Hybrid propulsion vertical take-off and landing aircraft

A hybrid propulsion aircraft is described having a distributed electric propulsion system. The distributed electric propulsion system includes a turbo shaft engine that drives one or more generators through a gearbox. The generator provides AC power to a plurality of ducted fans (each being driven by an electric motor). The ducted fans may be integrated with the hybrid propulsion aircraft's wings. The wings can be pivotally attached to the fuselage, thereby allowing for vertical take-off and landing. The design of the hybrid propulsion aircraft mitigates undesirable transient behavior traditionally encountered during a transition from vertical flight to horizontal flight. Moreover, the hybrid propulsion aircraft offers a fast, constant-altitude transition, without requiring a climb or dive to transition. It also offers increased efficiency in both hover and forward flight versus other VTOL aircraft and a higher forward max speed than traditional rotorcraft.

TECHNICAL FIELD

The present invention relates to the field of vertical takeoff and landing aircraft; more particularly, to a hybrid propulsion aircraft; even more particularly, to a hybrid propulsion aircraft having a tilt-wing configuration. The vertical takeoff and landing aircraft may be manned or unmanned.

BACKGROUND

There has long been a need for vertical take-off and landing (“VTOL”) vehicles that are capable of being deployed from confined spaces. In fact, many situations favor vehicles, specifically unmanned aerial vehicles (“UAVs”), which can launch and recover vertically without requiring complex or heavy ground support equipment. The ability to organically deploy a UAV is particularly attractive in situations where a runway is unavailable or inaccessible. Until recently, however, the efficiency penalty associated with incorporating a hover phase of flight, the complexity associated with transition from vertical (e.g., hover) to horizontal flight (e.g., forward flight, or cruise), and the necessity to reduce or eliminate exposure of ground personnel to exposed high-speed rotors have hindered attempts to develop efficient VTOL UAVs.

In recent years, however, advancements have been made to improve overall efficiency of VTOL aircraft and VTOL UAVs. For example, commonly owned U.S. Pat. No. 7,857,254, to Robert Parks, discloses a short/vertical take-off and landing aircraft that stores required take-off power in the form of primarily an electric fan engine, and secondarily in the form of an internal combustion engine. Similarly, commonly owned U.S. Patent Publication No. 2015/0021430, to James Donald Paduano et al., discloses a long-endurance, high-aspect ratio VTOL UAV that may be launched from confined spaces.

Despite the forgoing, however, a need exists for a further improved VTOL aircraft, such as a hybrid propulsion aircraft, which may employ a tilt-wing configuration. The hybrid propulsion aircraft, as disclosed herein, may be used for land-based operations, ship-board operations, operations requiring short or long range deployment, as well as commercial applications.

SUMMARY OF THE INVENTION

The present invention is directed to a hybrid propulsion aircraft; even more particularly, to a hybrid propulsion aircraft having a tilt-wing configuration. The vertical takeoff and landing aircraft may be manned or unmanned.

According to a first aspect, a hybrid propulsion vertical take-off and landing (VTOL) aerial vehicle comprises: a fuselage; an engine, such as a turbo shaft engine, operatively coupled with a plurality of generators, the engine and the plurality of generators being positioned within the fuselage; a primary wing set, the primary wing set comprising a first plurality of integrated ducted fans, each of said first plurality of integrated ducted fans being operatively coupled with at least one of said plurality of generators; and a canard wing set, the canard wing set comprising a second plurality of integrated ducted fans, each of said second plurality of integrated ducted fans being operatively coupled with at least one of said plurality of generators, wherein the primary wing set or the canard wing set is pivotally attached to the fuselage.

According to a second aspect, a hybrid propulsion vertical take-off and landing (VTOL) aerial vehicle comprises: a fuselage; an engine operatively coupled with one or more generators to generate electric power, the engine and the one or more generators being positioned within the fuselage; a primary wing set having a first plurality of integrated ducted fans to collectively generate a first aggregate thrust, each of said first plurality of integrated ducted fans driven by an electric fan motor operatively coupled with at least one of said one or more generators; and a canard wing set having a second plurality of integrated ducted fans to collectively generate a second aggregate thrust, each of said second plurality of integrated ducted fans driven by an electric fan motor operatively coupled with at least one of said one or more generators, wherein the hybrid propulsion VTOL aerial vehicle is operable in a hover mode and a horizontal flight mode, wherein each of the canard wing set and the primary wing set are configured to transition between a vertical wing configuration in the hover mode and a horizontal wing configuration in the horizontal flight mode.

In certain aspects, the canard wing set and the primary wing set are pivotally attached to the fuselage.

In certain aspects, said canard wing set and said primary wing set provide both lift and propulsion.

In certain aspects, at least one of the primary wing set and the canard wing set are anhedral.

In certain aspects, one or more of said first or second plurality of integrated ducted fans comprises an adjustable thrust nozzle, which may be independently controllable.

In certain aspects, each of said first plurality of integrated ducted fans and said second plurality of integrated ducted fans comprises an adjustable thrust nozzle, which may be independently controllable.

In certain aspects, each of said first plurality of integrated ducted fans and said second plurality of integrated ducted fans are distributed evenly along the primary wing set's wingspan.

In certain aspects, the first plurality of integrated ducted fans are evenly distributed along the primary wing set's wingspan.

In certain aspects, the second plurality of integrated ducted fans are evenly distributed along the canard wing set's wingspan.

In certain aspects, the one or more generators includes a first generator operably coupled with: (1) two of said first plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage; and (2) two of said second plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage.

In certain aspects, the one or more generators includes the first generator and a second generator, the second generator operably coupled with: (1) two of said first plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage; and (2) two of said second plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage.

In certain aspects, the one or more generators includes the first generator, the second generator, and a third generator, the third generator operably coupled with: (1) two of said first plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage; and (2) two of said second plurality of integrated ducted fans, each being positioned on opposite sides of the fuselage.

In certain aspects, the hybrid propulsion VTOL aerial vehicle further comprises a gearbox, wherein said engine and each of said one or more generators are operably coupled with the gearbox without an intervening drive shaft.

In certain aspects, each of said first and second plurality of integrated ducted fans comprises a duct chamber having a thrust assembly positioned therein, the duct chamber having an upper leading edge with one or more airflow slots to guide airflow through the upper leading edge and into the duct chamber.

In certain aspects, the ratio of the duct chamber's length to diameter is between 1.5 and 2.5.

In certain aspects, each of said first and second plurality of integrated ducted fans comprises (1) a fan having a plurality of fan blades and (2) a pitch control mechanism, the pitch control mechanism being configured to adjust a pitch of each of said plurality of fan blades.

In certain aspects, at least one of said first or second plurality of integrated ducted fans comprises (1) a fan having a plurality of fan blades and (2) a pitch control mechanism, the pitch control mechanism being configured to adjust a pitch of each of said plurality of fan blades.

In certain aspects, each of said plurality of fan blades comprises a pitch arm, each pitch arm being coupled with a translating pitch cone, wherein the translating pitch cone is configured to travel laterally perpendicular with regard to a plane defined by the fan's rotation, thereby actuating each pitch arm.

In certain aspects, the hybrid propulsion VTOL aerial vehicle further comprises a flight control unit to detect whether a first electric fan motor of a first integrated ducted fan is out of synchronization with a second electric fan motor of a second integrated ducted fan using a torque detection technique or by comparing at least one of a phase or a waveform of a voltage signal and a current signal. For example, a synchronization monitoring system may be provided that prevents a ducted fan's motor from falling out of synchronization with the other fan motors and/or generator.

In certain aspects, the hybrid propulsion VTOL aerial vehicle further comprises a flight control unit to provide feedback pertaining to an operating parameter of at least one of said first plurality of integrated ducted fans or said second plurality of integrated ducted fans to a generator controller operatively coupled with one or more of said one or more generators.

In certain aspects, each electric fan motor operates at a constant motor speed during transition between said hover mode and said horizontal flight mode.

In certain aspects, each electric fan motor and/or each of the one or more generators operate at a constant rotation per minute (RPM) during transition between said hover mode and said horizontal flight mode.

In certain aspects, each electric fan motor operates at a constant frequency during transition between said hover mode and said horizontal flight mode.

In certain aspects, the electric power generated by said one or more generators is supplied to the first plurality of integrated ducted fans and the second plurality of integrated ducted fans without converting or inverting said electric power. For example, the voltage level and/or the power level from the one or more generators may be maintained at the same level.

In certain aspects, the electric power generated by said one or more generators is filtered to remove noise and is supplied to the first plurality of integrated ducted fans and the second plurality of integrated ducted fans via a Litz wire or a metal tube having a varying diameter.

In certain aspects, the primary wing set is modular such that one or more of the first plurality of integrated ducted fans is a ducted fan module configured to removably couple with an adjacent integrated ducted fan. For example, the ducted fan module may removably couple with an adjacent integrated ducted fan at a separator plate.

DETAILED DESCRIPTION

Preferred embodiments of the present invention will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail because they may obscure the invention in unnecessary detail. For this disclosure, the following terms and definitions shall apply.

As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first set of one or more lines of code and may comprise a second “circuit” when executing a second set of one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”.

As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by an operator-configurable setting, factory trim, etc.). As used herein, the words “about” and “approximately,” when used to modify or describe a value (or range of values), mean reasonably close to that value or range of values. Thus, the embodiments described herein are not limited to only the recited values and ranges of values, but rather should include reasonably workable deviations

As used herein, the terms “aerial vehicle” and “aircraft” refer to a machine capable of flight, including, but not limited to, traditional aircraft and VTOL aircraft. VTOL aircraft may include both fixed-wing aircraft (e.g., Harrier jets), rotorcraft (e.g., helicopters), and/or tilt-rotor/tilt-wing aircraft.

As used herein, the terms “communicate” and “communicating” refer to (1) transmitting, or otherwise conveying, data from a source to a destination, and/or (2) delivering data to a communications medium, system, channel, network, device, wire, cable, fiber, circuit, and/or link to be conveyed to a destination. The term “database” as used herein means an organized body of related data, regardless of the manner in which the data or the organized body thereof is represented. For example, the organized body of related data may be in the form of one or more of a table, a map, a grid, a packet, a datagram, a frame, a file, an e-mail, a message, a document, a report, a list, or data presented in any other form.

The term “composite material” as used herein, refers to a material comprising an additive material and a matrix material. For example, a composite material may comprise a fibrous additive material (e.g., fiberglass, glass fiber (“GF”), carbon fiber (“CF”), aramid/para-aramid synthetic fibers, FML, etc.) and a matrix material (e.g., epoxies, polyimides, aluminum, titanium, and alumina, including, without limitation, plastic resin, polyester resin, polycarbonate resin, casting resin, polymer resin, thermoplastic, acrylic resin, chemical resin, and dry resin). Further, composite materials may comprise specific fibers embedded in the matrix material, while hybrid composite materials may be achieved via the addition of some complementary materials (e.g., two or more fiber materials) to the basic fiber/epoxy matrix.

Disclosed herein is a hybrid propulsion aircraft100having increased maneuverable and agility, particularly in horizontal flight, where it has demonstrated roll and pitch rates akin to a helicopter. The hybrid propulsion aircraft100is hybrid electric in that it generates propulsion using a plurality of independently controllable alternating current (AC) motor-driven ducted fans, which receive AC power from one or more turbine-driven generators, for example, as illustrated herein, three generators. The thrust from the ducted fans may be independently controlled using variable pitch fans (e.g., via a pitch control mechanism520), while the electric motors are spun at same speed and synchronized with a generator coupled thereto. The hybrid propulsion aircraft100may further employ a tilt-wing and adjustable thrust nozzles to direct and control the thrust generated by each of the ducted fans.

The hybrid propulsion aircraft's100design is advantageous in numerous ways. First, it allows for vertical take-off and landing, while mitigating undesirable transient behaviors during transition from vertical flight (i.e., hover) to horizontal flight. That is, the hybrid propulsion aircraft100provides a fast and constant-altitude transition, which does not require that the hybrid propulsion aircraft100climb or dive in order to transition. Second, the aircraft is trimmable at any point in the airspeed range, without any unstable regimes or thrust deficits during transition. Third, the hybrid propulsion aircraft100is highly efficient in both vertical and horizontal flight, while traditional VTOL aircraft are much less in one or the other. Fourth, the hybrid propulsion aircraft100does not employ exposed rotors (e.g., fan blades512), which can threaten the safety of passengers, ground crew, or equipment. Rather, the hybrid propulsion aircraft's100fan blades512and thrust assemblies500are shrouded by, for example, the wing structure, or portion thereof. Fifth, the hybrid propulsion aircraft's100wake is cold, and is at the extremes of the aircraft. Sixth, the payload bay and cockpit are near the ground, thereby providing increased accessibility. Finally, the hybrid propulsion aircraft100provides large amounts of payload power at cruise when propulsive power draws are minimal. That is, by using hybrid electric power, although most of the electric power may be required during vertical flight, a significant amount of excess power is available during horizontal flight. For example, in certain aspects, only about 35% of the power generated during horizontal flight is needed to sustain horizontal flight, therefore leaving 65% of the power for non-flight-related power needs, such as powering payload equipment.

FIGS. 1athrough 1gillustrate an example hybrid propulsion aircraft100according to an aspect of the present invention.FIG. 1aillustrates a front view of the hybrid propulsion aircraft100, whileFIG. 1billustrates a side view of the hybrid propulsion aircraft100.FIG. 1aillustrates one side of the hybrid propulsion aircraft100in a vertical wing configuration (vertical flight mode) to generate vertical thrust, and the opposite side of the hybrid propulsion aircraft100in a horizontal wing configuration (horizontal flight mode) to generate horizontal thrust.FIG. 1cillustrates a top plan view of the hybrid propulsion aircraft100, whileFIGS. 1dand 1eillustrate, respectively, rear and front isometric views of the hybrid propulsion aircraft100. Finally,FIGS. 1fand 1gillustrate side views of the hybrid propulsion aircraft100with body panel portions omitted to better illustrate certain of the internal components of the hybrid propulsion aircraft100.

The hybrid propulsion aircraft100is generally described as being unmanned and fully autonomous (i.e., requiring no remote control pilot), but a cockpit may be added to enable manned operation. Similarly, the hybrid propulsion aircraft100may be remotely controlled over a wireless communication link by a human operator, computer operator (e.g., remote autopilot), or base station. The hybrid propulsion aircraft100can also accommodate a cabin between the primary and canard wings104,106configured to carry passengers.

The hybrid propulsion aircraft100may have a primary wingspan of about 10 to 100 feet, and a canard wingspan of 5 to 50 feet. The length of the fuselage may be about 10 to 75 feet, while the overall height of the example hybrid propulsion aircraft100may be 5 to 20 feet. When loaded with a payload and wet (i.e., including fluids, such as fuel, oil, etc.), the hybrid propulsion aircraft100may weigh around 300 to 12,000 pounds. As one of skill in the art would appreciate, the hybrid propulsion aircraft100can be scaled up or down to facilitate a particular purpose based on, for example, flight objective and/or flight plan. Thus, individual ducted fans may be added to, or removed from, the wings to provide the thrust necessary for a given aircraft size. Alternatively, the ducted fans may be enlarged or reduced in size to achieve a targeted thrust power. For example, in certain aspects, the thrust assembly500may be removably configured as modules to enable quick substitution or replacement on the fly.

The hybrid propulsion aircraft100generally comprises a fuselage102, two primary wings104, two canard wings106, and a distributed electric propulsion system, which generates the thrust necessary for flight using a plurality of ducted fans (e.g., primary ducted fans108and canard ducted fans110). For example, as best illustrated inFIGS. 3aand 3b, each wing may be arranged with a plurality of immediately adjacent (i.e., abutting one another) integrated ducted fans across the wingspan of a wing or wing set. Each of the ducted fans generally comprises a thrust assembly500positioned within a duct chamber414, the duct chamber414being defined by the lower and upper primary airfoils302,304and ribs of the primary and canard wings104,106.

In certain aspects, the wings, or portions thereof, may be modular where additional ducted fan modules may be quickly added, removed, and/or substituted (e.g., with a differently rated ducted fan). For example, each ducted fan module may comprise a thrust assembly500and a duct chamber414. A ducted fan module's duct chamber414may be configured to removably couple with an adjacent ducted fan module's duct chamber414(e.g., at the separator plate408). Electrical connectors would be provided to facilitate power transfer between the ducted fan modules. In such an example, the length of the wings may be guided by the number of ducted fan modules employed.

The hybrid propulsion aircraft100further includes landing gear118(e.g., nose-end landing gear and main landing gear), one or more fuel tanks120, an avionics bay122, a payload bay124, a heat exchanger126(e.g., an air-cooled oil cooler with fan), a forward facing air inlet128that supplies air to the engine112, a rear facing engine exhaust nozzle114coupled to the aft end of the engine112that expels exhaust from the engine112, and a power distribution and synchronization avionics module130. The exhaust nozzle114may have a constant area along its length. In lieu of, or in addition to, the landing gear118, the hybrid propulsion aircraft100may employ landing skids.

To provide climate control to the engine bay, one or more cutouts or openings may be provided in the fuselage's102skin (e.g., adjacent the engine112and/or primary generators116). One or more cooling fans may be positioned in the engine bay at each opening and configured to draw air into the engine bay, thereby cooling the engine112, primary generators116, and/or other components. The engine112may include one or more starter batteries to provide a starting current to said engine112upon ignition. The cooling fans also pressurize the engine bay and force air through an exhaust, or gap in the fuselage. The landing gear118may be retractable with a door, thereby reducing drag during horizontal flight.

The hybrid propulsion aircraft's100structure, including the fuselage102and wings104,106, may be fabricated using a composite material (or laminate thereof) including, inter alia, a graphite, fiberglass, or aramid and honeycomb core sandwich construction and connected using metal fittings (e.g., aluminum, titanium, lightweight alloys, etc.). The hybrid propulsion aircraft's100structure may further comprise embedded conductors, which may convey power and/or data signals throughout the hybrid propulsion aircraft100. For example, the embedded conductors may be formed as a conductor sandwich assembly, such as is described in greater detail by commonly owned U.S. Pat. No. 8,937,254, titled “Apparatus and Method for an Aircraft Conductor Sandwich Assembly Embedded to an Aircraft Structure.” Furthermore, these conductors may reside on the outer mold line (OML) of the vehicle to aid in thermal management and use free stream air for cooling. Additionally, the conductors may be placed throughout the aircraft structure to aid in the heating of various components that may require environmental control and/or to provide additional benefits such as de-icing or anti-icing characteristics to the structure of the aircraft accomplished by having the heat generator conductors in close proximity to the surfaces requiring heating.

As best illustrated inFIGS. 1aand 1c, a primary wing104and a canard wing106are positioned on each side of the fuselage102. The two primary wings104, defining a primary wing set, and two canard wings106, defining a canard wing set, are pivotally mounted to the hybrid propulsion aircraft's100airframe (e.g., at the topside of the fuselage102) to provide tilt-wing functionality. For instance, the fuselage102may comprise a plurality of actuator-controlled pivotal connectors802,902, which selectively pivot the primary and canard wings104,106responsive to signals from the flight controller. In certain aspects, the canard wings106may be partially or fully retracted into the fuselage102when not in use or during forward flight.

Each of the two primary wings104is preferably the same length, thereby providing balance to the wing set on each side for the fuselage102. Likewise, each of the two canard wings106is preferably the same length. The primary and canard wing sets may be arranged at an anhedral angle, thereby compensating for, or mitigating, any change in center of gravity and controlling the center of thrust, when the primary and/or canard wing sets are in a vertical wing configuration (e.g., vertical flight mode) or an intermediate tilted wing configuration (e.g., during transition, where the wing is positioned between vertical and horizontal). As is appreciated by those having ordinary skill in the art, an anhedral angle refers to a negative dihedral angle, that is, a downward angle of the wings relative to a horizontal axis. In other aspects, the primary and/or canard wings104,106may be canted.

The two primary wings104of the primary wing set may be fixedly coupled to one another such that they tilt and operate in unison. To that end, as described with regard toFIGS. 6athrough 6c, the two primary wings104may share one or more continuous spars and/or skin panels. Similarly, the two canard wings106may be fixedly coupled to one another as described with regard toFIG. 7. In certain aspects, however, it is contemplated that the tilt of the primary wings104and/or the two canard wings106may be independently controlled. That is, one wing may be tilted at a first angle relative to the fuselage102, while certain of the remaining three wings may be tilted at different angles, thereby improving agility and/or dynamically countering a gust or other outside force.

The distributed electric propulsion system generally comprises an engine112, a gearbox132, one or more primary generators116, and a plurality of ducted fans, each of said plurality of ducted fans being driven by an electric motor. The plurality of ducted fans may include a plurality of primary ducted fans108positioned on the primary wings104and a plurality of canard ducted fans110positioned on the canard wings106. As illustrated, the engine112may be configured to drive a gearbox132. Suitable engines112include, for example, turbo shaft and turbine engines. A turbo shaft engine refers to a gas turbine engine that is optimized to produce shaft power, rather than jet thrust. The engine112may be mounted to, for example, a first bulkhead136, while the gearbox132mounted to a second bulkhead134.

The distributed electric propulsion system uses an all-electric drivetrain. The engine112and the primary generators116are also locally situated, thereby obviating the need for a long driveshaft therebetween, and obviating the need for any driveshaft between the primary generators116and electric motors (which would result in efficiency loss). For example, the engine112and the primary generators116may be directly coupled to the gearbox132. Moreover, because the primary generators116and fan motors506operate in synchronization and at a single voltage and frequency, electronics need not be used between the generator116and the fan motors506to invert or convert the voltage of the power supply or commutate/modulate the frequency. In fact, such electronics would dissipate power, even when electronically efficient components are used. For example, no need exists for brushless motor controllers, rectifiers, DC-DC converters, regulators, etc., which, even assuming efficient electronics, would dissipate some measurable amount of power. However, additional power electronics may be used to provide system benefits such as adjusted power factor, aid in synchronization, or other various benefits at either low powers and voltages or rated voltage and power. While the primary generators116and fan motors506may run at different speeds, depending on the number of poles in the primary generators116and fan motor506(a constant electrical “gear ratio”), the fan motors506run at a substantially constant RPM. Furthermore, the all-electric drivetrain may operate at one frequency, where noise may be filtered out to mitigate electromagnetic interference (“EMI”). Finally, the voltage may be maintained at a constant value throughout the all-electric drivetrain, again, obviating the need to convert the power supply to the ducted fans' motors506.

The gearbox132, in turn, can be coupled with a plurality of generators, including one or more primary generators116(e.g., 1 to 5 generators, more preferably 3 generators) and/or one or more auxiliary power generators1004, which may power onboard accessories or systems. The gearbox132may be further configured to drive other devices, such as a hydraulic pump1010, an oil pump1008, etc. The hybrid propulsion aircraft100may employ a hydraulic system to control, for example, the wing-tilt actuators/motors, the main landing gear actuator(s), nose landing gear actuator(s), the main landing gear brakes, etc.

The primary generators116provide AC power to the plurality of fan motors. Each ducted fan employs a thrust assembly500having a fan motor506, which may vary in size and power rating depending on its position on the hybrid propulsion aircraft100and/or required thrust. One of skill in the art, however, would appreciate that additional, or fewer, primary generators116may be used depending on the desired power or thrust, which is guided by, inter alia, the quantity and/or size of the ducted fans (or motors therein).

According to one aspect, for example, the hybrid propulsion aircraft100may employ 10 to 24, more preferably about 16 to 20, primary ducted fans108and 2 to 16, more preferably 6 to 12, canard ducted fans110. The primary ducted fans108may be about 20 to 40 inches in fan diameter, while the canard ducted fans110may be about 10 to 30 inches in fan diameter. The primary ducted fans108and canard ducted fans110may be evenly spaced along the wingspan, leaving only a nominal gap between fan blade tips (e.g., abutting one another).

To manage the power distribution, the amount of thrust distributed by each of the ducted fans can be varied by pitching the fan blades according to algorithms, which may be executed by flight control computers. That is, through the variable pitch fan blades (e.g., via pitch control mechanism520), the power from each ducted fan may be independently controlled while maintaining the electric motors at the same speed. Accordingly, the operator may individually adjust the thrust at each ducted fan, thereby enabling the operator, whether computer or human controlled, to change the lift distribution across a given wingspan. In other words, the ducted fans may be operated at the same motor speed, but the thrust from each ducted fan may be independently adjusted by changing the pitch of the fans without changing motor speed. The nozzles may be adjusted for efficiency (e.g., control nozzle area) and thrust vectoring. To that end, a thrust nozzle may be positioned at the back of each (aft end) of the ducted fans. The thrust nozzles are adjustable (e.g., via nozzle actuators628and trailing edge control surfaces406) to enable the operator to individually adjust, for example, the thrust vector of each ducted fan and or the thrust itself. With the addition of DC electronics, a similar method could be used with the added utility of controller speed of the fans as well as pitch or just speed with fixed pitch or any combination thereof.

The hybrid propulsion aircraft100may employ a plurality of sensors, in conjunction with the flight controller, to detect and counter any flight anomalies (e.g., gusts, deviation from flight plan, etc.) by adjusting one or more of the adjustable ducted fans and/or adjustable thrust nozzles to reallocate thrust or the direction of thrust as needed. In operation, an operator can operate each piece (e.g., ducted fan) of a wing at its maximum performance condition throughout the vertical, transition, and horizontal flight regimes; thus mitigating lift loss. For example, when encountering flight anomalies, the operator may adjust the thrust to load or unload one or more fan motors to maintain the synchronization of the motors and generators. Moreover, this configuration allows the fan motors506to be driven at the same speed, while providing the operator with the ability to adjust the thrust of a given ducted fan. Indeed, the operator can adjust the thrust along a wingspan to the change lift distribution without changing the fan motor speed, thereby enabling the wing to operate as a lifting propulsion (i.e., the wing can provide both lift and propulsion). As described with regard toFIGS. 5athrough 5c, the operator may also adjust the fan blade pitch to change the thrust. Specifically, the fan blade pitch may be adjusted to increase the efficiency of the hybrid propulsion aircraft100as a whole during various modes of operation. For example, in modes of operation where the hybrid propulsion aircraft100requires less power, the fan blade pitch may be flat pitched such that they draw very little power. As a result and as noted above, the hybrid propulsion aircraft100may generate excess power during modes of operation that require less power, such as horizontal flight mode.

The components of the hybrid propulsion aircraft100are preferably positioned such that the hybrid propulsion aircraft's100center of gravity remains substantially constant, whether the wings are level (horizontal flight position) or up (vertical flight position), and whether the payload bay124and/or fuel tanks120are empty or full. As can be appreciated by those of ordinary skill in the art, the term center of gravity generally refers to a point at which, if the hybrid propulsion aircraft100were suspended, it would be balanced in all positions—i.e., hybrid propulsion aircraft's100hypothetical balancing point in all directions. The center of gravity may be determined using known techniques (e.g., using computer-aided design (CAD) software or using known mathematical equations).

To that end, the fuel tanks120may be distributed to maintain the vehicle's center of gravity. The center of gravity is identified inFIGS. 1fand 1gas COG. For instance, the hybrid propulsion aircraft100may employ a forward fuel tank and an aft fuel tank, each of which may be gravity filled. A transfer pump may be positioned between the two tanks to facilitate center of gravity trimming. The fuel bays may be sealed. Baffles may be installed in the fuel tanks120to mitigate any slosh and fuel starvation issues. Each tank may employ one or more fuel level sensors. For instance, two fuel level sensors may be used per tank for redundancy (i.e., should one fail or otherwise malfunction). A fuel drain can be positioned on the bottom of fuselage102, under the forward tank. Moreover, the payload bay124may be positioned near the hybrid propulsion aircraft's100center of gravity and split (by volume) into two bays along centerline keel. In certain aspects, the payload bay124may house the flight termination system and flight instrumentation.

An opening in the topside of the hybrid propulsion aircraft100receives conductors138from the components (e.g., ducted fans, actuators, etc.) mounted on or in the primary and canard wings104,106. The conductors138from the fan motors506are operatively coupled to the primary generator(s)116positioned within the fuselage102. The conductors138from other electronics (e.g., peripheral avionics, control surface actuators, lights, sensors, etc.) may be operatively coupled to other devices positioned within the fuselage102, such as the primary generators116, the auxiliary power generators1004, and/or other onboard systems or devices.

To increase streamlining and to reduce drag, a removable upper fairing140may be positioned over the opening, conductors138, and other harnessing. Unique generator control and synchronization hardware residing at or near the generators obviates the need for any other power electronics between the generators and the fan motors as the generators drive the motors in a direct line to line fashion. The power may be carried in conductors through Litz wire and/or a metal tube of varying diameter and material for more efficient power transfer, each of which reduces losses associated with AC power, specifically at higher frequencies, due, at least in part to skin effect. A Litz wire comprises a number of individually insulated magnet wires twisted or braided into a uniform pattern, so that each strand tends to take all possible positions in the cross-section of the entire conductor.

An avionics bay122may house the various navigation and flight control systems, which control the various aircraft components and functions. The navigation and flight control systems may be communicatively coupled with an inertial navigation system (“INS”) that is communicatively coupled with an inertial measurement unit and global positioning system (“GPS”) receiver, an onboard data storage device (e.g., hard drive, flash memory, or the like), a wireless communication device, or virtually any other desired services. The GPS gives an absolute drift-free position value that can be used to reset the INS solution or can be blended with it by use of a mathematical algorithm, such as a Kalman Filter. The avionics bay122may also house, for example, an intelligence, surveillance, and reconnaissance (“ISR”) surveillance payload, which may be used to collect data and/or monitor an area. For example, the hybrid propulsion aircraft100may be equipped with one or more cameras, audio devices, and other sensors, especially those requiring large amounts of electric power. Any video, or other data, collected by the hybrid propulsion aircraft100may be communicated to a ground control station in real time wirelessly. The hybrid propulsion aircraft100may be further equipped to store said video and data to the onboard data storage device. In certain aspects, the number of canard ducted fans110may be adjusted to achieve a targeted weight to power ratio. That is, fewer fans and motors may be used in the canard wing106or primary wing104to reduce the overall weight of the hybrid propulsion aircraft100.

FIGS. 3aand 3billustrate, respectively, front and rear isometric views of an arrangement of ducted fans, such as those forming the primarily wing104and the canard wing106. As illustrated, a duct chamber414is defined by a lower primary airfoil302, an upper primary airfoil304, and one or more separator plates408, which are positioned between adjacent thrust assemblies500. The trailing edge of the upper and lower primary airfoils302,304may comprise a plurality of control surfaces406(e.g., ailerons or elevens), which may be independently controlled to adjust the thrust nozzle. For instance, the control surfaces406may be controlled to adjust the thrust nozzle's area (i.e., nozzle area) of a particular ducted fan. That is, the nozzle actuators628(positioned within the separator plates408) may be actuated to drive the control surfaces406, thereby adjusting the nozzle area and thrust vector.

One or more airflow slots402may be positioned at the upper leading edge412of the upper primary airfoil304. The one or more airflow slots402guide airflow into the duct chamber414and toward the thrust assembly500. Each airflow slot402may be selectively sealed/blocked using a slot door410.FIGS. 3cand 3dillustrate the slot doors410in an open position (i.e., allowing airflow through the airflow slot402), whileFIGS. 3eand 3fillustrate the slot doors410in a closed position (i.e., blocking airflow through the airflow slot402). The airflow slots402in the upper leading edge maintain flow attachment inside the duct chamber414in vertical flight mode and at high angle of attack (AoA). Constantly decreasing area through the airflow slot402(i.e., from the inlet to outlet) ensures smooth flow inside airflow slot402. The slot doors410may be lightly sprung to ensure that they close properly for horizontal flight, whereby a pressure differential will pull the slot doors410open when needed for flow control. Finally, the windward leading edge404of the lower primary airfoil302is relatively thick, thus increasing hover and transition performance.

FIGS. 4aand 4billustrate, respectively, side and top cross sectional views of a ducted fan, whileFIG. 4cillustrates a front isometric view of the hybrid propulsion aircraft100. As illustrated, the ratio of the length (C) to diameter (D) of the duct chamber414is relatively short. The ratio may be, for example, between 1.5 and 2.5, more preferably about 2. The performance and geometry of the vehicle are dictated by the ratio of nozzle area (Anozzle) to fan area (Afan) and disc loading. For example, as the nozzle area increases, efficiency at low speed/hover and high speed is improved. For example, area ratio is increased in hover and decreased in high speed forward flight. The control surfaces406have flattened inner surfaces to yield high speed performance, while thick separator plates408allow change in lower area ratios without separation. The separator plates408may comprise a rib covered by a fairing, which may house one or more controllers or actuators (e.g., nozzle actuator628).

FIGS. 5athrough 5cillustrate an example thrust assembly500configured with a pitch control mechanism520.FIG. 5aillustrates a side view of a complete thrust assembly500. The thrust assembly500generally comprises a nacelle502, a rotating fan504, an electric fan motor506, a structural hub508, an aero stator510, and a fairing cone540. The rotating fan504comprises a plurality of fan blades512(e.g.,2to10, more preferably 4 to 7 fan blades512), while the aero stator510comprises a plurality of stator blades514(e.g., 2 to 6, more preferably 4 stator blades514). The electric fan motor506comprises a motor inner and outer iron with magnets (collectively identified as506a) and a motor stator506b. The motor stator506b, which comprises a copper coil, is static (i.e., does not rotate). As illustrated inFIG. 5b, the structural hub508is configured with a plurality of motor securing slots518, each being sized and shaped to receive a stator blade514or portion thereof. The structural hub508bolts the motor stator506bto the aero stator's510stator blades514.

The fan motors506may be brushless direct current (“BLDC”) motors, which have shown to be efficient in the disclosed configuration, but other motor types may be used, including, without limitation, brushless (BL) motors, electronically commutated motors (ECMs or EC motors), brushless electric motor, squirrel cage, induction, brushed, AC motors, etc. In certain aspects, the fan motors506used in the primary ducted fans108are larger than the fan motors506used in the canard ducted fans110.

FIG. 5cillustrates a frontal plan view of a thrust assembly500with the nacelle502removed. The fan blades512are coupled to the rotating hub via a plurality of blade grips516and pitch housing. The pitch of the fan blades512may be dynamically controlled via the pitch control mechanism520, which is illustrated in Detail A. The pitch control mechanism520may comprise a pitch arm524, pitch link526, a torque plate, and a translating pitch cone522.

A pitch arm524extends lengthwise into each of the pitch housings and, when actuated, imparts an axial movement, which causes the blade grip516and fan blade512to axially rotate, thereby changing the pitch. Each pitch arm524is driven by a pitch link526that couples the pitch arm524to the translating pitch cone522. The translating pitch cone522selectively moves laterally toward and away from the hub (direction A), but is spline-guided to rotate with the hub via the rotor pitch mast. In other words, the translating pitch cone522is configured to travel laterally perpendicular with regard to a plane defined by the fan's rotation (plane p). The translating pitch cone522may be laterally driven by a pitch control motor through, for example, a ball screw driven, spline-guided pitch actuation rod, which does not rotate, but imparts a lateral force (in direction A) onto the rotating rotor pitch mast.

In operation, the pitch control motor's shaft rotates, causing the screw driven actuation rod to selectively extend and retract in direction A. The actuation rod causes the translating pitch cone522to correspondingly travel with the actuation rod direction A. As the translating pitch cone522travels, the plurality of pitch links526coupled to the translating pitch cone522also travel in direction A. The pitch links526impart a torsional force onto the pitch arm524, causing it (and the blade grip516) to rotate axially about a pivot point of the fan blade512.

The flight control system can use the pitch control mechanism520to change a fan blade pitch for a given ducted fan, thereby individually controlling the thrust of the ducted fans (and changing the torque and the current needed). To compensate for an increase or decrease in current draw, the fan blades would change pitch accordingly thus loading or unloading the motor as needed to maintain synchronicity. In response, the engine112may be throttled, or otherwise configured, to supply additional torque necessary, while maintaining RPM with the associated generator(s)116. Thus, as long as the fan motors506do not exceed a torque limit, the fan motors506will spin in synchronization with the primary generators116. A plurality of spindle bearings may provide reduced friction between the contact point between the hub and the pitch actuation rod's outer housing. Similarly, spindle bearings may be provided between each blade grip516and pitch housing, to mitigate friction as the fan blades512are pitched (i.e., axially rotated).

FIGS. 6athrough 6cillustrate an example structural layout of a primary wing104, which generally comprises a lower primary airfoil302, an upper primary airfoil304, and a plurality of rib stations626, where the lower primary airfoil302functions as the main structural component. The lower primary airfoil302generally comprises a forward spar602, a mid-spar604, and a lower aft spar606. The upper primary airfoil304comprises an upper leading edge support620and an upper aft spar622. A primary function of the lower aft spar606and the upper aft spar622is to facilitate mounting of trailing edge control surfaces406and stator blades514. When the primary wings104are configured to operate in unison, the forward spar602and the mid-spar604may be continuous through the center section (i.e., the point where the primary wings104pivotally couple to the fuselage102). Structural skin610may be provided on upper and lower side of the lower primary airfoil302, running continuously under the thrust assemblies500.

In one aspect, three ribs may be positioned at each rib station626(e.g., the area between each thrust assembly500), which is ultimately covered with a fairing to define the separator plate408. Two ribs may be provided in the lower primary airfoil302. Specifically, a forward rib614may be positioned between the forward spar602and the mid spar604, while an aft rib616may be positioned between the mid-spar604and the lower aft spar606. The forward rib614and the aft rib616may be positioned under the structural skin610. The third rib, the upper rib618, may couple the lower primary airfoil302to the upper primary airfoil304, while being further configured to define the vertical barrier between adjacent thrust assemblies500. The upper rib618transfers moments from thrust line and upper aileron into the lower spars. The upper leading edge support620may be continuous or discontinuous through the center section, but pinned to the upper rib618at each rib station626to prevent local buckling from wing flexure. The upper leading edge supports620can be loaded as a hoop member from inlet loads. In certain aspects, the upper leading edge supports620may be fabricated as a single component encompassing the arced shape of multiple ducts.

The trailing edge control surfaces406may be actuated to adjust the thrust nozzle at each ducted fan, thereby controlling the roll, yaw, and pitch of the hybrid propulsion aircraft100through differential and/or vectored thrust. The trailing edge control surfaces406are split at each rib station626between adjacent thrust assemblies500. The rib station626may be covered with a fairing to form the separator plate408, thereby providing a hollow space that houses various controllers, sensors, conductors, etc. The trailing edge control surfaces406are held in place using a bearing and pillow block arrangement attached to the intersection of rib and aft spars. The various trailing edge control surfaces406may be ganged together using a torque tube630. Actuators628are connected to one or more ribs at a rib station626(e.g., hidden in the space defined by the fairing). Each actuator628is coupled with a push arm632, which is attached to a torque tube630for a given control surface406. Thus, each control surface406may be separately and independently controlled by selectively actuating a given actuator628.

FIG. 7illustrates an example structural layout of a canard wing106, which is structurally similar to the primary wing104, but scaled down, therefore requiring fewer structural components. The lower canard airfoil710functions as the main structural component, and comprises a forward tube spar702and a lower aft spar704. The upper canard airfoil712comprises an upper leading edge support706and an upper aft spar708. The lower aft spar704and the upper aft spar708are discontinuous through the center section to facilitate mounting of trailing edge control surfaces406and stator blades514. The upper canard airfoil712is pinned to a rib at each rib station to prevent local buckling from wing flexure. Structural skin may be provided on the upper and lower sides of lower canard airfoil710, running continuously under the thrust assemblies500. A canard rib714is positioned at each rib station (e.g., the area between each thrust assembly500). The canard rib714couples the lower canard airfoil710to the upper canard airfoil712, while being further configured to define a vertical barrier between adjacent thrust assemblies500. The canard rib714transfers moments from thrust line and upper aileron into the lower spars. The trailing edge control surfaces406operate in substantially the same manner as discussed with regard to the primary wing104inFIG. 6c.

FIG. 8illustrates an example primary wing pivot configuration800for pivotally connecting the primary wing104to the fuselage102. The primary wing104may be pivotally connected to the fuselage102using a plurality of pivotal connectors802, which may be actuator-controlled. Suitable actuators include, without limitation, hydraulic actuators, electric actuators, or a hydraulic or electrically driven translating jackscrew. As illustrated, the various conductors804egress from the primary wing104at the mid-spar604close to the primary wing pivot point. The conductors804couple to the power distribution system via a conductor opening in the surface of the fuselage102. Positioning the conductors804at the primary wing pivot point minimizes conductor sweep, thereby mitigating risk of damage to the conductors804. In operation, the primary wing can rotate from a hover position to a horizontal flight position within 10 seconds or less.

FIGS. 9aand 9billustrate an example canard pivot configuration900for pivotally connecting the canard wing106to the fuselage102. The canard wing106may be pivotally connected to the fuselage102using a plurality of pivotal connectors902, which, like the pivotal connectors802ofFIG. 8, may be actuator-controlled. For example, the pivotal connectors902may be pillow block bearing fittings910that attach forward tube spar702to the airframe of the fuselage102. A linear actuator mechanism914rotates the canard wing's106forward tube spar702via a control horn912. The conductors904may be arranged in service loops, which contract and expand in diameter as the forward tube spar702rotates. Such service loops mitigate kinking while preventing loose or unfastened cabling. For example, four forward service loops906and five aft service loops908may be positioned one each side of the forward tube spar702. The conductors904may travel toward the aft end of the hybrid propulsion aircraft100, where the conductors904may couple to the hybrid propulsion aircraft100through a single conductor opening, along with the conductors804for the primary wing104, thereby minimizing the number of openings in the fuselage102.

While each of the primary wings104and the two canard wings106are illustrated as pivoting in their entirety relative to the fuselage102(between the vertical wing configuration and the horizontal wing configuration), it is contemplated that only a portion of the primary wings104and/or the two canard wings106may pivot relative to the fuselage102. For example, the primary wings104and/or the two canard wings106may be fabricated with a fixed wing portion (e.g., a fixed leading edge portion) and a hinged wing portion (e.g., a pivoting trailing edge portion where the hinge runs lengthwise like a flap) having positioned thereon the plurality of ducted fans108,110to generate an aggregate thrust. In this example, the hinged wing portion would be controlled and pivoted to direct the aggregate thrust from the ducted fans108between the vertical wing configuration in hover mode and the horizontal wing configuration in horizontal flight mode. In certain aspects, each of the plurality of ducted fans108may be individually controlled in terms of thrust/speed, as well as pivot angle (relative to the wing104or other ducted fans108). For example, each of the plurality of ducted fans108,110may pivot relative to the fuselage102independently from one or more of the remaining ducted fans108,110.

FIGS. 10aand 10billustrate, respectively, front and rear isometric views of the gearbox132coupled with multiple primary generators116, multiple auxiliary power generators1004, one or more oil pumps1008, and one or more hydraulic pumps1010. In operation, the gearbox132receives a rotational input from the engine112via an input driveshaft1002. The gearbox132allocates the rotational input to the plurality of primary generators116, one or more auxiliary power generators1004, and, when applicable, the oil pumps1008and the hydraulic pumps1010. One or more generator control and synchronization units (GCSUs)1006are provided to provide basic control, monitoring, and protection of the three primary generators while also allowing for low speed startup and synchronization of motors to the generator. Other generator control units provide basic control, monitoring, and protection to the generator116and two auxiliary power generators1004. The hydraulic pump1010may be used to operate the wing tilt actuators (e.g., for the primary wing104and canard wing106), as well as the landing gear actuators, and brakes.

FIG. 11illustrates an electrical mapping diagram1100of fan motors506that allows for a sustainable asymmetric thrust in the event of a conductor or generator116failure. In other words, failure tolerance is accomplished by controlling the reallocation of power through distributed propulsion. As illustrated in the electrical mapping diagram1100, in an arrangement having 18 primary ducted fans108and 6 canard ducted fans110, each of the three primary generators116(i.e., G1, G2, G3) powers an equal number of equally distributed primary fan motors506(i.e., primary motors1through18) and canard fan motors506(i.e., canard motors1through6). That is, the fan motors506driven by a given generator are evenly distributed across a given wing's104,106wingspan such that thrust is balanced on each side of the fuselage102. For example, a first generator (G1)116may power canard motors3and6, as well as primary motors1,6,7,10,14, and17. The remaining motors are evenly divided between second generator (G2)116and third generator (G3)116. Specifically, the second generator (G2)116may power canard motors1and4and primary motors2,5,9,12,13, and18, while the third generator (G3)116may power canard motors2and5and primary motors3,4,8,11,15, and16. Thus, if any one of the first through third generators (G1-G3)116were to fail, the remaining motors would be evenly distributed and the hybrid propulsion aircraft100would remain balanced to mitigate any rolling moment. While not illustrated, the hybrid propulsion aircraft100may further comprise one or more battery banks to store power generated by the one or more generators116. The one or more battery banks may be used to power the primary ducted fans108and/or the canard ducted fans in the event of engine112failure. The one or more battery banks may employ, for example, lithium iron phosphate batteries. As can be appreciated, AC power generated by the one or more generators116may first be converted to DC via a rectifier before being transferred to said one or more battery banks, in which case a motor controller or inverter can be used to drive the motor using the DC power.

In certain aspects, the ducted fans may employ counter-rotation ordering and loads. For example, one ducted fan may rotate clockwise, while the two adjacent ducted fans rotate counter-clockwise. Similarly, ducted fans positioned on one side of the fuselage102may counter-rotate with regard to the ducted fans positioned on the opposite side of the fuselage102. While the example electrical mapping diagram1100employs 18 primary ducted fans108and 6 canard ducted fans110, the same principles of maintaining an equal load and even distribution may be applied to countless arrangements having varying quantities of fan motors506, such as the arrangement ofFIG. 1a, which has 18 primary ducted fans108and 12 canard ducted fans110.

FIG. 12illustrates a synchronization monitoring system1200having a flight control unit (“FCU”)1202that prevents one fan motor506from falling out of synchronization with the other fan motors506and generator116. In summary, the FCU1202detects whether a fan is, or will soon be, out of synchronization through, for example, torque or current detection, waveform analysis, and comparing the phase angles of two signals. Blade pitch may be adjusted to increase or decrease a given load on the fan motor506, while a turbine speed regulator maintains constant speed. The FCU1202accomplishes this by monitoring the motor voltage (via voltage sensor1206) and motor current (via current sensor1204), closing the fan pitch loop to achieve the autopilot's commanded pitch, reducing pitch (and notifying the autopilot) if the torque approaches a predetermined limit, and providing fan motor parameters including, inter alia, current and voltage phasors, rotations per minute (“RPM”), fan speed, temperatures, pitch, etc. to the flight controller and/or GSCU1006. Indeed, the phase angle between voltage and current may be used to predict loss of synchronization between the fan motor506and/or generator116, thus enabling use of a low-risk, off the shelf hardware in lieu of custom hardware. Synchronization may be achieved by regulating the GCSU1006during low speed startup of the generator. For example, the FCU1202could configure the fan blades512with a flat pitch to reduce load on the motor506during startup. As the motors506begin to spin with the generator116, the blade pitch can be gradually increased. In certain aspects, the load on the motor506may be increased with each RPM to provide a more stable and robust synchronization. The FCU may also control a circuit breaker or other electronic device to de-couple a motor (e.g., a malfunctioning or defective motor) from the bus to protect the system. Additionally, the FCU may provide command and control of various power electronics that augment the electrical operation of the fan ranging from start up through normal operation including the ability to provide modal damping, braking, or temporary power boosts from a secondary power bus.

The above-cited patents and patent publications are hereby incorporated by reference in their entirety. Although various embodiments have been described with reference to a particular arrangement of parts, features, and like, these are not intended to exhaust all possible arrangements or features, and indeed many other embodiments, modifications, and variations will be ascertainable to those of skill in the art. Thus, it is to be understood that the invention may therefore be practiced otherwise than as specifically described above.