Aircraft

Abstract

An aircraft capable of vertical takeoff and landing, hovering, and efficient forward flight is described. The aircraft includes two laterally mounted tiltable propellers and a central rotor positioned above the propellers. The propellers are tiltable between at least a horizontal position for forward flight and a vertical position for vertical or hovering flight. The central rotor can be powered for vertical and transient flight modes and can rotate by freewheeling during forward flight. The propellers can be tilted differentially during vertical or hovering flight to counteract torque effects of the central rotor. The central rotor can be foldable and / or easily removable from the aircraft for ease of storage and transportation.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Application No. 62 / 886,578, entitled "AERIAL VEHICLE," filed August 14, 2019, U.S. Provisional Application No. 62 / 896,257, entitled "AERIAL VEHICLE," filed September 5, 2019, and U.S. Provisional Application No. 63 / 018,848, entitled "AERIAL VEHICLE," filed May 1, 2020, all of which are incorporated by reference in their entirety for all purposes.

[0002] [Field of the Invention] FIELD OF THE DISCLOSURE This disclosure relates generally to manned or unmanned aerial vehicles, and more specifically to aerial vehicles capable of vertical and horizontal flight. [Background technology]

[0003] A helicopter is an aircraft in which lift and thrust are provided by one or more horizontal rotors. Advantages of helicopters include their ability to hover and take off and land vertically. However, helicopters suffer from, among other things, their relatively low operating energy efficiency compared to fixed-wing aircraft.

[0004] A gyroplane (also known as a gyrocopter or autogyro) is an aircraft that uses an unpowered rotor to generate lift by spinning on its own axis. Autogyro is a rotor condition in which the rotor gets 100% of the power required to spin from the freestream, and the resulting rotation provides lift. In a gyrocopter, forward thrust is usually provided by an engine-driven propeller. However, like fixed-wing aircraft, gyrocopters cannot take off and land vertically.

[0005] In the case of a gyroplane, as the aircraft descends onto the runway and gains speed, the shaft of the overhead rotor is tilted backward, allowing the wind to blow through the rotor and begin to spin. When the rotor reaches a certain RPM, it becomes a "virtual wing" for the gyrocopter to provide lift. Once the desired RPM is reached, the gyrocopter is ready to take off. As the gyrocopter gains speed in the air, the angle of attack of the rotor head (virtual wing) is reduced by moving the shaft forward, increasing speed and reducing drag. Gyrocopters do not have a variable pitch rotor, so they do not have the ability to achieve a vertical takeoff. The pitch of the blades of a gyrocopter is usually zero. In addition to being able to tilt the shaft back and forth, gyrocopters can also tilt the shaft / rotor head to the right and left, providing aileron-like maneuverability. Also, to ensure the gyrocopter flies stably, it has a unique rotor head assembly that can teeter the shaft, allowing the blades to move freely as they spin.

[0006] A helicopter has a fixed vertical shaft with a swashplate and a link to the rotor head, allowing the pilot to vary the pitch of the rotor blades to generate lift, and a propeller mount mounted vertically at the end of the boom (or ducted fan) to generate thrust to counter the torque generated by the motor driving the rotor head.

[0007] In a helicopter, the blades move air downwards, creating thrust and lift, while in a gyrocopter, air flows upwards through the blades, spinning the blades and creating lift. Summary of the Invention

[0008] The systems, methods, and apparatus of the present technology each have several innovative aspects, no single one of which is solely responsible for its desirable attributes disclosed herein, and without limiting the scope of this disclosure, its more prominent features will now be discussed briefly.

[0009] In a first aspect, an aircraft includes a fuselage, a mast extending upwardly from the fuselage, the mast secured to the fuselage at a lower end of the mast, a rotor rotatably coupled to an upper end of the mast opposite the lower end, a rotor motor disposed at the upper end of the mast and configured to rotate the rotor in a first direction, a lateral boom coupled to an intermediate section of the mast between the upper end and the lower end, a first powered prop-rotor disposed at a first end of the lateral boom, a second powered prop-rotor disposed at a second end opposite the first end of the lateral boom, a first prop-rotor tilt servo configured to control an attitude of the first powered prop-rotor between at least horizontal and vertical tilt angles, and a second prop-rotor tilt servo configured to control an attitude of the second powered prop-rotor between at least horizontal and vertical tilt angles independent of an attitude of the first powered prop-rotor.

[0010] In some embodiments, the first powered propeller rotor is powered by a first propeller rotor motor and the second powered propeller rotor is powered by a second propeller rotor motor, and the rotational speeds of the first propeller rotor motor and the second propeller rotor motor are independently variable. In some embodiments, the first and second propeller rotor motors are configured to counteract the torque effect of the rotor motors during vertical or hovering flight by powering the first and second propeller rotors at different speeds. In some embodiments, the output of the rotor motor is rotationally coupled to the rotor by a one-way bearing that transfers torque from the rotor motor to the rotor when the rotor motor is activated and allows the rotor to rotate freely in the first direction when the rotor motor is deactivated. In some embodiments, the first and second propeller rotor tilt servos are configured to control the attitude of the first and second powered propeller rotors within a tilt angle range of more than 90 degrees. In some embodiments, the tilt angle range is about 150 degrees. In some embodiments, the first and second powered prop rotors are tiltable between a first extreme tilt angle at least 25 degrees aft from vertical and a second extreme tilt angle at least 25 degrees below horizontal. In some embodiments, the first extreme tilt angle is at least 30 degrees aft from vertical and the second extreme tilt angle is at least 30 degrees below horizontal. In some embodiments, the aircraft further includes a rotor tilt servo configured to tilt the rotors between at least a first tilt angle at which the rotors rotate about a vertical axis of the aircraft and a second tilt angle at which the rotors rotate about an axis angled at about 20 degrees relative to the vertical axis of the aircraft. In some embodiments, the first and second prop rotor tilt servos are configured to counteract torque effects of rotor motors during vertical or hovering flight by differentially tilting the first and second powered prop rotors relative to the vertical axis of the aircraft.In some embodiments, the aircraft is configured to fly in a plurality of flight configurations, including a vertical flight configuration in which the first and second powered propeller rotors are positioned within 30 degrees of the vertical and the rotors are driven by rotor motors, and a horizontal flight configuration in which the first and second powered propeller rotors are positioned within 30 degrees of the horizontal and the rotors rotate by free rotation. In some embodiments, the rotors include rotor blades configured to automatically adjust to a positive blade pitch in the vertical flight configuration and to a flat blade pitch in the horizontal flight configuration. In some embodiments, the aircraft further includes a tiltable tail including a horizontal stabilizer, the tiltable tail configured to rotate about a longitudinal axis of the horizontal stabilizer. In some embodiments, the tiltable tail is configured to rotate to a lowered position during vertical flight such that the horizontal stabilizer is aligned with downwash generated by the rotor when the rotor motor is operating.

[0011] In a second aspect, an aircraft includes a rotor including a plurality of rotor blades, a lower rotor hub, and an upper rotor hub assembly including at least one mounting member, the lower rotor hub including a rotor mount shaft extending along a rotational axis of the rotor and at least one mounting pin hole extending through the rotor mount shaft, each mounting member including a center section having two mounting pin holes extending therethrough that allow the center section to be coupled to the lower rotor hub by inserting mounting pins into the two mounting pin holes in the center section, and two mounting brackets disposed at opposite ends of the center section, each mounting bracket fixedly coupled to one of the plurality of rotor blades.

[0012] In some embodiments, the upper rotor hub assembly further includes a blade pitch adjustment linkage configured to automatically adjust the blade pitch of the rotor blades based on the rotational speed of the rotor. In some embodiments, the blade pitch adjustment linkage includes at least one biasing element configured to cause an increase in blade pitch when subjected to an increased centrifugal force associated with an increase in the rotational speed of the rotor. In some embodiments, the biasing element includes a gas spring coupled to the center section and one of the two mounting brackets. In some embodiments, each mounting bracket of each mounting member is coupled to the center section by a hinge to enable folding of the mounting member between an extended configuration and a folded configuration, each mounting bracket further includes a plurality of locking pin holes, the plurality of locking pin holes configured to lock the mounting member in the extended configuration when the locking pin is disposed within the locking pin hole. In some embodiments, each mounting member can be teetered about the mounting pin. In some embodiments, the aircraft includes at least four blades and at least two mounting members, each mounting member coupled to two oppositely disposed rotor blades of the plurality of rotor blades, each mounting member shaped to allow independent teetering of at least one other mounting member. In some embodiments, each rotor blade is slidably mountable and removable from a mounting bracket. In some embodiments, each mounting bracket of each mounting member is attached to a mounting body sized and shaped to fit within a mounting body opening of the mounting member, the mounting body being securable to the mounting member by inserting a blade mounting pin into a pin hole in the mounting member and the mounting body.In some embodiments, the upper rotor hub assembly further includes an upper rotor mount hub including a tubular shaft at least partially surrounding a rotor mount shaft of the lower rotor mount hub, each mounting member being coupled to the upper rotor mount hub by at least one mounting pin, and the tubular shaft being removably coupled to the lower rotor mount shaft by at least one mounting pin.

[0013] In a third aspect, a rotor assembly for an aircraft includes a plurality of rotor blades and an upper rotor hub assembly including at least one mounting member, each mounting member including a center section, two mounting brackets disposed at opposite ends of the center section, each mounting bracket fixedly coupled to one of the plurality of rotor blades, and a blade pitch adjustment linkage coupled to the mounting brackets and the center section, the blade pitch adjustment linkage configured to automatically adjust the blade pitch of the rotor blades based on a rotational speed of the rotor blades.

[0014] In some embodiments, the blade pitch adjustment linkage includes at least one biasing element configured to cause an increase in blade pitch when subjected to an increase in centrifugal force associated with an increase in rotational speed of the rotor blades. In some embodiments, the biasing element includes a gas spring coupled to the center section and to one of the two mounting brackets. In some embodiments, the blade pitch adjustment linkage includes at least one synchronizing linkage coupled to the mounting bracket and configured to synchronize the blade pitch of the rotor blades.

[0015] In a fourth aspect, a rotor assembly for an aircraft includes first and second rotor blades and a mounting member to which the first and second rotor blades are coupled in an opposing arrangement, the mounting member including a center section including a pivot coupler configured to enable the mounting member and the rotor blades to be teetered relative to the aircraft, two mounting brackets disposed at opposite ends of the center section, each mounting bracket fixedly coupled to the first and second rotor blades, and a blade pitch linkage coupled to the mounting brackets and the center section, the blade pitch linkage configured to synchronize pitch angles of the first and second rotor blades.

[0016] In some embodiments, the rotor assembly includes first and second inner cylinders extending from the central section, the mounting bracket includes first and second outer cylinders that slidingly receive the first and second inner cylinders, the outer cylinders include pin-receiving openings, the inner cylinder includes openings that define a track, and the blade pitch linkage includes pins that extend through the openings in the first and second cylinders such that as the outer cylinder slides relative to the inner cylinder, the pins slide through the track, thereby causing rotation of the outer cylinder relative to the inner cylinder. [Brief description of the drawings]

[0017] The above aspects, as well as other configurations, aspects, and advantages of the present technology, will now be described in connection with various implementations with reference to the accompanying drawings. The illustrated implementations are merely examples and are not intended to be limiting. Throughout the drawings, like numerals typically identify like components unless the context dictates otherwise.

[0018] [Figure 1] 1 illustrates an isometric view of an aircraft in accordance with an exemplary embodiment of the present technology;

[0019] [Diagram 2] FIG. 2 shows a side view of the aircraft of FIG. 1.

[0020] [Diagram 3] FIG. 3 shows a rear isometric view of the aircraft of FIGS. 1 and 2.

[0021] [Figure 4] FIG. 4 shows a top front view of the aircraft of FIGS. 1 to 3.

[0022] [Diagram 5] 2 illustrates a schematic of an exemplary propeller tilt range relative to a lateral boom of an exemplary aircraft;

[0023] [Figure 6] 1A-1C are schematic diagrams illustrating exemplary VTOL / hover and forward flight tilt positions of the propeller.

[0024] [Figure 7] 1 illustrates a mid-section of an exemplary aircraft lateral boom including a propeller support and control components disposed thereon.

[0025] [Figure 8] FIG. 8 is a detailed view of certain propeller support and control components of FIG.

[0026] [Figure 9] 9 illustrates the intermediate and lateral sections of the exemplary aircraft lateral boom of FIGS. 7 and 8, including the propeller support and control components disposed thereon.

[0027] [Figure 10] FIG. 10 illustrates a lateral portion of the exemplary aircraft lateral boom of FIGS. 7-9, including the propeller support and the control components disposed thereon.

[0028] [Figure 11] 1 illustrates a side view of an exemplary aircraft lower rotor hub.

[0029] [Figure 12] 12 illustrates a rear view of the lower rotor hub of the exemplary aircraft of FIG. 11.

[0030] [Figure 13] FIG. 13 illustrates a top perspective view of the lower rotor hub of the exemplary aircraft of FIGS. 11 and 12.

[0031] [Figure 14] FIG. 14 illustrates a side view of the lower rotor hub of the exemplary aircraft of FIGS. 11-13 in a vertical configuration.

[0032] [Figure 15] FIG. 15 illustrates a side view of the exemplary aircraft lower rotor hub of FIGS. 11-14 in a tilted configuration.

[0033] [Figure 16] 16 illustrates an upper rotor hub assembly including two mounting members connectable to the lower rotor hub of FIGS. 11-15.

[0034] [Figure 17] 1 illustrates a rotor blade attached to a blade arm of a mounting member in accordance with an illustrative embodiment; [Figure 18] 1 illustrates a rotor blade attached to a blade arm of a mounting member in accordance with an illustrative embodiment;

[0035] [Figure 19] 1 illustrates the upper rotor hub assembly in a folded configuration. [Figure 20] 1 illustrates the upper rotor hub assembly in a folded configuration.

[0036] [Figure 21]FIG. 21 shows a partial isometric view of the upper rotor hub assembly of FIGS. 16-20 coupled to the lower rotor hub of FIGS. 11-15.

[0037] [Figure 22] 21 shows a partial top view of the upper rotor hub assembly of FIGS. 16-20 coupled to the lower rotor hub of FIGS. 11-15.

[0038] [Diagram 23] 1 illustrates a perspective view of a portion of an upper rotor hub assembly according to some embodiments.

[0039] [Figure 24] 24 illustrates a side view of a portion of the upper rotor hub assembly of FIG. 23 coupled to a lower rotor hub of an exemplary aircraft.

[0040] [Diagram 25] 1 illustrates an exemplary embodiment of an upper rotor hub assembly with a bayonet-type blade attachment system. [Figure 26] 1 illustrates an exemplary embodiment of an upper rotor hub assembly with a bayonet-type blade attachment system.

[0041] [Figure 27] 1 illustrates an exemplary embodiment of a rotor hub assembly including a teetering pivot point.

[0042] [Figure 28] 28 shows a side view and a cross-sectional view of the rotor hub assembly of FIG. 27 in a zero pitch configuration. [Figure 29] 28 shows a side view and a cross-sectional view of the rotor hub assembly of FIG. 27 in a zero pitch configuration.

[0043] [Diagram 30] 20 shows side and cross-sectional views of the rotor hub assembly of FIGS. 27-29 in a positive pitch configuration. [Diagram 31] 20 shows side and cross-sectional views of the rotor hub assembly of FIGS. 27-29 in a positive pitch configuration.

[0044] [Diagram 32] FIG. 32 shows an exploded view of the rotor hub assembly of FIGS. 27-31.

[0045] [Diagram 33] 33 illustrates an exemplary gearing system for rotating the upper rotor hub assembly of FIGS. 27-32.

[0046] [Diagram 34] FIG. 33 is a cross-sectional view showing a braking system for slowing down the rotational speed of the upper rotor hub assembly of FIGS. 27-32.

[0047] [Diagram 35] 1 illustrates an exemplary aircraft including a tiltable tail. [Diagram 36] 1 illustrates an exemplary aircraft including a tiltable tail. [Figure 37] 1 illustrates an exemplary aircraft including a tiltable tail.

[0048] [Figure 38] 1 illustrates an exemplary aircraft including a single propeller and pivotable wings configured to act as control surfaces. [Figure 39] 1 illustrates an exemplary aircraft including a single propeller and pivotable wings configured to act as control surfaces. [Diagram 40] 1 illustrates an exemplary aircraft including a single propeller and pivotable wings configured to act as control surfaces. [Diagram 41] 1 illustrates an exemplary aircraft including a single propeller and pivotable wings configured to act as control surfaces. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Generally described, embodiments of the present disclosure provide aircraft and aircraft systems, components, and control methods that provide enhanced flight characteristics compared to existing helicopters, gyroplanes, fixed-wing aircraft, and tiltrotor aircraft. The aircraft disclosed herein may enable efficient forward flight, hovering, and / or vertical takeoff and landing (VTOL), as well as transitions between flight modes during flight. For example, an aircraft according to the present technology may be able to take off vertically from a deployment site, transition to a forward flight mode for near-horizontal flight to a remote location, transition to a vertical flight mode for hovering at the remote location for an extended period of time, transition to a forward flight mode for near-horizontal flight to a landing site (e.g., a deployment site), and transition back to a vertical flight mode to land at the landing site. Thus, the present disclosure provides an aircraft capable of extended data collection or observation at relatively remote locations beyond the range of conventional helicopters without requiring a runway for takeoff and landing.

[0050] Some of the aircraft described herein may be further configured to be partially disassembled and may include foldable components to provide a more compact configuration for transportation to or from the deployment location. In one example, the central rotor of the aircraft may include one or more pairs of blades attached to an upper rotor hub assembly. The upper rotor hub assembly may be removable from the lower rotor hub of the aircraft and may allow the rotor blades to be folded into a substantially parallel configuration such that the central rotor may be transported in a container of approximately the same length as the individual rotor blades without the need to individually separate the rotor blades from the upper rotor hub assembly. When the aircraft is to be deployed again, the central rotor may be conveniently deployed and attached to the lower rotor hub without the need for additional calibration, alignment, etc.

[0051] 1-4 illustrate an exemplary aircraft 100 configured for in-flight transitions between vertical and horizontal flight modes. The aircraft 100 includes a fuselage 102, a mast 120 extending generally upwardly from the fuselage 102, and a tail section 150 disposed aft of the fuselage 102. A tiltable central rotor 140 is rotatably coupled at an upper end of the mast 120. Tiltable mounted prop rotors 136l, 136r are rotatably coupled at opposite ends of a boom 132 extending laterally from the mast 120.

[0052] The fuselage 102 is the body section of the aircraft 100 and may include an interior volume sized and shaped to hold a payload. For example, the interior volume of the fuselage 102 may be used to accommodate one or more items being transported by the aircraft 100. In some embodiments, the fuselage 102 may include one or more reconnaissance or surveillance devices, such as imaging devices (e.g., visible light cameras, infrared cameras, thermal cameras, still cameras, video cameras, synthetic aperture radar, etc.), listening devices, or communications devices, etc. The fuselage 102 may further include at least some of the control systems for the aircraft 100, such as motor, control surface, or tilt servo controllers, an autopilot system, etc. If the aircraft 100 is configured to operate as a remotely piloted unmanned aerial vehicle (UAV) or drone, the fuselage 102 may also include a communications system for receiving control commands from a remote pilot. The undercarriage 104 may be located on the sides or bottom of the fuselage 102 for use during the takeoff and landing phases of flight and may include wheeled landing gear, skids, and / or any other suitable type of undercarriage. The fuselage 102 and undercarriage 104 may comprise any suitably rigid or semi-rigid material, such as, for example, metal, plastic, carbon fiber, wood, fiberglass, etc.

[0053] The mast 120 extends generally upward from the fuselage 102 and supports a central rotor 140 disposed at an upper end of the mast 120. In some embodiments, for example, in the embodiment shown in Figures 1-4, the mast also includes a forward tilt such that the mast extends upward from the fuselage 102 at a forward angle. As shown in Figure 2, the forward tilt of the mast 120 may advantageously allow the axis of rotation of the central rotor 140 to be aligned with the center of gravity of the fuselage 102. Also, when the propeller rotors 136l, 136r are tilted upward for vertical / hovering flight, the longitudinal positions of the central rotor 140, the propeller rotors 136l, 136r, and the center of gravity of the fuselage 102 are all aligned with a common center of gravity for improved stability in hovering or vertical flight. The mast 120 may also serve as a central attachment point for other components of the aircraft 100, including the boom 132, the tail 150, and the lower rotor hub 300. The mast 120 may further include an interior volume within which one or more aircraft components may be disposed. In some embodiments, an energy storage medium, such as batteries, hydrogen storage devices, etc., may be included within the mast 120. Locating batteries or hydrogen storage devices within the mast 120 may advantageously keep such relatively heavy components closer to the center of gravity of the aircraft 100, thereby improving stability.

[0054] The central rotor 140 is rotatably mounted to the top of the shaft 120 via a lower rotor hub 300. The rotor blades 142 are secured to an upper rotor hub assembly 400 that is coupled to the lower rotor hub 300. The rotor blades 142 may have an airfoil profile configured to enhance lift generation while the central rotor 140 is rotating. The rotor 140 of the exemplary aircraft of FIGS. 1-4 has four rotor blades 142, although it will be understood that other numbers of rotor blades 142 may be included. For example, in some embodiments, the rotor 140 may have two, three, four, five, six, or more rotor blades 142.

[0055] The lower rotor hub 300 is tiltably mounted to an upper portion of the mast 120, e.g., to a central rotor control housing 122. The central rotor control housing 122 can include one or more servos configured to provide at least fore-aft tilt of the central rotor 140 (e.g., by tilting the lower rotor hub 300). In some embodiments, the central rotor control housing 122 further includes one or more servos configured to provide lateral tilt of the central rotor 140. The central rotor control housing 122 can also include a rotor motor configured to rotate the central rotor 140 during some phases of flight (e.g., during vertical and / or transitional flight modes), as described in more detail below. In some embodiments, the rotor motor can be configured to rotate the central rotor 140 at a rotational speed up to a typical gyroplane rotor rotational speed (e.g., up to about 200-600 rpm), which is slower than a typical helicopter rotor rotational speed (e.g., about 400-1500 rpm or more). The rotor motor may be rotationally coupled to the central rotor 140 by a clutch and / or a one-way bearing so that during forward flight, the central rotor 140 may rotate faster than the rotor motor and the central rotor 140 may continue to rotate by autorotation when the rotor motor is not rotating.

[0056] The prop rotors 136l, 136r are configured to provide lift and / or forward thrust in response to tilting of the prop rotors 136l, 136r. The prop rotors 136l, 136r are tiltably mounted on opposite ends of the boom 132. In some embodiments, the boom 132 includes distal arms 134l and 134r that are individually pivotable along a lateral axis of the boom, such that each prop rotor 136l, 136r is independently tiltable by pivoting the distal arms 134l, 134r of the boom 132. Servos and / or other actuators disposed within the prop rotor tilt control housing 130 can control the pivoting of the distal arms 134l, 134r. As described in more detail below, each prop rotor 136l, 136r can be independently powered by left and right prop rotor motors and can be operated at different relative speeds to enhance maneuverability. The speed of both propeller rotors 136l, 136r may be further adjusted collectively to propel the aircraft forward through a desired range of speeds. In some embodiments, the propeller rotors 136l, 136r may have blades that feature a hybrid shape between a propeller shape and a rotor shape to operate efficiently in both forward and vertical / hover flight modes.

[0057] The tail section 150 is attached to the rear of the aircraft 100 and includes a horizontal stabilizer 152 and a vertical stabilizer 154. A vertical stabilizer 156 may secure the tail section 150 to the mast 120 or the fuselage 102. The horizontal stabilizer 152 and the vertical stabilizer 154 provide stability to the aircraft primarily during horizontal flight. In some embodiments, the tail section 150 may include one or more control surfaces, such as an elevator disposed on the horizontal stabilizer 152 and / or a rudders disposed on the vertical stabilizer 154. In embodiments having a rudders on the vertical stabilizer 154, the vertical stabilizer 154 may be positioned in a position within the slip stream of the propeller rotors 136l, 136r to increase the effectiveness of the rudders at low airspeeds.

[0058] With reference to Figures 5 and 6, and continuing reference to Figures 1-4, an exemplary flight control system and method will now be described. Figure 5 illustrates generally an exemplary tilt range of the prop rotors 136l, 136r relative to the lateral boom 132 of the aircraft 100. Figure 6 illustrates generally an exemplary VTOL / hover and forward flight tilt positions of the prop rotors. Each of the prop rotors 136l, 136r may have a range of tilt angles of at least 90 degrees, and in some cases up to 150 degrees or more. For example, the prop rotors 136l, 136r may be tiltable for a VTOL / hover position or range of positions, with each prop rotor 136l, 136r substantially aligned about a vertical or z-axis to generate upward lift. The proprotors 136l, 136r may further be tiltable to a forward flight or horizontal flight position or range of positions, with each proprotor 136l, 136r substantially aligned about a longitudinal or x-axis to generate forward thrust. In either the VTOL / hover position or the forward flight position, each proprotor 136l, 136r may be independently tiltable within a range of about 15 degrees, 20 degrees, 25 degrees, 30 degrees, or more, for maneuvering and / or stability, etc., as described below. In some embodiments, the proprotors 136l, 136r may be tilted to any tilt angle between 30 degrees below the horizontal and 30 degrees aft from the vertical, for a total tilt angle range of about 150 degrees.

[0059] Vertical flight modes, such as VTOL, hovering, etc., can be achieved with the propellers 136l, 136r in a VTOL / hovering position, such that the rotational axis of each of the propellers 136l, 136r is within about 30 degrees of vertical. In the VTOL / hovering position, the spinning propellers 136l, 136r generate primarily upward lift. The central rotor 140 can also be used during vertical flight modes. The central rotor 140 is maintained in a substantially vertical attitude, provides gyroscopic stabilization for the aircraft 100, and can be rotated by the rotor motors at a speed sufficient to generate additional lift in addition to the lift provided by the propellers 136l, 136r. For example, spinning the central rotor 140 at a relatively low rotational speed (e.g., a typical gyroplane rotor rotational speed) can be sufficient to significantly stabilize the aircraft 100. However, in addition to stabilizing the aircraft 100, the central rotor 140 when powered may also produce torque effects and gyroscopic precession. In some embodiments, the prop rotors 136l, 136r may be differentially controlled and / or configured to rotate in a direction opposite to that of the central rotor 140 to counteract the torque effects of the central rotor 140. For example, the torque generated by the central rotor 140 rotating clockwise may tend to rotate the body of the aircraft 100 counterclockwise. To counteract this torque effect, the left prop rotor 136l may be tilted slightly forward of vertical and the right prop rotor 136r may be tilted slightly aft of vertical, such that the prop rotors 136l, 136r exert a clockwise torque (e.g., yawing moment) on the body of the aircraft 100 that counteracts the torque effects of the rotating central rotor 140. In some embodiments, the yawing moment can be created by varying the speed of the prop rotors 136l, 136r. For example, rotating the prop rotor 136l faster than the prop rotor 136r creates a yawing moment to the right, and rotating the prop rotor 136r faster than the prop rotor 136l creates a yawing moment to the left.These methods of generating a yawing moment can be utilized to rotate and / or to counter the torque generated when the main rotor is powered.

[0060] Differential control of the prop rotors 136l, 136r may further be used to steer the aircraft 100 during vertical flight, such as takeoff, landing, hovering, lateral movements, and / or slow forward or reverse flight. As described above, differential tilt of the prop rotors 136l, 136r may be used to generate a yawing moment for maneuverability about a vertical axis. Differential rotational speeds of the prop rotors 136l, 136r may be used to generate a rolling moment for maneuverability about a longitudinal axis. For example, powering the left prop rotor 136l at a higher rotational speed relative to the right prop rotor 136r creates a right or clockwise rolling moment, and powering the right prop rotor 136r at a higher rotational speed relative to the left prop rotor 136l creates a left or counterclockwise rolling moment. Simultaneously pitching the propeller rotors 136l, 136r forward or aft from the vertical and / or pitching the center rotor 140 forward or aft creates a pitching moment for maneuverability about a lateral axis. Rolling or pitching the aircraft 100 from a vertical attitude creates a horizontal component of lift that can be utilized for forward, aft, and / or lateral movement, typically during vertical flight.

[0061] Horizontal or forward flight, including straight and level flight, climbing, descending, turning, etc., can be achieved with the prop rotors 136l, 136r in a forward flight position such that the axis of rotation of each prop rotor 136l, 136r is within about 30 degrees of the horizon. In the forward flight position, the rotating prop rotors 136l, 136r generate primarily forward thrust substantially parallel to the direction of flight. During forward flight, the central rotor 140 is unpowered and can rotate on its own axis. Preferably, the central rotor 140 is tilted upward (e.g., between about 1 degree and 20 degrees or more, with the high side of the central rotor 140 pointed in the direction of flight). In some embodiments, the central rotor 140 is tilted at an angle of about 1 degree to 20 degrees in forward flight. Thus, in forward flight, the aircraft 100 effectively functions as a gyroplane, with the powered propeller rotors 136l, 136r generating thrust and the spinning central rotor 140 providing lift. The tail section 150 provides directional stability during forward flight.

[0062] In various embodiments, the tail section 150 may or may not include control surfaces. For example, the horizontal stabilizer 152 may include one or more elevators configured to provide pitch control, and the vertical stabilizers 154 may include rudders each configured to provide yaw control. In some embodiments, the tail section 150 includes only rudders or only elevators, and in other embodiments, the tail section 150 includes neither rudders nor elevators. Instead, any or all of the pitch, yaw, and roll may be controlled by variable tilt-pitch prop rotors. Pitch and / or roll may also be controlled at least in part by the tilt of the central rotor 140.

[0063] Pitch control in forward flight can be achieved by tilting the central rotor 140 forward or aft. Pitch control in forward flight can also be achieved by simultaneously tilting both prop rotors 136l, 136r higher or lower relative to the longitudinal or x-axis. For example, simultaneous upward tilt of the prop rotors 136l, 136r can generate a nose-up pitching moment, and simultaneous downward tilt of the prop rotors 136l, 136r can generate a nose-down forward pitching moment.

[0064] Roll control in forward flight can be achieved by tilting the central rotor 140 left or right. However, controlling roll by tilting the central rotor 140 requires a lateral tilt mechanism for the central rotor 140. In some embodiments, the lower rotor hub 300 and / or upper rotor hub assembly 400 may be simplified by providing only forward-backward tilt, rather than lateral tilt. In such an embodiment, aircraft roll can be achieved based on differential tilt of the prop rotors 136l, 136r. For example, tilting the left prop rotor 136l slightly upward relative to the horizon and / or tilting the right prop rotor 136r slightly downward relative to the horizon creates a right or clockwise rolling moment. Tilting the right prop rotor 136r slightly upward relative to the horizon and / or tilting the left prop rotor 136l slightly downward relative to the horizon creates a left or counterclockwise rolling moment.

[0065] Yaw control in forward flight can be achieved by providing differential power to the left and right prop rotors 136l, 136r. For example, varying the relative speed of the prop rotors 136l, 136r such that the left prop rotor 136l rotates at a higher rotational speed than the right prop rotor 136r creates a right yawing moment. Varying the relative speed of the prop rotors 136l, 136r such that the right prop rotor 136r rotates at a higher rotational speed than the left prop rotor 136l creates a left yawing moment.

[0066] In various embodiments, turns in forward flight may be accomplished by yaw control (e.g., by variable relative prop rotor speed), by roll control alone (e.g., by variable relative pitch of the prop rotors), or by a combination of yaw and roll control. In some embodiments, turns with a combination of yaw and roll control may be desirable to maintain coordinated flight without skidding during turns. For example, a right turn may be performed by simultaneously (or substantially simultaneously) pitching the left prop rotor 136l upward, increasing the rotational speed of the left prop rotor 136l, pitching the right prop rotor 136r downward, and / or decreasing the rotational speed of the right prop rotor 136r.

[0067] In addition to the vertical and forward flight modes, the aircraft 100 can further transition between forward and vertical flight modes during flight. Maneuvers for transitioning from vertical flight to forward flight, and from forward flight to vertical flight, are described below. Advantageously, the aircraft of the present disclosure can seamlessly transition between flight modes without sacrificing stability or controllability during the transition.

[0068] The aircraft 100 may transition from vertical to forward flight at various times during a mission, for example, after vertical takeoff when entering the cruise portion of the flight to the remote location, after a period of hovering at the remote location, etc. The transition from vertical to forward flight begins with the aircraft 100 configured for vertical flight. In this configuration, the propellers 136l, 136r are in the VTOL / hovering position shown in FIG. 6, and the central rotor 140 may rotate under power while substantially parallel to the propellers 136l, 136r. To transition to forward flight, the propellers 136l, 136r are simultaneously tilted forward to the forward flight position shown in FIG. 6. At approximately the same time, the central rotor 140 is tilted aft (e.g., higher toward the front of the aircraft and lower toward the rear of the aircraft). If the middle rotor 140 was powered during the preceding vertical or hovering flight, the rotor motors may continue to spin the middle rotor 140 until the aircraft is established in forward flight. If the middle rotor 140 was not powered during the preceding vertical or hovering flight, the rotor motors may be activated during the transition to spin the middle rotor 140 to an appropriate rotational speed to provide lift for forward flight. Once the aircraft 100 is established in forward flight, the rotor motors may be deactivated because the airflow relative to the middle rotor 140 is fast enough to cause the middle rotor 140 to spin on its axis.

[0069] The aircraft 100 may transition from forward flight to vertical flight at various times during a mission, for example, when the aircraft 100 arrives at a remote location where it hovers for a period of time, when it arrives at a landing site, etc. The transition from forward flight to vertical flight begins with the aircraft 100 configured for horizontal flight. In this configuration, the propellers 136l, 136r are in the forward flight position shown in FIG. 6, and the central rotor 140 is rotating by free autorotation as the aircraft travels in forward flight. To transition to vertical flight, the propellers 136l, 136r are simultaneously tilted upward to the VTOL / hover position shown in FIG. 6. The central rotor 140 is tilted forward (e.g., to a horizontal position substantially parallel to the propellers 136l, 136r). In some embodiments, the propeller rotors 136l, 136r may be tilted beyond vertical, for example, between 5 degrees and 30 degrees behind vertical, when it is desired to slow the forward airspeed of the aircraft 100. As the airspeed decreases and / or as the middle rotor 140 tilts back to a horizontal attitude, the rotation of the middle rotor 140 may be reduced and / or stopped. The rotor motors may be activated to spin the middle rotor 140 to provide additional lift and / or stabilization to the aircraft 100 during the vertical flight phase.

[0070] Throughout the foregoing disclosure, the proprotors 136l, 136r have been described as independently tiltable and controllable to achieve various flight control functions. FIGS. 7-10 further illustrate example components configured to implement the proprotor control functions described herein. FIG. 7 illustrates an intermediate portion of the lateral boom 132 of an example aircraft 100, including a proprotor support and control components disposed thereon. FIG. 8 is a detailed view of the proprotor support and control components of FIG. 7. As illustrated in FIG. 7, in some embodiments, the boom 132 can include a tubular intermediate structure, and the distal arms 134l, 134r can be narrower tubular components partially coaxially mounted within the tubular intermediate structure. As illustrated in FIGS. 7 and 8, the aircraft 100 includes a gearbox 200, which can be disposed within the proprotor tilt control housing 130 illustrated in FIGS. 1-4. 8, the gearbox 200 includes a master gear 204 that is independently driven by a prop rotor tilt servo 202. The master gear 204 is arranged to mesh with a slave gear 206 that is coaxially fixed to the inner ends of the distal arms 134l, 134r. Thus, the tilt servo 202 can tilt the prop rotors 136l, 136r by rotating the master gear 202.

[0071] As shown in Figures 9 and 10, a prop rotor motor 210 is disposed at the outer end of each distal arm 134l, 134r of the boom 132. Each prop rotor motor 210 is rotationally fixed relative to the corresponding distal arm 134l, 134r such that the axis of rotation of the prop rotor motor 210 is perpendicular to the lateral axis along the distal arm 134l, 134r. Thus, under the control of the prop rotor tilt servo 202, rotation of the distal arm 134l, 134r about the lateral axis produces a fore-aft tilt of the axis of rotation of the prop rotor motor 210. Thus, each of the above tilt operations for the prop rotors 136l, 136r can be achieved by actuating the prop rotor tilt servos 202 individually or simultaneously.

[0072] 11-15 illustrate an exemplary lower rotor hub 300 for an exemplary aircraft, such as aircraft 100. As described above, the lower rotor hub 300 serves as the attachment point for the upper rotor hub assembly 400 and the central rotor 140. As will now be described, the lower rotor hub 300 is also configured to provide tilt and powered rotation of the central rotor 140. The lower rotor hub 300 includes a rotor mount shaft 302 having one or more mounting pin holes 303 extending therethrough, a central rotor slave gear 304 meshed with a central rotor master gear 306, a central rotor drive motor 308, a tilt bearing 310, and a central rotor tilt servo 312.

[0073] The rotor mount shaft 302 serves as a mounting point for the central rotor 140. The central rotor 140, not shown in Figures 11-15, can be mounted to the aircraft 100 by coupling an upper rotor hub assembly 400 to the rotor mount shaft 302 and securing the upper rotor hub assembly 400 using one or more pins that extend through mounting pin holes 303. The pin-based mounting of the upper rotor hub assembly 400 allows the central rotor 140 to be easily and quickly mounted and removed from the aircraft 100 for transport.

[0074] The central rotor slave gear 304 is coaxial with the rotor mount shaft 302 and is configured to transmit the rotational motion of the central rotor master gear 306 to the rotor mount shaft 302 to drive the central rotor 140 during powered operation of the central rotor 140. In some embodiments, the central rotor slave gear 304 is such that the rotational motion of the central rotor slave gear is coupled to the rotor mount shaft 302 by a clutch mechanism and / or a one-way bearing (e.g., one-way bearing 305) such that the rotational motion of the central rotor slave gear 304 in a first direction (e.g., clockwise) is transmitted to the rotor mount shaft 302, but the rotor mount shaft 302 is free to rotate in the same direction (e.g., clockwise) when the central rotor slave gear 304 is not rotating or is rotating slower than the rotor mount shaft 302. Thus, the central rotor drive motor 308 can power the central rotor 140 by rotating the central rotor master gear 306 (e.g., during vertical flight and / or during the transition from vertical to forward flight), which in turn rotates the central rotor slave gear 304 and the rotor mount shaft 302.

[0075] The central rotor tilt servo 312 is configured to tilt the lower rotor hub 300 relative to the mast 120. Actuation of the central rotor tilt servo 312 causes rotation of the lower rotor hub 300 about the tilt bearing 310, which corresponds to movement about a lateral axis perpendicular to the rotor mount shaft 302.

[0076] Figure 14 illustrates an exemplary forward-most tilted position of the lower rotor hub 300. In the tilted position illustrated in Figure 14, the rotor mount shaft 302 is substantially aligned with the vertical axis of the aircraft 100, and the spinning central rotor 140 attached to the lower rotor mount 300 generates lift directly above. The tilted position illustrated in Figure 14 may be used, for example, during vertical flight while the prop rotors 136l, 136r are in the VTOL / hover position illustrated in Figure 6.

[0077] FIG. 15 illustrates an example of the rearmost tilt position of the lower rotor hub 300. In the tilt position illustrated in FIG. 15, the rotor mount shaft 302 is tilted rearward at approximately 20 degrees relative to the vertical, so that the rotating central rotor 140 attached to the lower rotor mount 300 rotates in a plane tilted at approximately 20 degrees relative to the longitudinal axis of the aircraft 100. The tilt position illustrated in FIG. 15 may be used, for example, during horizontal flight while the propeller rotors 136l, 136r are in the forward flight position illustrated in FIG. 6. The central rotor tilt servo 312 tilts the lower rotor hub 300 between the positions illustrated in FIG. 14 and FIG. 15 as the aircraft 100 transitions from vertical to forward flight or from forward to vertical flight, as described above.

[0078] 16-20 illustrate an exemplary upper rotor hub assembly, such as an upper rotor hub assembly 400 of the aircraft 100. FIG. 16 illustrates the upper rotor hub assembly 400 including two attachment members 402, 404 coupleable to the lower rotor hub 300 of FIGS. 11-15, as well as the inner portions of the rotor blades 142 of the central rotor 140. FIGs. 17 and 18 illustrate the attachment members 402, 404 separately, including an exemplary rotor blade 142 attached to the first attachment member 402. FIGs. 19 and 20 illustrate the upper rotor hub assembly 400 in a folded configuration.

[0079] As noted above, the central rotor 140 of the aircraft 100 functions similarly to a gyroplane rotor when the aircraft 100 is in a forward flight mode. In contrast to helicopter rotors, where the blades are hinged or otherwise allowed to move vertically and / or horizontally relative to the main rotor hub, gyroplane rotors operate most efficiently when the blades are rigidly fixed relative to the central hub, with each opposing blade remaining symmetrically opposed. Although not required, precise alignment of the blades can greatly improve performance. Thus, if compact transportation of the aircraft 100 is desired, it may be tedious to remove the blades 142 from the upper rotor hub assembly 400 for transportation, due to the time required to carefully align the blades 142 when reattaching them. As will be described, the upper rotor hub assembly 400 can be easily removed from and attached to the lower rotor hub 300, and the central rotor 140 and the entire upper rotor hub assembly 400 can be folded up for transportation in a compact form, while the blades 142 remain attached to the mounting members 402, 404.

[0080] The upper rotor hub assembly 400 includes a first mounting member 402 and a second mounting member 404. The mounting members 402, 404 each include a mounting pin hole 405 configured to align with the mounting pin hole 303 of the lower rotor hub 300 of FIGS. 11-15. As shown in FIG. 16, the mounting members 402, 404 are shaped to nest together when both mounting members 402, 404 are mounted on the lower rotor hub 300. The mounting members 402, 404 are also shaped such that when nested together in the mounted configuration, each mounting member 402, 404 can independently teeter about the axis of its mounting pin. In some embodiments, the aircraft 100 can operate with only two blades 142 by using only the first mounting member 402 or only the second mounting member 404. Two-blade operation is associated with less lift and less induced drag during forward flight and may be desirable when the aircraft 100 is carrying a relatively light load and less lift capacity is required. Four-blade operation is associated with more lift and more induced drag during forward flight and may be desirable when the aircraft 100 is carrying a relatively heavy load and more lift capacity is required.

[0081] Each mounting member 402, 404 includes two mounting brackets 406 disposed on opposite sides of the mounting members 402, 404 about the center of the hub. Each mounting bracket 406 includes two or more mounting holes 408 spaced to align with corresponding mounting holes 409 in the rotor blades 142. In some embodiments, more than two mounting holes 408, 409, such as three or more mounting holes, are provided to form a structurally robust connection between the rotor blades 142 and the mounting brackets 406.

[0082] The mounting members 402, 404 each include two hinges 410 disposed between a mounting bracket 406 and a central portion of the mounting members 402, 404. The hinges 410 allow the mounting brackets 406 and the rotor blades 142 to fold about the axis of the hinges 410 while the aircraft is not flying. Each mounting bracket 406 is rigidly coupled to a locking plate 414 having holes disposed to align with locking pin holes 413 in the central portion of the mounting members 402, 404. When the hinges 410 are in a fully extended position (e.g., for flight), the hinges 410 may be locked in the fully extended position by inserting a locking pin 412 through the locking pin hole 413 and the adjacent locking plate 414. The locking pins 412 may include a retention mechanism, such as a spring-loaded retention ball, to prevent the locking pins 412 from being pulled out during operation.

[0083] In some embodiments, instead of or in addition to being foldable, the mounting members 402, 404 may also allow the rotor blades 142 to be removed from the mounting members 402, 404 in a manner that maintains alignment of the rotor blades 142 when the rotor blades 142 are reinserted. For example, the rotor blades 142 may be slidably mounted along one or more rails disposed within the mounting brackets 406. Each mounting bracket 406 may include a release button that, when depressed, allows the rotor blades 142 within the mounting brackets 406 to slide outward and be removed. In some embodiments, the mounting brackets 406 and / or the mounting members 402, 404 may include a bayonet-type mounting system that maintains proper alignment between opposing rotor blades 142. Bayonet-type mounting systems are described in more detail with reference to FIGS. 25 and 26.

[0084] 19 and 20 show the folded configuration of the mounting members 402, 404. As shown in FIG. 19 and 20, removal of the locking pin 412 from the mounting members 402, 404 allows the locking plate 414 to move away from the locking pin hole 413, allowing the mounting members 402, 404 to fold into a folded configuration at the hinge 410. In the folded configuration, both the mounting bracket 406 and the rotor blades 142 attached to each mounting member 402, 404 are substantially parallel. Thus, a two-bladed or four-bladed central rotor 140 can be transported in a relatively narrow rectangular container having a length slightly longer than each of the rotor blades 142. This folded configuration is substantially more efficient than transporting the central rotor 140 in a flying configuration, which requires a container having two vertical dimensions at least twice the length of each rotor blade 142. Additionally, in some cases, it may be desirable to fold the central rotor 140 while it remains attached to the aircraft 100. The folding mechanisms described herein allow two or four rotor blades 142 to fold upwardly, thereby minimizing the horizontal footprint of the aircraft 100 while it is stored on the ground.

[0085] Figures 21 and 22 show the upper rotor hub assembly 400 of Figures 16-20 coupled to the lower rotor hub 300 of Figures 11-15. Each mounting member 402, 404 is coupled to the lower rotor hub 300 by a mounting pin 416 that passes through a mounting pin hole 405 in the mounting member 402, 404 and a mounting pin hole 303 in the lower rotor hub 303. As well as a locking pin 412 that locks the mounting members 402, 404 in a fully extended position, the mounting pin 416 may include a retention mechanism, such as a spring-loaded retention ball or the like, to prevent the mounting pin 416 from being pulled out during operation.

[0086] 23 and 24 show further exemplary configurations of the upper rotor hub assembly 400. The exemplary upper rotor hub assembly 400 of FIGS. 23 and 24 further includes an upper rotor hub 416 that serves as a removable attachment point for the mounting members 402, 404. The mounting members 402, 404 may be coupled to the upper rotor hub 416 by similar mounting pins 412 or the like. In some embodiments, the mounting pins 412 coupling the mounting members 402, 404 to the upper rotor hub 416 may be permanent or semi-permanent pins rather than the easily removable pins of FIGS. 16-22.

[0087] 24, the upper rotor hub 416 can then be connected to the rotor mount shaft 302 of the lower rotor hub by an additional mounting pin 418, which may also include a spring-based or other retention element configured to be quickly releasable. Thus, the entire upper rotor mount hub assembly 400 can be folded and subsequently removed from the aircraft by removing the single mounting pin 418.

[0088] 25 and 26 show a further exemplary configuration of the upper rotor hub assembly 400 in which a bayonet-type mounting system allows rotor blades 142 to be attached to and removed from the upper rotor hub assembly 400. Similar to the configuration of FIGS. 23 and 24, the upper rotor hub assembly 400 of FIGS. 25 and 26 includes two mounting members 402, 404 attached to an upper rotor hub 416. Each rotor blade 142 is attached to a mounting bracket 406 by two, three, or more fasteners. Each mounting bracket 406 is secured to a mounting body 420, some or all of which may be integrally formed with the mounting bracket 406. Blade mounting pin holes 422 extend laterally through the mounting body 420.

[0089] Each opposite end of each mounting member 402, 404 includes a mounting body opening 424 sized and shaped to receive a mounting body 420. An additional blade mounting pin hole 426 extends laterally through the side of the mounting member 402, 404. Thus, as shown by the transition from FIG. 25 to FIG. 26, each rotor blade 142 can be mounted by sliding the mounting body 420 into the mounting body opening 424 until the blade mounting pin hole 422 is substantially aligned with the blade mounting pin hole 426. The blade mounting pin 428 can then be inserted into the blade mounting pin holes 422, 426 to secure the rotor blade 142 to the upper rotor hub assembly 400. Removal of the blade, for example for storage, transportation, etc., can be accomplished by removing the blade mounting pin 428 from the blade mounting pin holes 422, 426, followed by sliding the mounting body 420 out of the mounting body opening 424.

[0090] As noted above, when operating in vertical powered flight, such as in the hovering or VTOL flight phases, it is typically desirable for the rotor to have a positive blade pitch. In contrast, when autorotation is used, such as in the forward flight of a gyroplane, it is desirable for the rotor blades to have a flat or zero pitch, or a positive pitch that is substantially less than in vertical flight. Accordingly, some embodiments of the present technology include a rotor assembly configured to selectively vary the pitch angle of the rotor blades while maintaining a teetering motion that is desirable for low pitch forward flight. Advantageously, the embodiments disclosed herein achieve blade pitch control without the weight and complexity of a swashplate as typically utilized for blade pitch control in helicopters.

[0091] FIG. 27 illustrates an exemplary embodiment of a rotor hub assembly including a teetering pivot point and a synchronizing linkage for controlling the pitch of the rotor blades. FIGs. 28 and 29 illustrate a side view and a cross-sectional view of the rotor hub assembly of FIG. 27 in a zero pitch configuration. FIGs. 30 and 31 illustrate a side view and a cross-sectional view of the rotor hub assembly of FIGs. 27-29 in a positive pitch configuration. FIG. 32 illustrates an exploded view of the rotor hub assembly of FIGs. 27-31. The rotor assemblies illustrated in FIGs. 27-32 may be implemented in combination with any of the aircraft disclosed herein.

[0092] For a gyrocopter rotor assembly to generate upward thrust, the pitch of the blades is increased from zero or near zero to a selected pitch angle greater than zero, and the rotor is rotated at an RPM that generates sufficient thrust to lift the weight of the aircraft and its payload. Figures 28 and 29 show the assembly with the rotor blades at 0 degrees pitch, while Figures 30 and 31 show the assembly with the rotor blades at a higher pitch that creates lift.

[0093] As shown in Figures 28, 30, and 32, the rotor head assembly includes a teetering pivot point attached to the rotating shaft so that the rotor head can teeter freely during forward flight. The rotor head assembly further includes a synchronizing linkage that connects two opposing arms of the rotor head that hold the two rotor blades. These linkages synchronize the movement of the two arms as they slide and twist to produce the desired pitch.

[0094] Each arm of the rotor assembly includes an outer cylinder configured to hold a removable rotor blade, as described in more detail with reference to Figures 25 and 26, and an inner cylinder sized and shaped to fit at least partially within the outer cylinder. A biasing element, such as a gas spring, is disposed between an end backstop of the inner cylinder and an inwardly facing surface of the outer cylinder arm. The outer cylinder arms are connected at both ends to a synchronizing linkage via arms 1 and 2 that extend through arm openings on the outer surface of the outer cylinder. Each arm passes through two arm openings on the corresponding outer cylinder and two rotor orientation tracks on the corresponding inner cylinder, and is coupled at both ends to the outer ends of the synchronizing linkage.

[0095] Advantageously, the rotor assembly mechanism of FIGS. 27-32 can provide automatic adjustment of blade pitch based on the rotational speed of the rotor assembly without requiring a servo or other control mechanism to adjust the blade pitch. For example, the gas springs and associated components can automatically increase blade pitch at higher RPMs and automatically decrease blade pitch at lower RPMs. The gas springs are rated to collapse at a specific poundage of force. Thus, as the rotor rotational speed increases in powered vertical flight mode, the corresponding increase in centrifugal force causes the gas springs to at least partially collapse and the outer cylinders to slide outward. As the outer cylinders slide outward, the tilt of the rotor orientation track causes the outer cylinders and attached rotor blades to twist to generate the desired pitch for the blades. The synchronizing linkages simultaneously slide outward and twist to the desired pitch to generate lift, maintaining equal or substantially equal blade pitch between the two blades. As the RPM subsequently drops, the outer cylinder slides inward with the help of two gas springs, causing the blade angle to return to zero as arms 1 and 2 slide within the rotor's orientation track, allowing the gyrocopter to fly forward with the help of the pusher motor / propeller assembly.

[0096] In some embodiments, the gas springs may be configured to collapse when a predetermined outward force (e.g., radially outward from the center of the rotor assembly toward the blades) is applied. The predetermined force may be selected based at least in part on the mass of the outer cylinder and blades such that the outer cylinder collapses and increases rotor blade pitch at a predetermined rotational speed range. In one particular example, the predetermined force is selected such that a lower RPM range, such as 250-450 RPM, does not generate enough centrifugal force to cause the gas springs to collapse outward, while a higher RPM range, such as above 550 RPM, generates enough centrifugal force to keep the gas springs collapsed. Thus, the aircraft may be controlled to operate with the main rotors rotating at or below 450 RPM during horizontal flight and rotating at or above 550 RPM during vertical or hovering flight. In some embodiments, the aircraft may be configured to avoid operating for extended periods with the main rotor spinning at speeds in an intermediate or safe RPM range (e.g., between 450 RPM and 550 RPM in the specific example above), where the centrifugal forces generated by the rotor blades and outer cylinder may be great enough to partially collapse the gas springs, but not enough to completely collapse the gas springs.

[0097] It may be desirable to increase or decrease the rotational speed of the rotor on command, consistent with automatic control of blade pitch based on rotor RPM. It may also be desirable to increase or decrease rotor RPM in flight to achieve desired or optimized flight characteristics. FIG. 33 illustrates an exemplary gearing system for increasing the RPM of the upper rotor hub assembly of FIGS. 27-32. FIG. 34 illustrates a cross-sectional view of a braking system for reducing the rotational speed of the upper rotor hub assembly of FIGS. 27-32.

[0098] As shown in FIG. 33, the rotational speed of the rotor can be increased by a motor through a large gear with a one-way bearing, as described elsewhere herein. When that motor is powered and the rotor head and the blades attached to it rotate, a large torque is generated that, if not countered, will cause the aircraft to spin uncontrollably. To avoid undesirable rotation, two prop rotors located on either side of the aircraft at a particular CG (center of gravity) location (e.g., as shown in FIGS. 1-4) can be operated independently at different speeds to counteract the torque generated by the rotor head assembly. The rotational speed of the prop rotors is variable to match the counter torque force required based on the torque generated by the rotor head assembly. In some embodiments, depending on the amount of torque generated by the rotor head assembly, one prop rotor (e.g., the left prop rotor) can operate at full speed and the other prop rotor can operate at a lower RPM or completely stopped to fully counter the torque of the rotor head assembly. In some embodiments, the other prop rotor (e.g., the right prop rotor) can be rotated 180 degrees and operated at an appropriate RPM to provide further counter torque. Once the aircraft transitions to forward flight, the prop rotor can be transitioned to rotate at the same RPM to provide stability and control during the level flight phase.

[0099] Now referring to FIG. 34, a disc brake is located on the bottom of the rotor shaft to slow or control the rotor RPM. The disc brake is part of the pivot assembly bracket and is coupled with a bracket that holds the brake pads, calipers, and brake servo. The calipers that hold the brake pads are actuated by the brake servo and can be actuated at any time to slow the rotor down or assist in bringing the rotor to a complete stop after the aircraft has safely landed. This bracket assembly allows the rotor head to move forward or backward as needed for the desired flight mode.

[0100] 35-37 show an exemplary aircraft including a tiltable tail. In some embodiments, the tail, including a horizontal stabilizer and one or two rudders, rotates downwards 90 degrees during vertical flight, thereby streamlining the airflow generated by the downward thrust from the rotating blades of the main rotor. The tail can be rotatable about the longitudinal axis of the horizontal stabilizer (e.g., a transverse axis with respect to the aircraft). FIGS. 35 and 36 show the tail in an upright position, such as for forward flight. FIG. 37 shows the tail in a lowered position, tilted approximately 90 degrees forward or backward, such that the horizontal stabilizer is oriented substantially in a vertical plane. When the tail assembly is in the lowered position, it has two additional functions: First, it moves the gyrocopter forward or backward in a controlled manner by changing the angle of the tail from ±90 degrees. Second, the rudders allow for additional counter torque fine adjustments, allowing the aircraft to turn left or right. The downward-facing wings have the same function, but with a primary counter torque function. Additionally, the vertical attitude of the horizontal stabilizer in the lowered position reduces interference with the downward airflow generated by the rotors, improving the efficiency of vertical and hovering flight. Rotation of the tiltable tail between the upright and lowered positions can be actuated by a tail tilt servo located within the aircraft.

[0101] 38-41 illustrate a further exemplary embodiment of an aircraft including a single prop-rotor and pivotable wings configured to operate as a control surface. The aircraft of FIGS. 38-41 includes a central rotor and a single prop-rotor mounted on a mast to provide centerline thrust to the aircraft. The independently pivotable wings are mounted to the sides of the mast. It will be understood that the single prop-rotor configuration of FIGS. 38-41 can be implemented with any of the aircraft embodiments disclosed herein.

[0102] As shown in Figures 38 and 39, in horizontal forward flight, the two wings have substantially the same horizontal attitude so that the wings are streamlined for forward flight. In some embodiments, the wings may be further used for flight control functions in forward flight, such as to provide rolling or pitching moments.

[0103] As shown in Figures 40 and 41, the two wings can be differentially positioned to provide a counter torque moment while the main rotor is powered in the vertical or hovering flight phase. In this counter torque position, the left wing pivots more than 90 degrees and the right wing pivots less than 90 degrees, so that the left wing deflects the rotor downwash forward and the right wing deflects the rotor downwash aft. Thus, the counter torque configuration of Figures 40 and 41 creates a counter clockwise torque that opposes the clockwise torque created by the powered rotor.

[0104] Although specific embodiments have been described, these embodiments are presented as examples only and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in other various forms. Furthermore, various omissions, substitutions, and modifications of the systems and methods described herein may be made without departing from the spirit of the disclosure. The appended claims and their equivalents are intended to cover such forms or modifications as fall within the scope and spirit of the disclosure. Thus, the scope of the disclosure is defined solely by reference to the appended claims.

[0105] It should be understood that configurations, materials, properties, or groups described in connection with a particular aspect, embodiment, or example are applicable to other aspects, embodiments, or examples described in this section or elsewhere in this specification, unless a contradiction occurs. All configurations disclosed in this specification (including the accompanying claims, abstract, and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such configurations and / or steps are mutually exclusive. Protection is not limited to the details of the foregoing embodiments. Protection extends to any novel one or any novel combination of configurations disclosed in this specification (including the accompanying claims, abstract, and drawings), or any novel one or any novel combination of steps of any method or process so disclosed.

[0106] Furthermore, certain configurations described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various configurations described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Furthermore, although configurations may be described above as acting in a particular combination, one or more configurations from a claimed combination can, in some cases, be carved out of the combination, and the combination can be claimed as a subcombination or a variation of the subcombination.

[0107] Furthermore, although operations may be depicted in the figures or specification in a particular order, such operations need not be performed in the particular order or sequential order shown, or all of the operations need not be performed, to achieve desirable results. Other operations not shown or described may be incorporated into the exemplary methods and processes. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the described operations. Furthermore, in other implementations, operations may be rearranged or reordered. Those skilled in the art will appreciate that in some embodiments, the actual steps performed in the illustrated and / or disclosed processes may differ from those shown in the figures. Depending on the embodiment, certain steps described above may be eliminated and other steps may be added. Furthermore, the configurations and attributes of certain embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Also, the separation of various system components in the above implementations should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems may generally be integrated together in a single product or packaged in multiple products.

[0108] For the purpose of this disclosure, certain aspects, advantages, and novel configurations are described herein. Not all such advantages may be achieved according to a particular embodiment. Thus, for example, a person skilled in the art will recognize that the present disclosure may be embodied or implemented to achieve one advantage or a group of advantages as taught herein, without necessarily achieving other advantages as may be taught or suggested herein.

[0109] Conditional language such as "can," "could," "might," "may," and the like, unless otherwise specified or understood otherwise within the context in which it is used, is generally intended to convey that certain embodiments include certain configurations, elements, and / or steps, but not other embodiments. Thus, such conditional language is not generally intended to imply that the configurations, elements, and / or steps are somehow required in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether those configurations, elements, and / or steps are included in or performed in a particular embodiment, with or without user input or prompting.

[0110] Conjunctive language, such as the phrase "at least one of X, Y, and Z," is understood in the context as it is commonly used, unless otherwise noted, to convey that an item, term, etc., can be either X, Y, or Z. Thus, such conjunctive language is generally not intended to imply that a particular embodiment requires the presence of at least one of X, at least one of Y, and at least one of Z.

[0111] The scope of the present disclosure is not intended to be limited by the specific disclosure of preferred embodiments in this section or elsewhere herein, but may be defined by the claims as presented in this section or elsewhere herein, or as presented in the future. The language of the claims should be interpreted broadly based on the language used in the claims, and not limited to the examples described herein or during the examination of the application, which examples should be interpreted as non-exclusive.

Claims

1. a propeller configured to provide forward thrust; and a rotor assembly, The rotor assembly includes: a plurality of rotor blades configured to provide lift; and at least one mounting member; Each of the mounting members is The central section, a blade pitch adjustment linkage coupling two of the plurality of rotor blades to opposing ends of the central section, the blade pitch adjustment linkage configured to maintain the two rotor blades at a first blade pitch while a rotational speed of the rotor blades is less than a first rotational speed threshold and to maintain the two rotor blades at a second blade pitch while a rotational speed of the rotor blades is greater than a second rotational speed threshold, the second rotational speed threshold being greater than the first rotational speed threshold; the blade pitch adjustment linkages each include a gas spring coupling one of the rotor blades to the center section, the gas springs configured to cause an increase in the blade pitch when subjected to an increase in centrifugal force associated with an increase in rotational speed of the rotor blades.

2. 2. The aircraft of claim 1, wherein the gas spring is configured to remain in an extended position over a range of rotational speeds below the first rotational speed threshold.

3. 3. The aircraft of claim 2, wherein the gas spring is further configured to collapse from the extended position to a fully collapsed position when a rotational speed of the rotor blade increases from the first rotational speed threshold to the second rotational speed threshold.

4. 2. The aircraft of claim 1, wherein the first rotational speed threshold is less than or equal to 450 RPM and the second rotational speed threshold is at least 550 RPM.

5. 2. The aircraft of claim 1, wherein the second blade pitch is a positive blade pitch and the first blade pitch is a flat blade pitch or a less positive blade pitch than the second blade pitch.

6. The aircraft of claim 1 , further comprising a control circuit configured to rotate the rotor blades via a motor.

7. 7. The aircraft of claim 6, wherein the control circuitry is configured to rotate the rotor blades at a rotational speed greater than the second rotational speed threshold while the aircraft is operating in a vertical flight mode or a hovering flight mode.

8. 7. The aircraft of claim 6, wherein the control circuitry is configured to rotate the rotor blades at a rotational speed slower than the first rotational speed threshold while the aircraft is operating in a forward flight mode in which the one or more propeller rotors provide forward thrust and the rotor assembly is free to rotate.

9. 7. The aircraft of claim 6, wherein the control circuitry is configured to prevent sustained rotation of the rotor blades within an intermediate range of rotational speeds between the first rotational speed threshold and the second rotational speed threshold.

10. 7. The aircraft of claim 6, wherein the motor is coupled to the rotor assembly by a clutch mechanism or a one-way bearing that rotatably couples the motor to the rotor assembly when the motor is providing power and allows the rotor assembly to rotate freely when the motor is not providing power.

11. the control circuit switches the motor from a vertical flight mode or a hovering flight mode in which the motor rotates the rotor blades at a rotational speed greater than the second rotational speed threshold; at least one of said propeller rotors is actuated to provide forward thrust; while the rotational speed of the rotor blades is in an intermediate range between the first rotational speed threshold and the second rotational speed threshold, causing the motor to stop rotating the rotor blades such that the rotational speed of the rotor blades drops below the first rotational speed threshold and the blade pitch adjustment linkage moves the two rotor blades from the second blade pitch to the first blade pitch; The aircraft of claim 6 , configured to transition to a forward flight mode.

12. 12. The aircraft of claim 11, wherein the control circuitry is further configured to tilt the rotor assembly from a vertical position to a rearward tilted position that facilitates free rotation of the rotor blades in the forward flight mode.

13. from a forward flight mode in which the one or more propeller rotors provide forward thrust and the rotor blades are free-rotating at a rotational speed less than the first rotational speed threshold; shutting down at least one or more of the propeller rotors to cease providing forward thrust; while the rotational speed of the rotor blades is in an intermediate range between the first rotational speed threshold and the second rotational speed threshold, actuating the motor such that the blade pitch adjustment linkage moves the two rotor blades from the first blade pitch to the second blade pitch to increase the rotational speed of the rotor blades above the second rotational speed threshold; The aircraft of claim 6 , configured to transition to a vertical flight mode or a hovering flight mode.

14. 14. The aircraft of claim 13, wherein the control circuitry is further configured to tilt the rotor assembly from a tilted aft position to a vertical position when transitioning to the vertical flight mode or the hovering flight mode.

15. 2. The aircraft of claim 1, wherein the blade pitch adjustment linkage comprises at least one synchronizing linkage coupled to the mounting member and configured to synchronize blade pitch of the rotor blades.

16. 16. The aircraft of claim 15, wherein the rotor assembly further includes inner cylinders extending from opposite ends of the center section, each of the two rotor blades being coupled to an outer cylinder that slidingly receives one of the inner cylinders.

17. 17. The aircraft of claim 16, wherein the outer cylinder includes a pin receiving opening, the inner cylinder includes an opening defining a track, and the blade pitch adjustment linkage includes a pin extending through an opening in the inner cylinder, the pin sliding through the track as the outer cylinder slides relative to the inner cylinder, thereby causing relative rotation of the outer cylinder with respect to the inner cylinder.

18. 2. The aircraft of claim 1, wherein the aircraft includes at least four rotor blades and at least two mounting members, each mounting member coupled to two oppositely disposed rotor blades of the plurality of rotor blades, and each mounting member shaped to enable independent teetering of at least one other mounting member.

Images