein the first group of inclined fans comprises a plurality of forward inclined fans disposed on the leading edge of the at least one wing.

7. 7. The aircraft of claim 6, wherein the plurality of inclined fans further comprises a plurality of aft inclined fans disposed on a trailing edge of the at least one wing, the plurality of aft inclined fans configured to passively move from the vertical lift position to the forward flight position, the plurality of aft inclined fans being mechanically independent of one another.

8. a passive tilt mechanism coupled to a rear portion of a first support element of the plurality of support elements; The passive tilt mechanism includes: an arm rotatably coupling the rear-inclined fan to the first support element; a spring element spanning the rear-inclined fan and the first support element, the spring element configured to rotate the arm when a horizontal thrust exceeds a thrust threshold; at least one travel limiting stop configured to limit the angle of rotation of the arm; Equipped with 10. The aircraft of claim 1, wherein the blades of the aft tilt fan fold relative to one another during forward flight.

9. The torso and at least one wing coupled to the fuselage; a plurality of support elements coupled underneath the at least one wing; a plurality of tilt fans, each coupled to a support element of the plurality of support elements via a tilt mechanism; a first actuator configured to simultaneously actuate a first group of the plurality of tilt fans to move between the vertical lift position and the forward flight position, the first actuator configured to move the first group of the tilt fans to the vertical lift position upon a failure; and An aircraft comprising:

10. 10. The aircraft of claim 9, wherein at least a portion of the first actuator is provided within at least one support element of the plurality of support elements.

11. 10. The aircraft of claim 9, further comprising a plurality of primary cylinders operably coupled to the first actuator, each of the plurality of primary cylinders operably coupled to a secondary cylinder of a plurality of secondary cylinders, each of the plurality of secondary cylinders operably coupled to a given tilt fan of the first group of tilt fans, and the plurality of secondary cylinders configured to receive hydraulic pressure from the plurality of primary cylinders.

12. 10. The aircraft of claim 9, further comprising one or more tilt mechanisms coupling the first group of tilt fans to one or more support elements of the plurality of support elements, the first actuator coupled to the one or more tilt mechanisms.

13. 13. The aircraft of claim 12, wherein the one or more tilt mechanisms further comprise a drive shaft disposed within the at least one wing, the drive shaft operatively coupling the first actuator to the first group of tilt fans.

14. 13. The aircraft of claim 12, wherein the first actuator comprises a compressor, and the one or more tilt mechanisms further comprise hydraulic lines connecting the one or more tilt mechanisms to the first actuator.

15. 13. The aircraft of claim 12, wherein at least a portion of the first actuator is provided within the at least one wing and at least a portion of the one or more tilt mechanisms is provided within one or more support elements of the plurality of support elements.

16. The torso and at least one wing coupled to the fuselage; a plurality of forward tilt fans each coupled to a leading edge of the at least one blade via a tilt mechanism; a first actuator configured to simultaneously actuate a first group of the plurality of forward tilt fans to move them between a vertical lift position and a forward flight position; a plurality of variable pitch mechanisms each coupled to one of the plurality of forward inclined fans and configured to adjust the pitch of the blades of the corresponding forward inclined fan based on the direction or speed of the aircraft; An aircraft comprising:

17. 17. The aircraft of claim 16, wherein the inclination of a first forward inclined fan of the plurality of forward inclined fans is coupled to the pitch of the blades of the first forward inclined fan.

18. 17. The aircraft of claim 16, wherein the first actuator drives the tilt mechanism and one or more of the plurality of variable pitch mechanisms associated with the first group of the plurality of forward tilt fans.

19. 17. The aircraft of claim 16, further comprising a plurality of rear-inclined fans each coupled to a trailing edge of the at least one wing.

20. 20. The aircraft of claim 19, wherein one forward inclined fan of the first group of the plurality of forward inclined fans and one aft inclined fan of the plurality of aft inclined fans are coupled to a first support element via a first tilt mechanism, the first support element being coupled below the at least one wing and housing at least one of the first actuator and the first tilt mechanism.

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