Short-distance take-off and landing carrier with forward swept wings

Abstract

A short take-off and landing (STOL) vehicle includes a tail having a surface and a fuselage having a surface, where the tail and fuselage have continuous surfaces, where the surface of the tail is directly coupled to the surface of the fuselage. The vehicle further includes a sweepforward wing having a trailing edge and a rotor attached to the trailing edge of the sweepforward wing via a pylon, where the rotor has a maximum downward angle from the horizontal plane that is less than or equal to 60 degrees, and the STOL vehicle takes off and lands using at least some lift from the sweepforward wing and at least some lift from the rotor.

Description

[0001] Cross-references to other applications This application claims priority to U.S. Provisional Patent Application No. 62 / 912,872, filed on October 9, 2019, entitled “FIXED WING AIRCRAFT WITH TILT ROTORS,” which is incorporated herein by reference for all purposes. Background Art

[0002] New aircraft are being developed that can take off and land in dense urban areas, opening up new transportation corridors and avoiding congestion on the road. For example, Kitty Hawk is developing a new electric vertical take-off and landing (eVTOL) tiltrotor aircraft that can take off and land in a footprint of approximately 30 feet by 30 feet. Early prototypes have been built and tested, and further improvements in the performance of the vehicle (e.g., improved range) would be desirable. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various embodiments of the invention are disclosed in the following detailed description and accompanying drawings.

[0004] Figure 1A is a perspective view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors.

[0005] Figure 1B is a top view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors.

[0006] Figure 2A is a bottom view of an embodiment showing boundary layer thickness with the motor turned off.

[0007] Figure 2B is a bottom view of an embodiment showing boundary layer thickness with the motor turned on.

[0008] Figure 3A is a diagram illustrating an example of a tilt-wing configuration with corresponding lift vector, thrust vector, and drag.

[0009] Figure 3B is a diagram illustrating an example of a fixed wing configuration with a leading edge mounted tilt rotor and corresponding lift vector, thrust vector, and drag.

[0010] Figure 3C is a diagram illustrating an embodiment of a fixed wing configuration with a trailing edge mounted tilt rotor and corresponding lift vector, thrust vector, and drag.

[0011] Figure 4 is a diagram showing an embodiment of the airflow generated when a trailing edge mounted tilt rotor on a main wing is closed.

[0012] Figure 5 is a diagram showing an embodiment of a forward swept and tapered wing and a straight wing for comparison.

[0013] Fig. 6A is a diagram showing an embodiment of a takeoff tilt transition from a hovering position to a cruise position.

[0014] Figure 6B is a diagram showing an embodiment of a landing tilt transition from a cruise position to a hovering position.

[0015] Figure 7 is a diagram showing an embodiment of a velocity tilt map.

[0016] Figure 8 is a diagram showing an embodiment of a vehicle with a truncated fuselage that is capable of flying in a magic carpet mode.

[0017] Fig.9A is a top view showing an embodiment of a vehicle with a truncated fuselage and tail.

[0018] Fig. 9B is a side view showing an embodiment of a vehicle with a truncated fuselage and tail.

[0019] Fig. 10A is a side view showing an embodiment of a STOL vehicle with the rotor at a 30° position from the horizontal.

[0020] Fig. 10B is a perspective view showing an embodiment of a STOL vehicle with the rotor at a 30° angle from the horizontal.

[0021] Fig.11 is a side view showing a STOL vehicle with the rotor at 60° to the horizontal.

[0022] Fig.12 is a side view showing a STOL vehicle with the rotor at 60° to the horizontal. DETAILED DESCRIPTION

[0023] The present invention can be implemented in a variety of ways, including as: a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer-readable storage medium; and / or a processor, for example, a processor configured to execute instructions stored on a memory connected to the processor and / or provided by the memory. In this specification, these embodiments or any other form that the present invention may take may be referred to as technology. In general, within the scope of the present invention, the order of the steps of the disclosed process may be changed. Unless otherwise stated, a component described as being configured to perform a task (such as a processor or memory) may be implemented as a general component temporarily configured to perform a task at a given time or as a specific component manufactured to perform the task. As used herein, the term "processor" refers to one or more devices, circuits, and / or processing cores configured to process data (such as computer program instructions).

[0024] A detailed description of one or more embodiments of the present invention is provided below together with the accompanying drawings that illustrate the principles of the present invention. The present invention is described in conjunction with such embodiments, but the present invention is not limited to any embodiment. The scope of the present invention is limited only by the claims, and the present invention encompasses many alternatives, variations and equivalents. Many specific details are set forth in the following description in order to thoroughly understand the present invention. These details are provided for the purpose of example, and the present invention can be implemented according to the claims without some or all of these specific details. For the sake of clarity, technical materials known in the technical field related to the present invention are not described in detail so that the present invention is not unnecessarily concealed.

[0025] Various embodiments of a short takeoff and landing (STOL) vehicle are described herein. In some embodiments, the vehicle includes a tail having a surface and a fuselage having a surface, wherein the tail and the fuselage have a continuous surface, wherein the surface of the tail is directly coupled to the surface of the fuselage. This embodiment of the vehicle further includes a forward-swept wing having a trailing edge and a rotor attached to the trailing edge of the forward-swept wing via a pylon, wherein the rotor has a maximum downward angle with the horizontal plane that is less than or equal to 60°, and the STOL vehicle uses at least some lift from the forward-swept wing and at least some lift from the rotor to take off and land.

[0026] It may be helpful to first describe an early prototype of a tiltrotor vehicle, where the tiltrotor has a range of (substantially) 0°-90°. Then, various embodiments of a STOL vehicle are described.

[0027] Figure 1A is a perspective view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors. Figure 1B1 is a top view showing an embodiment of a forward-swept fixed-wing vehicle with tilt-rotors. In the example shown, the main wings (100a and 100b) are fixed wings that are attached to the fuselage (102a and 102b) in a fixed manner or position. In other words, the main wings are not tilt-rotors that can rotate. The main wings (100a and 100b) are also forward-swept (e.g., relative to the pitch axis). For example, for an aircraft embodiment with canard wings (as shown here), the forward sweep angle can be between about 14° and 16°. 掠 , or for an aircraft embodiment without canards, the forward sweep angle can be as high as 35°.

[0028] In this example, the main wings (100a and 100b) have six rotors (104a and 104b) attached to the trailing edge of the main wings. Rotors or propellers in this configuration are sometimes referred to as pusher propellers (e.g., because at least when the propellers are in their forward flight position, the propellers are behind the wings and "push" the vehicle forward). The forward flight mode is sometimes referred to as the cruise mode in this article. For clarity, these rotors on the main wings are sometimes referred to as main wing rotors (e.g., to distinguish them from rotors attached to canards). Of course, the number of rotors shown here is merely exemplary and is not meant to be limiting.

[0029] In addition to the six main wing rotors, there are two rotors (106a and 106b) attached to the canards (108a and 108b). These rotors are sometimes called canard rotors. The canards are thinner than the main wings, so unlike the main wing rotors, the canard rotors are attached to the far end of the canards, rather than to the trailing edge of the canards.

[0030] All rotors in this example are tilt-rotors, which means that they can tilt or otherwise rotate between two positions. In the accompanying drawings shown here, the rotors are in a cruising (e.g., forward flight, backward facing, etc.) position. In this position, the rotors rotate around (e.g., substantially) a longitudinal axis of rotation so that they provide (substantially) backward thrust. When the rotors are in this position, the lift that keeps the tilt-rotor vehicle in the air comes from the airflow above the main wing (100a and 100b) and the canard (108a and 108b). In this particular example, the rotation range of the tilt-rotor range has a minimum angular position of approximately 0°-5° and a maximum angular position of approximately 90°-95°. This range is specific to the design and / or implementation.

[0031] The rotors can also be tilted downward to be in a hovering (e.g., vertical takeoff and landing, downward facing, etc.) position (not shown). In this second position, the rotors rotate about a (e.g., substantially) vertical axis of rotation so that they provide (substantially) downward thrust. In this configuration, the lift that keeps the tilt-rotor vehicle airborne comes from the downward airflow of the rotors.

[0032] Generally speaking, the tiltrotors, when oriented to output thrust substantially downward, allow the aircraft to perform vertical takeoff and landing (VTOL). This mode or configuration (e.g., in terms of the manner in which the aircraft as a whole flies and / or in terms of the position of the tiltrotors specifically) is sometimes referred to as hovering. The ability to perform vertical takeoff and landing allows the aircraft to take off and land in areas without airports and / or runways. Once airborne, the tiltrotors (if desired) change position to output thrust (substantially) backward instead of downward. This allows the aircraft to fly in a more efficient manner for forward flight; this mode or configuration is sometimes referred to as cruising.

[0033] Canards are useful because they can stall first (e.g., before the main wings), thereby generating a large pitching moment and not losing much lift when stalled, whereas a main wing stall loses a large amount of lift for each change in pitch moment (e.g., causing the entire aircraft to drop or fall). Therefore, a stall with a canard may be more benign than without it. Canard stall behavior is particularly beneficial in conjunction with a forward-swept wing, because a stall of the main wing can generate an adverse pitching moment if at the wing root, and a large and dangerous rolling moment if at the wing tip. In addition, the canard can generate lift at low airspeeds and increase CL 最大 (ie, maximum lift coefficient), and a strut is provided to hold or otherwise attach the canard motor.

[0034] In some embodiments, the pylons (110a and 110b) for attaching the rotor to the canard and / or main wing include some hinges and / or rotation mechanisms so that the tilt rotor can rotate between the two positions shown. Any suitable hinge mechanism can be used. For example, for ultralight aircraft, there are very strict weight requirements, and therefore a lightweight solution may be desired. Alternatively, a fixed tilt solution can also be used to meet very strict weight requirements.

[0035] In some embodiments, the aircraft is designed so that the main wings (100a and 100b) and canards (108a and 108b) can provide sufficient lift to perform a glider-style landing if needed during an emergency. For example, some ultralight standards or specifications require the ability to land safely in the event of one or more rotor failures, and the ability to perform a glider-style landing would satisfy that requirement. One benefit of using a fixed wing for the main wing (e.g., as compared to a tilt-rotor wing) is that there is no danger of the wing getting stuck in the wrong position (e.g., a hovering position) where a glider-style landing is not possible because the wing position is not suitable for a glider-style landing.

[0036] Another benefit of a fixed wing with a trailing edge mounted tiltrotor is the stalling behavior (or lack thereof) during the transition from a hover position to a cruise position (or vice versa). With a tiltwing, during the transition, the angle of attack of the tiltwing changes, which increases the risk of stalling. A fixed wing with a trailing edge mounted tiltrotor does not change the wing angle of attack (e.g., even if the rotor is turned off / on or the tiltrotor is displaced). In addition, this configuration increases the dynamic pressure and circulation over the main wing, which greatly improves the behavior during the transition (e.g., from a hover position to a cruise position or vice versa). In other words, a fixed wing with a trailing edge mounted tiltrotor can perform transitions more quickly and / or more efficiently than a tiltwing (as an example).

[0037] Another benefit associated with a fixed-wing vehicle with a tiltrotor (e.g., compared to a tiltwing) is that a smaller fraction of mass is used for the tilt actuator(s). That is, the multiple actuators for the multiple tiltrotors (still) comprise a smaller fraction of mass than a single heavy actuator for the tiltwing. The tiltrotor also has fewer points of failure because there are multiple actuators compared to a single (and heavy) actuator for the tiltwing. Another benefit is that the fixed wing makes transitions (e.g., between a cruise mode or position and a hover mode or position) more stable and / or faster than a tiltwing design.

[0038] In some embodiments, the rotor is a variable pitch propeller having different blade pitches when the rotor is in a hovering position and a cruise position. For example, different blade pitches (ranges) can achieve more efficient operation or flight when in a cruise position and a hovering position. When the rotor is in a cruise position, adjusting the blade pitch to a "cruise pitch" (e.g., approximately 26°) achieves a lower frontal area (e.g., lower drag) that is beneficial to cruising. When the rotor is in a hovering position, adjusting the blade pitch to a "hover pitch" (e.g., approximately 6°) achieves a higher rotor disc area that is beneficial to hovering. In other words, one blade pitch may be very suitable for a cruise mode, but not for a hover mode, and vice versa. The use of a variable pitch propeller achieves better (e.g., overall) efficiency, resulting in less power consumption and / or increased flight range.

[0039] The following figure shows the Figure 1A and 1B Various benefits are associated with the exemplary aircraft shown in FIG.

[0040] Figure 2A 2 is a bottom view of an embodiment showing boundary layer thickness with the motor off. In this example, laminar flow extension lines 200a, 202a, and 204a show the extension of laminar flow at different regions of the main wing. In this example, it is assumed that the aircraft is cruising (e.g., flying in a substantially forward direction). Figure 1A and 1B As shown in , in this embodiment, the main wing rotor (206) is attached to the trailing edge of the main wing (208). The figure below shows the boundary layer thickness when the rotor is turned on.

[0041] Figure 2B is a bottom view of an embodiment showing boundary layer thickness with the motor on. In this example, the motor is on and the rotor has an exit air velocity of 30 m / s. With the motor on, a low pressure area is formed toward the rear of the wing, which increases the laminar extension over the main wing. For example, see the corresponding Figure 2A 200a, 202a and 204a in FIG. 200b, 202b and 204b. Comparison of the two groups shows that the laminar flow stretch increases in the first two positions (i.e., at 200a / 200b and 202a / 202b). The last position (i.e., 204a / 204b) has only a slightly longer laminar flow stretch due to interference from the canard rotor (210).

[0042] The drag from the main wing rotor (or more precisely, the drag from the pylons used to attach the main wing rotor to the main wing) is hidden in the wake of the airflow from the main wing. See, for example, Figure 2A , which more clearly shows that the pylon (220) is connected or otherwise attached to the rear of most of the laminar flow extension (222). For the embodiment shown here, the pylon is also able to remain away from some of the boundary layer thickness of the main wing, which means that the pylon has lower drag per unit surface area. This improves drag compared to some other alternative designs or configurations. The following figures describe this in more detail.

[0043] Figure 3A is a diagram showing an example of a tilt-wing configuration with corresponding lift vectors, thrust vectors, and drag. In this example, a fixed rotor (300) is attached to a tilt-wing (302) at a fixed position or angle. This is an alternative arrangement to the above-described aircraft embodiment(s). In order to direct the airflow generated by the fixed rotor (300) rearward or downward, the tilt-wing (302) rotates. As shown here, for this configuration, there is drag (304) at the trailing edge of the tilt-wing, which is undesirable.

[0044] Also shown here is the lift (306) and thrust (308) for this configuration, with the tilt-wing shown in the middle of a transition (e.g., between a cruise position and a hover position). As shown here, the lift (306) and thrust (308) are substantially orthogonal to each other, which is inefficient. In other words, the tilt-wing is inefficient during its transition.

[0045] Figure 3Bis a diagram showing an example of a fixed wing configuration with a leading edge mounted tiltrotor and corresponding lift vector, thrust vector and drag. In this example, the tiltrotor (320) is attached to the leading edge of the fixed wing (322). This is another alternative arrangement for the above-described aircraft embodiment(s). The corresponding drag (324) and thrust (326) for this arrangement are also shown. No useful lift is generated with this configuration, and therefore the lift vector is not shown here.

[0046] Figure 3C is a diagram showing an embodiment of a fixed wing configuration with a trailing edge mounted tiltrotor and corresponding lift vectors, thrust vectors, and drag. In this example, the tiltrotor (340) is attached to the trailing edge of a fixed wing (342). In this configuration, the drag due to the trailing edge mounted tiltrotor (e.g., primarily due to its pylon, not shown) is hidden in the wake of the airflow from the main wing. Thus, there is no drag (at least due to the tiltrotor (340)).

[0047] The position of the trailing edge mounted tilt-rotor (340) relative to the fixed wing (342) also draws air (344) over the fixed wing, after which the air turns or bends through the rotor and downward. This flow turning over the wing creates a relatively large induced lift (346), as shown here. Also shown here is the thrust vector (348) generated by the rotor. It should be noted that the induced lift (346) and the thrust (348) are substantially in the same direction (i.e., both are pointed substantially upward), which is a more efficient arrangement, including during transition. In other words, using a fixed wing with a trailing edge mounted tilt-rotor creates less drag and improved efficiency during transition (e.g., because the lift and thrust vectors are now pointed substantially in the same direction) compared to other rotor and wing arrangements. For example, please note that respectively Figure 3A and Figure 3B Resistance 304 and resistance 324, and Figure 3A The orthogonal positions of lift 306 and thrust 308 in FIG.

[0048] The following figures illustrate embodiments of flow diversion in more detail.

[0049] Figure 4 is a diagram showing an embodiment of airflow generated when a trailing edge mounted tiltrotor on a main wing is closed. In this example, a tiltrotor aircraft (400) is shown, but for comparison purposes, the main wing rotor is closed. With the rotor closed, the airflow inflow (402) and the airflow outflow (404) move substantially in the same direction. That is, the airflow does not turn (e.g., downward) as it passes over the rotor.

[0050] Tiltrotor 420 shows the same vehicle as tiltrotor 400, except that the rotors are open. In this example, the airflow inflow (422) and the airflow outflow (424) have significantly different directions, and there is a significant turn or bend in the airflow as it passes over the rotors of the exemplary tiltrotor shown. As described above, this causes significant lift, which is desirable because less power is consumed and / or the range of the tiltrotor is increased.

[0051] In this example, the main wing rotors (426) are in a hovering position. As shown here, these rotors are slightly pitched or otherwise tilted (e.g., with the top of the main wing rotor pointing slightly forward and the bottom pointing slightly backward). In this figure, the amount of tilt is shown as θ 俯仰 (428), and in some embodiments is approximately a 90° range of rotation or movement (e.g., ~3° upward from horizontal when in the cruise position (e.g., for minimum drag) and ~93° downward from horizontal when in the hover position, which yields a ~96° range of rotation). Although such canting or pitching of the rotors is not absolutely necessary for flow steering to occur, in some embodiments, the main wing rotors are canted or otherwise pitched to some extent to increase or otherwise optimize the amount of flow steering. In some embodiments, the canard rotors are similarly pitched. It should be noted that the tiltrotor 420 is shown in a nose-up position, and thus the vertical axis (e.g., relative to the tiltrotor) is not perpendicular to the ground and / or reference frame.

[0052] In some embodiments, when the rotor is in the hovering position, the rotor (e.g., main wing rotor and / or canard rotor) is slightly turned outward away from the fuselage or otherwise tilted. In some embodiments, the turning (e.g., outward) is about 10° to obtain greater yaw authority.

[0053] In some embodiments, the main wing, in addition to being forward swept, is also tapered (eg, the wing narrows outwardly toward the wing tip). The following figures describe various wing and / or tail embodiments.

[0054] Figure 5 5 is a diagram showing an embodiment of a swept and tapered wing and a straight wing for comparison. In the example shown, wing 500 is a straight wing without tapering (e.g., the wing is the same width from center to wing tip). An exemplary rotor (502) is shown at the trailing edge of the straight wing (500).

[0055] The center of thrust (504), indicated by the dashed line, is determined by the location or arrangement of the rotors and extends through the center of the main wing rotor (502). For simplicity, the canard rotors are ignored in this example. The center of lift is based on the shape of the wing. For a rectangular wing such as wing 500, the center of lift (506), indicated by the solid line, extends along the center of the wing. The calculation of the aerodynamic center is more complex (e.g., the aerodynamic center depends on the cross-section of the wing, etc.), and the aerodynamic center 508, indicated by the dashed line, is exemplary and / or typical for this type of wing.

[0056] As shown here, the arrangement of a straight wing (500) and its corresponding main wing rotor (502) creates a center of thrust (504) that is relatively far from both the center of lift (506) and the aerodynamic center. This separation is undesirable. More specifically, when the main wing rotor (502) is in a hovering position, if the center of thrust (504) is far from the center of lift (506), then the transition (e.g., in the context of the aircraft moving as a whole, such as switching from substantially upward flight to substantially forward flight, or vice versa) will produce very large moments and may capsize the vehicle or prevent acceleration or stability and / or require a bulky and / or non-optimal propulsion system. In cruise, if the center of thrust (504) is far from the center of lift (506), it is less important (e.g., because the thrust moment is smaller and more easily balanced by the aerodynamic moment), but it is still undesirable.

[0057] In contrast, the arrangement of a forward-swept and tapered wing (520) and its corresponding rotor (522) along the trailing edge produces a center of thrust (524), center of lift (526), ​​and aerodynamic center (528) that are closer to one another. For example, the forward sweep of the wing moves the rotor forward to varying degrees. This causes the center of thrust to move forward (e.g., toward the leading edge and toward the other centers). The tapering of the wing prevents the aerodynamic center and the center of lift from being displaced too far forward (and, more importantly, away from the center of thrust) due to the forward sweep. For example, for a forward-swept wing (not shown) without tapering, the center of thrust would move forward by approximately the same amount as the aerodynamic center and the center of lift, and would result in a greater separation between the three centers than is shown here in wing 520.

[0058] Some other benefits of a forward-swept and tapered wing include better visibility for the pilot, and a better location for the fuselage to main wing junction (e.g., allowing the main spar to pass behind the pilot's seat, rather than through the pilot). In addition, the taper reduces wing moments and brings the motor's center of thrust closer to the wing-to-fuselage attachment when referenced to the direction of flight, so there is less moment carried from the wing to the fuselage, a shorter tail boom (e.g., which reduces the weight of the aircraft), and improved pitch stability.

[0059] The following figures describe exemplary tilt transitions of the rotor between the cruise position and the hover position.

[0060] Fig. 6A is a diagram illustrating an embodiment of a takeoff tilt transition from a hover position to a cruise position. In some embodiments, an exemplary tiltrotor aircraft performs this transition shortly after takeoff (e.g., substantially vertically). It should be noted that this tilt transition is optional, and the aircraft can be flown entirely with the rotors in the hover position (although not at optimal performance). This may be done, for example, if a tilt maneuver is risky and is best performed at a higher altitude.

[0061] Tilt rotor 600 shows an exemplary aircraft after it performs a vertical takeoff. In this state shown here, the main wing rotor and the canard rotor are in a hovering position (e.g., rotating around a substantially vertical axis of rotation so that the rotor generates substantially downward thrust).

[0062] The tiltrotor then transitions from a completely upward direction of movement to a direction of movement with at least some forward motion, wherein the rotors continue in a hovering position until the tiltrotor reaches a certain desired altitude at which to begin the transition (602). In other words, the vehicle transitions first, and then changes the tilt of the rotors. In one example, the altitude at which the tiltrotor begins the change in rotor tilt from the hovering position to the cruise position is a sufficiently high altitude so that there is time to recover in the event of a problem during the transition. Switching the rotors between the hovering position and the cruise position is a riskier time, where the likelihood of problems (e.g., rotor failure, rotor jamming, etc.) is higher. Although the tiltrotor may have systems and / or techniques for recovery (e.g., compensating for rotor failure by causing the remaining rotors to output more thrust, deploying a parachute, etc.), these systems and / or techniques require time (i.e., sufficient altitude) to work.

[0063] From position 602, the tiltrotor aircraft flies substantially forward and moves the tiltrotors from a hovering position (e.g., wherein thrust is substantially output downward) to a cruise position. Once in cruise position 604, the rotors rotate about a substantially longitudinal axis so that they output rearward thrust.

[0064] Figure 6B is a diagram illustrating an embodiment of a landing tilt transition from a cruise position to a hover position. For example, an exemplary tiltrotor aircraft may perform this transition prior to a vertical landing. As with the previous transitions, this transition is optional. For example, if desired, an exemplary tiltrotor aircraft may maintain the tiltrotor in a cruise position and perform a glider-style landing instead of a vertical landing.

[0065] Tiltrotor 610 shows the rotor in a cruise position. When flying in a substantially forward direction, the tiltrotor moves from the cruise position shown at 610 to a hovering position shown at 612. With the tiltrotor in the hovering position (612), the tiltrotor descends to position 614 (at least in this example) with some forward movement, thereby keeping power usage (much) lower and retaining better options in the event of a motor or other component failure (e.g., the tiltrotor can add power to the rotor and exit the landing process or path) until it finally lands on the ground.

[0066] Figure 7 700 is a diagram illustrating an embodiment of a velocity-tilt graph. In the illustrated diagram, the x-axis illustrates the forward velocity of the aircraft, and the y-axis illustrates the tilt (e.g., the position or angle of the tilt-wing or tilt-rotor) ranging from a (e.g., minimum) cruise position (700) to a (e.g., maximum) hover position (702).

[0067] The first operational envelope (704), shown with a solid line border and filled with a grid pattern, is associated with a tilt-rotor aircraft. Figure 4 The tiltrotor 400 and Figure 3A 302 and fixed rotor 300 in FIG. 2. A second operational envelope (706), shown with a dashed border and gray fill, is associated with a (e.g., similar) aircraft having a forward-swept and fixed wing with a trailing-edge mounted tilt-rotor. See, for example, the above embodiments.

[0068] In the diagram shown here, the tiltrotor operating envelope (706) is a superset of the tiltrotor operating envelope (704), indicating that the former aircraft configuration is safer and / or more airworthy than the latter, and is also able to fly faster and slower at similar tilt positions. For fixed wings, the wings are already (and / or always) pointed in the (forward) direction of travel. When the tiltrotor is in or near the (e.g., maximum) hover position (702), the vehicle can fly almost all the way to the stall speed (e.g., V2) without having to tilt the motor up to the cruise position. It should be noted that, for example, the tiltrotor operating envelope (706) can stay in the (e.g., maximum) hover position (702) until V2. This greatly increases the operating states of the tiltrotor operating envelope (706) compared to the tiltrotor operating envelope (704). For example, please note all the gray areas above the tiltrotor operating envelope (704).

[0069] Another effect that may contribute to the extended operating envelope of a tiltrotor configuration in or near a hover position includes flow steering (see, e.g., Figure 4). The flow turning over the main wing causes some additional lift. In some embodiments, this flow turning and the lift it produces is amplified or optimized by tilting the main wing rotors from directly downward to a slightly backward angle when in normal hover (e.g., in the minimum tilt position 700).

[0070] In contrast, the tilt-wing presents a larger frontal area when it is tilted upward in the (e.g., maximum) hover position (702). Therefore, the tilt-wing cannot fly forward at any suitable speed until it is in or near the full (e.g., minimum) cruise position (700) or nearly so.

[0071] The exemplary vehicle described above is designed for vertical takeoff and landing. However, vertical takeoff and landing (i.e., hover mode) is a very energy-intensive flight mode. By modifying the VTOL vehicle to instead perform short takeoff and landing (STOL), the vehicle's range can be increased. In order to adapt the vehicle to STOL operations, the range of the tilt rotor is limited to an angle significantly less than the 90° associated with hovering. The following figures describe various embodiments thereof.

[0072] Figure 8 is a diagram showing an embodiment of a vehicle with a truncated fuselage that is capable of flying in a magic carpet mode. As used herein, the term "magic carpet mode" refers to a mode in which the rotors are still in a hovering orientation, but the vehicle has been accelerated to an airspeed at which a large amount of lift is generated by the wings. In magic carpet mode, vehicle speed can be controlled by pitching forward, altitude and can be controlled by increasing speed to gain efficiency and therefore climb rate, or by adding thrust directly to the rotors. In the example shown, the vehicle has a canard (800) with two canard rotors (802), only one of which is shown. The main wing (804), which is a fixed wing with forward sweep, has six main rotors (806) attached to the trailing edge of the main wing, only half of which is shown. The fuselage (808) is relatively short and is referred to herein as a truncated fuselage. For example, note that the end of the fuselage (810) extends only a little beyond the end of the rearmost rotor (812). In this particular embodiment, the rotors are fixed and do not tilt or otherwise change position.

[0073] There are a variety of vehicle embodiments that can meet stringent weight requirements (e.g., ultralight standards). In this approach, the truncated fuselage is much shorter and has no tail per se, both of which keep weight low. The use of fixed rotors (e.g., as compared to tilt-rotors) can also keep weight low. The truncated fuselage and lack of a tail also create a smaller footprint, which aids in transportation (e.g., in a trailer) and the amount of space required for takeoff and / or landing.

[0074] In some embodiments, the rotors in a fixed position are tilted rearward, more at the hover end of the tilt spectrum than at the cruise end of the tilt spectrum (e.g., an axis of rotation tilted downward from the horizontal at an angle between 20° and 40° (inclusive)). See, for example, axis of rotation (820) associated with a fixed rotor (822), where the tilt angle is between 20° and 40°, which is suitable and / or acceptable for a magic carpet mode. For example, this rotor position (although fixed) allows the exemplary vehicle to fly vertically (e.g., not due to aerodynamic lift on the wing, but from airflow generated by the rotor) as well as fly forward (e.g., away from the wing). This ability or mode to maintain the rotors in a hovering tilt while flying (e.g., primarily and / or mostly) in a wing-lift manner is sometimes referred to as a flying magic carpet mode. It should be noted that this ability to fly in a magic carpet mode is not necessarily limited to fixed rotor embodiments. For example, some or all of the above-described tiltrotor embodiments may be capable of flying in a magic carpet mode (eg, where the tilt position is an extreme or maximum hover position, or some tilt position between the two extremes).

[0075] Fig.9A is a top view showing an embodiment of a vehicle with a truncated fuselage and tail. Figure 8 The previous vehicle embodiment shown has similarities and for the sake of brevity, the shared features are not discussed here. Unlike the previous example, this embodiment has a tail (900). The fuselage (902a) is a truncated fuselage, so the tail (900) and the fuselage (902) are connected using beams (904a).

[0076] Fig. 9B is a side view showing an embodiment of a vehicle with a truncated fuselage and tail. Fig. 9B Continued Fig.9A From this view, the truncated fuselage (902b) and beams (904b) are shown, and other features of the vehicle are more clearly shown, including the horizontal control surfaces (906) and vertical control surfaces (908) on the tail and the ski-type landing gear (910).

[0077] In some applications, Figure 8-9B The truncated fuselage vehicle shown in may be undesirable (for reasons described in more detail below). The following figures show various embodiments of STOL vehicles that may be more desirable in such applications.

[0078] Fig. 10A is a side view showing an embodiment of a STOL vehicle with the rotor at a 30° position from the horizontal. Fig. 10B1 is a perspective view showing an embodiment of a STOL vehicle with the rotors in a position 30° from the horizontal. In the example shown here, the canard rotors (1000a and 1000b) and the main wing rotors (1002a and 1002b) are in a position 30° from the horizontal cruising position.

[0079] In some embodiments, the rotors (1000a, 1000b, 1002a and 1002b) do not tilt and are fixed in the position shown here (i.e., 30°). Alternatively, in some other embodiments, the rotors can tilt between a horizontal cruise position (i.e., 0°) and the position shown here (i.e., 30°). In either case, the vehicle is not configured for vertical takeoff and landing, but instead uses a (short) runway for short takeoff and landing (e.g., 200 feet). In some applications, there is room for a short runway, and the (cruise) range extension provided by a STOL vehicle is attractive. In some applications, there is runway space, but there is no 200 feet of runway space. Using a tilt angle below 30° will reduce the runway length (but will also affect the vehicle's range and maximum speed).

[0080] In Figures 10A-10B The benefit of the rotors in the position shown is that they increase the dynamic pressure from the main wing rotors (1002a and 1002b) above the main wing (1004), thereby producing a higher lift coefficient (e.g., Figure 1A and Figure 1B In other words, takeoff and landing of a STOL vehicle can be more efficient than takeoff and landing of a similar VTOL vehicle, thus requiring less power from the drive train. In terms of thrust-to-weight ratio, the exemplary STOL vehicle requires about half of what a similar VTOL vehicle requires to take off or land.

[0081] Another benefit is that a smaller and lighter power train can be used for an exemplary STOL vehicle compared to a similar VTOL vehicle due to the reduced power demand on the power train during takeoff and landing. This weight reduction can be used to carry more payload or more batteries (e.g., to extend the range while keeping the total weight essentially the same). For example, if additional batteries are added to a STOL vehicle, a ~25% increase in cruise range can be achieved.

[0082] If the rotors or propellers are fixed, additional weight savings can be achieved. For fixed rotors, the tilt mechanism can be removed. If this additional weight savings is used (still) for more batteries, the range can be increased by ~30%-35% over a similar VTOL vehicle.

[0083] In some embodiments, due to the reduced power requirements associated with short takeoff and landing compared to vertical takeoff and landing, the rotor is relatively simple to operate relative to a similar VTOL vehicle (e.g., Figure 1A and 1B ) size reduction (e.g., smaller blades and smaller motors and power electronics for the motors). This can be attractive because, in addition to saving weight, better packaging can be achieved due to smaller components, which reduces drag and also reduces the space required for cargo (e.g., because the overall vehicle width is narrower).

[0084] In some embodiments, the blade pitch angle(s) (range) of the STOL rotor is adjusted due to a more restrictive pitch angle(s) (range) (e.g., compared to a similar VTOL vehicle). For example, for a fixed rotor, an optimal blade pitch angle may be selected for the fixed tilt position. Alternatively, if the rotor is a tilt rotor, the range of blade pitch angles may be reduced and / or adjusted due to a reduced range of kinematic tilt positions (e.g., where the maximum tilt position is in the range of 20°-40°, or 30°-60°).

[0085] and Figure 8-9B Unlike the truncated fuselage vehicle shown in Figures 10A-10B The STOL vehicle shown in has a full length fuselage (1008a and 1008b) directly coupled to the tail (1006a and 1006b), rather than a truncated fuselage coupled to the tail via a beam. Another way to describe this is that the surface of the tail meets or contacts the surface of the fuselage (directly) so that there is no surface discontinuity (e.g., due to the beam). This surface continuity may be desirable for aerodynamic reasons. Due to the different configurations, there may be different tilt angle ranges applicable to different configurations, as well as different flight methods, performance characteristics, and / or associated benefits. In some applications, Figure 10A-10B The STOL vehicle shown in Figure 8-9B The truncated fuselage vehicle shown in FIG. 1 is more attractive. For example, due to the passive stability of the exemplary STOL vehicle, its use in manned applications may be more attractive because the control system does not need to be certified to the same level of redundancy and / or robustness. In the event of a system failure, the STOL vehicle can still be controlled by the pilot during cruise without an automatic control system, and the vehicle can be landed via conventional landing means.

[0086] The following figures illustrate STOL vehicles with rotors at various tilt positions and / or angles and runway lengths, ranges, and maximum speeds associated with those embodiments.

[0087] Fig.111 is a side view of a STOL vehicle with the rotors at a 60° position from the horizontal. In this example, the canard rotor (1100) and the main wing rotor (1102) are at a 60° position from the horizontal cruise position. In various embodiments, the rotors are tilt rotors or fixed rotors.

[0088] Fig.12 1 is a side view of a STOL vehicle with the rotors at a 60° position from the horizontal. In this example, the canard rotor (1200) and the main wing rotor (1202) are at a 45° position from the horizontal cruise position. As described above, in various embodiments, the rotors are tilt rotors or fixed rotors. Table 1: Corresponding to Figure 10A-Figure 12 The range values ​​assume that the drive train of the STDL saves weight, which allows the STOL vehicle to carry more batteries than a similar VTOL vehicle.

[0089] Table 1 shows Figure 10A-Figure 12 Various (eg performance) indicators and / or characteristics of the different (maximum) tilt angles shown in . Of course, depending on the application and / or performance indicators of interest, different (maximum) tilt angles are more attractive than other tilt angles.

[0090] In some embodiments, a common or shared code base of a flight computer is used for various embodiments described above, including fixed rotors and tilt rotors. For example, for safety and / or certification reasons, it may be desirable to maintain a single code set for a flight computer. In one example, there is a (e.g., global) parameter or setting associated with a tilt range. For example, for a fixed rotor at 30°, the range is [30°, 30°], but for a tilt rotor with a maximum tilt angle of 60°, the range is [0°, 60°] (e.g., where 0° is the rotor in a cruise (i.e., forward flight) position). This global parameter is propagated throughout and is used by the flight computer (code) to determine (as an example) a rotor thrust control signal to achieve the desired force and torque within a given allowed tilt angle range. For example, the allowed range will first be used to limit the actuator authority database, and then be used to determine which (flight) modes (e.g., hovering or STOL takeoff and landing) are allowed. The controller can then use the subset of available modes and an actuator authority map or database to determine how to best distribute actuator usage throughout flight (e.g., during thrust distribution to generate motor control signals for motor controllers). Using the same code base can also make it easier to support fleets of configurable vehicles that can be reconfigured as needed (described in more detail below).

[0091] In some embodiments, it may be desirable to have a fleet of configurable vehicles that can be reconfigured as needed (e.g., based on current demand and / or flight application). In some embodiments, this allows the vehicle to be configured for VTOL as needed (e.g., based on current demand and / or flight application). Figure 1A and Figure 1B ) or STOL (e.g., according to Fig. 10A -- Fig.12 ). In some embodiments, in order to change the (maximum) tilt angle, the rotor may include a physical device to limit the (maximum) tilt angle, such as hard stops of different sizes. In some embodiments, the STOL and VTOL configurations are accomplished purely via software limitations (e.g., setting parameters associated with the allowed tilt angle range).

[0092] In some embodiments, the vehicle includes modular and / or replaceable sections so that sections more suitable for VTOL vs. STOL or fixed rotor vs. tilt rotor can be supported. For example, the brackets supporting the tilt mechanism and motors may not be bonded to the carbon structure, but instead may be bolted to a support frame that is in turn bonded to the structure. This would allow a tilt-hinged mounted rotor to be replaced with a fixed angle rotor relatively quickly. While the weight associated with such a setup would be greater than a configuration that could not be easily changed, the ability to use a common fleet may offset this in some cases.

[0093] Various embodiments of STOL vehicles have been described herein, but these examples are merely exemplary and are not intended to be limiting. In various embodiments, the vehicle includes a tandem wing or single wing arrangement designed for STOL operations, which can be used for long-range applications with a vehicle size ranging from a single-person vehicle size to a size similar to a feeder aircraft. In some such embodiments, the tilt will be limited to 45 °-60 ° (i.e., forward flight configuration) with the horizontal plane. Although a runway is required to land, they can be greatly shortened (e.g., as short as 100-200 feet). This allows flights to and from smaller airports or even larger heliports with sufficient available space. In some applications, such a vehicle is used for (e.g., dedicated) flights to and from entities (e.g., universities or enterprises) with sufficiently large parks. A flap effect is produced by limiting the tilt to (e.g.) 45 °-60 °, thereby allowing the main wing to generate higher lift without stalling due to the induced airflow of the propeller.

[0094] Although the foregoing embodiments have been described in detail for the purpose of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways to implement the invention. The disclosed embodiments are illustrative rather than restrictive.

Claims

1. A vehicle, comprising: A tilt-rotor located at the rear of the wing and attached to the wing via a pylon, where: The tiltrotor has an adjustable maximum downward angle of less than or equal to 60° relative to the horizontal plane; The maximum adjustable downward angle is set by a setting associated with the flight computer; and The vehicle takes off and lands using at least some amount of lift from the wings and at least some amount of lift from the tiltrotors; and The flight computer is configured to instruct the tiltrotor to produce a new maximum downward angle in response to a change to the maximum downward angle adjustable by a setting associated with the flight computer, including by: updating an actuator authority database associated with the flight computer to reflect the new maximum downward angle; and Rotor control signals are generated for the tiltrotor using an updated actuator authority database reflecting the new maximum downward angle.

2. The carrier according to claim 1, wherein: The wing comprises a forward swept and tapered wing.

3. The carrier according to claim 1, wherein: The tiltrotor includes a plurality of hard stops corresponding to different maximum downward angles.

4. The carrier according to claim 1, wherein: The tiltrotor is rotatable between a cruise position and an adjustable maximum downward angle.

5. The carrier according to claim 1, wherein: The new maximum downward angle is determined based at least in part on a length of the runway.

6. The carrier according to claim 1, wherein: The new maximum downward angle is determined based at least in part on a desired range for the vehicle.

7. The carrier according to claim 1, wherein: In response to the change in the adjustable maximum downward angle, the flight computer further updates a set of allowed flight modes associated with the flight computer to reflect the new maximum downward angle.

8. The carrier according to claim 1, wherein: The new maximum downward angle is 90°; and In response to the change in the adjustable maximum downward angle, the flight computer updates a set of permissible flight modes associated with the flight computer to include a hover flight mode.

9. A method comprising: A tiltrotor is provided located at the rear of the wing and attached to the wing by a pylon, wherein: The tiltrotor is included in the vehicle; The tilt rotor has an adjustable maximum downward angle less than or equal to 60° from the horizontal plane; The maximum adjustable downward angle is set by a setting associated with the flight computer; and The vehicle takes off and lands using at least some amount of lift from the wings and at least some amount of lift from the tiltrotors; and Providing a flight computer configured to instruct a tiltrotor to produce a new maximum downward angle in response to a change to the maximum downward angle adjustable by a setting associated with the flight computer, including by: updating an actuator authority database associated with the flight computer to reflect the new maximum downward angle; and Rotor control signals are generated for the tiltrotor using an updated actuator authority database reflecting the new maximum downward angle.

10. The method according to claim 9, wherein: The wing comprises a forward swept and tapered wing.

11. The method according to claim 9, wherein: The tiltrotor includes a plurality of hard stops corresponding to different maximum downward angles.

12. The method according to claim 9, wherein: The tiltrotor is rotatable between a cruise position and an adjustable maximum downward angle.

13. The method according to claim 9, wherein: The new maximum downward angle is determined based at least in part on a length of the runway.

14. The method according to claim 9, wherein: The new maximum downward angle is determined based at least in part on a desired range for the vehicle.

15. The method according to claim 9, wherein: In response to the change in the adjustable maximum downward angle, the flight computer further updates a set of allowed flight modes associated with the flight computer to reflect the new maximum downward angle.

16. The method of claim 9, wherein: The new maximum downward angle is 90°; and In response to the change in the adjustable maximum downward angle, the flight computer updates a set of permissible flight modes associated with the flight computer to include a hover flight mode.

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