Patent Description:
This disclosure is related to wing-in-ground effect vehicles (WIGs) and, more particularly, to systems and methods directed toward WIGs designed to operate for significant distances in water before takeoff and after landing.

WIGs can include a propulsion source and an aerodynamic surface which is designed to operate close to the ground or water surface in aerodynamic ground-effect. The primary reason for operation in aerodynamic ground-effect is the increase in flight efficiency resulting from the decrease in the induced drag of the wing.

For instance, <CIT> relates to a hydrofoil vehicle capable of achieving a hullborn, foilborn and airborne mode of operation, and transitions between such modes driver controlled or automatic. Mode selection is based on the desired forward speed.

The object of the present invention is to provide a craft and method allowing for safe transition between moving modes.

This object is solved by the present invention as defined in the independent claims.

The drawings are for the purpose of illustrating example embodiments, and it is to be understood that the present disclosure is not limited to the arrangements and instrumentalities shown in the drawings.

The example WIGs described herein include features designed to create a more comfortable passenger experience and wider environmental operating range compared to existing WIGs. Advantages may include, but are not limited to, more comfortable takeoff and landing maneuvers, a smaller turning radius, a higher cruise efficiency, increased flight stability and safety, decreased operating costs, and the ability to operate comfortably in high seas and at low speeds in crowded harbors. The WIGs described herein are designed to fly over bodies of water and can therefore be used for transporting people and/or cargo between coastal destinations or between shore and offshore infrastructure. The WIGs can emit zero emissions during operation by utilizing an all-electric drivetrain that sources energy from a battery or hydrogen fuel cell system.

The WIGs described herein are configured to operate in at least three different operational modes including a first waterborne mode in which the hull of the WIG is at least partially submerged in water, a second waterborne mode in which the hull of the WIG is elevated above the water while one or more hydrofoils of the WIG are at least partially submerged in water, and an airborne mode in which the entire WIG is elevated above the water in ground-effect flight. Unlike existing vehicles, the WIGs described herein may operate in each of these three modes over extended distances and times.

In order to provide such improvements over existing vehicles, the WIGs described herein can combine multiple different technologies including (i) an electric powertrain in a distributed blown-wing configuration, (ii) a retractable hydrofoil system, (iii) digital flight control systems for stabilizing the WIG and controlling an altitude of the WIG near a water surface, and (iv) control systems for detecting and avoiding maritime traffic and obstacles. These technologies are explained in further detail below.

<FIG> depict different views of an example WIG <NUM>, including a perspective view in <FIG>, a top view in <FIG>, a side view in <FIG>, and a front view in <FIG>. As shown in these various views, the WIG <NUM> includes a hull <NUM>, a main wing <NUM>, a tail <NUM>, a main hydrofoil assembly <NUM>, and a rear hydrofoil assembly <NUM>.

In line with the discussion above and as further described below, the WIG <NUM> is capable of operating in a first waterborne mode for extended periods of time, during which the hull <NUM> is at least partially submerged in water. As such, the hull <NUM> may be designed to be watertight, particularly for surfaces of the hull that contact the water during this first waterborne operational mode. Further, the hull <NUM>, as well as the entirety of the WIG <NUM>, is configured to be passively stable on all axes when floating in water. To help achieve this, the hull <NUM> may include a keel (or centerline) <NUM> which may provide improved stability and other benefits described below. And in some examples, the WIG <NUM> may include various mechanisms for adjusting the center of mass of the WIG <NUM> so that the center of mass aligns with the center of buoyancy of the WIG <NUM>. One way to achieve this is to couple a battery system (described in further detail below in connection with <FIG>) of the WIG <NUM> to one or more moveable mounts that may be moved by one or more servo motors or the like. A control system of the WIG <NUM> may detect a change in its center of buoyancy, for instance by detecting a rotational change via an onboard gyroscope, and the control system may responsively operate the servo motors to move the battery system until the gyroscope indicates that the WIG <NUM> has stabilized. Another way to adjust the center of mass of the WIG <NUM> so that the center of mass aligns with the center of buoyancy of the WIG <NUM> is to include a ballast system for pumping water or air to various tanks distributed throughout the hull <NUM> of the WIG <NUM>, which may allow for adjusting the center of mass of the WIG <NUM> in a similar manner as moving the battery system. Other example systems may be used to control the center of mass of the WIG <NUM> as well.

Additionally, the hull <NUM> may be designed to reduce drag forces when both waterborne and airborne. For instance, the hull <NUM> may have a high length-to-beam ratio (e.g., greater than or equal to <NUM>), which may help reduce hydrostatic drag forces when the WIG <NUM> is under forward waterborne motion. In some examples, the keel <NUM> may be curved or rockered to improve maneuverability when waterborne. Further, the hull <NUM> may be designed to pierce the surface of waves (e.g., to increase passenger and crew comfort) by including a narrow, low-buoyancy bow portion of the hull <NUM>.

The main wing <NUM> may also include features to improve stability of the WIG <NUM> during waterborne operation. For instance, as shown in <FIG>, the main wing <NUM> may include an outrigger <NUM> at each end of the main wing <NUM>. The outriggers <NUM> (which are sometimes referred to as "wing-tip pontoons") are configured to provide a buoyant force to the main wing <NUM> when submerged or when otherwise in contact with the water. As depicted in the front view of the WIG <NUM> in <FIG>, the main wing <NUM> may be designed to have a gull wing shape such that the outriggers <NUM> at the ends of the main wing <NUM> are at the lowest point of the main wing <NUM> and are positioned approximately level with (or slightly above) a waterline of the hull <NUM> when the hull <NUM> is waterborne.

As best shown in the top view of the WIG <NUM> in <FIG>, the main wing <NUM> is designed to have a high aspect ratio, which represents the ratio of the span of the main wing <NUM> to the mean chord of the main wing <NUM>. In some examples, the aspect ratio of the main wing <NUM> is greater than or equal to five, or greater than or equal to six, but other example aspect ratios are possible as well.

High aspect ratio wings may provide certain drawbacks when compared to low aspect ratio wings, including reduced pitch stability due to a shorter mean chord. Previous WIGs have opted for low aspect ratio wings to address these instability issues. For instance, when a WIG is flying in ground-effect, there is an increase in static pressure underneath the wings, which shifts the aerodynamic center of the WIG backward and causes aerodynamic instability in the WIG's pitch axis. Low aspect ratio wings focus the lift force on the leading edge of the wing, and when the WIG pitches upward the leading edge also pitches upward, causing the WIG to leave ground-effect, lose lift, and settle back down. However, while this low aspect ratio wing design addressed instability issues, it significantly reduced the aerodynamic efficiency of these previous WIG designs.

Another drawback of high aspect ratio wings, generally, is their reduced maneuverability due to a lower roll angular acceleration. And the maneuverability of high aspect ratio wings may be further reduced for WIGs. For instance, when operating in a ground-effect flight mode over a water surface, a WIG with a high aspect ratio wing may be close enough to the water surface that too much roll could cause the wing to collide with the water surface. To address these and other issues, the WIG <NUM> disclosed herein may include various additional mechanisms, as described in further detail below, for improving its maneuverability to compensate for the reduced maneuverability resulting from the high aspect ratio of the main wing <NUM>.

While high aspect ratio wings may provide various drawbacks, such as those identified above, high aspect ratio wings may also provide a number of improvements over low aspect ratio wings, including increased roll stability and increased efficiency resulting from higher lift-to-drag ratios. Further, another benefit of a high aspect ratio wing is that it provides a longer leading edge for mounting a distributed propulsion system along the wing. Arranging propulsion systems in this distributed manner along the wing provides a "blown-wing" propulsion system in which the propulsion systems can increase the velocity of air moving over the wing, and the increased air velocity over the main wing increases the lift generated by the main wing. This increase in lift can enable the WIG to takeoff and become airborne at slower speeds, which can be especially advantageous for takeoff of waterborne WIGs. For instance, waterborne WIGs may be subjected to various forces that limit their takeoff speed, such as water resistance and reduced lift caused by cavitation when operating on one or more hydrofoils, as explained in further detail below.

Previous WIG designs have typically incorporated low aspect ratio wing designs, such as inverse-delta wing designs. Such low aspect ratio wings have been used to increase the pitch stability of the WIG when flying in ground effect. In connection with low aspect ratio wings, previous WIG designs have also incorporated various ram-air methods that involve using the primary propulsion system to push air under the WIG between the wing and the water surface to artificially create additional lift.

Unlike previous designs that have used ram-air methods to assist with takeoff, the WIG <NUM> disclosed herein incorporates a distributed blown-wing propulsion system that assists with takeoff by allowing for slower takeoff speeds. As shown in <FIG>, the main wing <NUM> includes a number of electric motor propeller assemblies <NUM> distributed across a leading edge of the main wing <NUM>. Arranging the propeller assemblies <NUM> in this manner can increase the velocity of air moving over the main wing <NUM>, and the increased air velocity over the main wing <NUM> increases the lift generated by the main wing <NUM>. This increase in lift can enable the WIG <NUM> to take off and become airborne at slower vehicle speeds.

The distributed blown-wing arrangement of the electric motor propeller assemblies <NUM> improves upon arrangements in existing WIGs, which have relied on one or more liquid-fueled engines as the primary propulsion source during operation. Liquid-fueled engines are typically much heavier, more complex, and larger than electric motors, so any benefits of additional lift provided by a distributed blown-wing arrangement of liquid-fueled engines may be outweighed by the additional weight and complexity of multiple engines. Further, coupling an array of propellers to the liquid-fueled engines may require multiple rotating shafts and gearboxes, thereby increasing the mechanical complexity and resultant maintenance costs to the point of unfeasibility. Using the electric motor propeller assemblies <NUM>, however, alleviates such issues. Each individual electric motor propeller assembly <NUM> can be controlled by an electronic speed controller and powered by an onboard battery system, such as, for example, a lithium-ion, magnesium-ion, or lithium-sulfur system, or by some other onboard electrical supply system, such as a fuel cell or a centralized liquid-fueled electricity generator. In some examples, the onboard electrical supply system may include multiple systems for supplying power during different operational modes, such as a first battery system configured to deliver large amounts of power during takeoff and a second system with a higher energy density but lower peak power capability for delivering sustained lower power during cruise operation (e.g., during hydrofoil waterborne operation or during airborne operation, each of which are described in further detail below).

An example onboard battery system <NUM> is depicted in <FIG>. As shown, the battery system <NUM> may be arranged in a protected area <NUM> of the hull <NUM> below a passenger seating area <NUM>. The battery system <NUM> may be separated from the passenger seating area <NUM> by a firewall <NUM> to protect the passengers from harm if a thermal runaway occurs. In some examples, additional or alternative protective measures may be taken as well. For instance, the WIG <NUM> may include one or more mechanisms for flooding the battery system <NUM> upon detecting a thermal runaway or a fire in the protected area <NUM>. In order to flood the battery system <NUM>, the WIG <NUM> may include a battery management system comprising voltage and/or thermal sensors for detecting thermal runaway or some other fire detection system for detecting a fire in the protected area <NUM>. Further, the hull <NUM> may include one or more valves or other controllable openings in the hull <NUM>. Responsive to detecting a fire in the protected area <NUM> or thermal runaway in the battery system <NUM>, a control system of the WIG <NUM> may open the valves or other controllable openings in the hull <NUM> to expose the protected area <NUM> and the battery system <NUM> to the water in which the WIG is floating.

A water-based flooding system as described above would only work while the WIG <NUM> is waterborne, so other measures may be taken to account for fires or thermal runaway during airborne operation. As one example, any controllable openings in the hull <NUM> may be configured to be large enough to jettison the battery system <NUM> out of the hull <NUM> through the openings. The battery system <NUM> may be configured such that the weight of the battery system <NUM> provides sufficient force to jettison the battery system <NUM> out of the hull <NUM> when the hull <NUM> is opened, or the WIG <NUM> may include an actuator or some other mechanism to jettison the battery system <NUM> out of the hull <NUM>. As another example, the WIG <NUM> may include an inert gas fire suppression system for reducing the amount of oxygen in the protected area <NUM> and suppressing any fires in response to detecting a fire in the protected area <NUM> or thermal runaway in the battery system <NUM>. Other examples are possible as well.

In other examples, the WIG <NUM> may take measures to become waterborne in response to detecting a fire in the protected area <NUM> or thermal runaway in the battery system <NUM>. For instance, responsive to making such a detection, the control system of the WIG <NUM> may determine an operational state of the WIG <NUM>, including whether the WIG <NUM> is operating in a hull-borne mode, a hydrofoil-borne mode, or a wing-borne mode (each of which are described in further detail below). In response to determining that the WIG <NUM> is operating in a hull-borne mode, the control system may flood the battery system <NUM> upon detecting a thermal runaway or a fire in the protected area <NUM> as described above. If, however, the control system determines that the WIG <NUM> is operating in a hydrofoil-borne mode or a wing-borne mode, the control system may cause the WIG <NUM> to transition to the hull-borne mode upon detecting a thermal runaway or a fire in the protected area <NUM> and then flood the battery system <NUM>. Techniques for transitioning between operational modes are described in further detail below in connection with <FIG>.

The positioning of the electric motor propeller assemblies <NUM> along the leading edge of the main wing <NUM> may be determined based on a variety of factors including, but not limited to, (i) the required total thrust for all modes of operation of the WIG <NUM>, (ii) the thrust generated by each individual propeller assembly <NUM>, (iii) the radius of each propeller in the respective propeller assemblies <NUM>, (iv) the required tip clearance between each propeller and the surface of the water, and (v) the additional freestream velocity over the main wing <NUM> required for operation. As shown in <FIG>, the number of propeller assemblies <NUM> is symmetrical across both sides of the hull <NUM>. The propeller assemblies <NUM> may all be identical, or they may have different propeller radii or blade configurations along the span so long as the configuration is symmetrical across the hull <NUM>. One advantage for having different propeller assembly <NUM> radii is allowing adequate propeller tip clearance from the water or vehicle structure. An advantage of having different blade configurations on the propeller assemblies <NUM> is to allow some propellers to be optimized for different operational conditions, such as airborne cruise. The propeller placement and configuration may vary to increase the airflow over the main wing <NUM> or tail system <NUM> to improve controllability or stability. While <FIG> depict an example WIG <NUM> having eight total propeller assemblies <NUM>, the actual number of propeller assemblies <NUM> can vary based on the requirements of the WIG <NUM>.

In some examples, the respective propeller assemblies <NUM> may have different pitch settings or variable pitch capabilities based on their position on the main wing <NUM>. For instance, a subset of the propeller assemblies <NUM> may have fixed-pitch propellers sized for cruise speeds, while the remainder of the propeller assemblies <NUM> can have fixed-pitch propellers configured for takeoff, or can allow for varying of the propeller's pitch. Additionally, different propeller assemblies <NUM> may be turned off or have reduced rotational speeds during different modes of operation. For instance, during waterborne operation, one or more of the propeller assemblies <NUM> may be turned off or have reduced rotational speeds in a manner that generates asymmetrical thrust. This may create a yawing moment on the WIG <NUM>, allowing the WIG <NUM> to turn without large bank angles and increasing the turning maneuverability of the WIG <NUM>. For instance, in order to yaw right, the WIG <NUM> may increase the rotational speeds of the propellers of one or more of propeller assemblies 116e-h while decreasing the rotational speeds of the propellers of one or more of propeller assemblies 116a-d. Similarly, in order to yaw left, the WIG <NUM> may increase the rotational speeds of the propellers of one or more of propeller assemblies 116a-d while decreasing the rotational speeds of the propellers of one or more of propeller assemblies 116e-h.

The main wing <NUM> may further include one or more aerodynamic control surfaces, such as flaps <NUM> and ailerons <NUM>, which may comprise movable hinged surfaces on the trailing or leading edges of the main wing <NUM> for changing the aerodynamic shape of the main wing <NUM>. The flaps <NUM> may be configured to extend downward below the main wing <NUM> in order to reduce stall speed and create additional lift at low airspeeds, while the ailerons <NUM> may be configured to extend upward above the main wing <NUM> in order to decrease lift on one side of the main wing <NUM> and induce a roll moment in the WIG <NUM>. In some examples, the ailerons <NUM> may be additionally configured to extend downward below the main wing <NUM> in a flaperon configuration to help the flaps <NUM> generate additional lift on the main wing <NUM>, which may be used to either create a rolling moment or additional balanced lift depending on coordinated movement of both ailerons. The flaps <NUM> and ailerons <NUM> may each include one or more actuators for raising and lowering the flaps <NUM> and ailerons <NUM>. The flaps <NUM> may include, for example, one or more of plain flaps, split flaps, slotted flaps, Fowler flaps, slotted Fowler flaps, Gouge flaps, Junkers flaps, or Zap flaps. Further, the flaps <NUM> (and the ailerons <NUM> when configured as flaperons) should be positioned so that they are in the wake of one or more of the propeller assemblies <NUM>. The ailerons <NUM> may be positioned so that they are in the wake of one or more of the propeller assemblies <NUM> in order to increase the effectiveness of the ailerons at low forward velocities. Some of the propeller assemblies <NUM> may be positioned so that no ailerons <NUM> are in their wake to increase thrust on the outboard wing during a turn without inducing adverse yaw. For example, in a left turn, a normal airplane would have adverse yaw to the right as the right aileron is deflected down, increasing drag. In the present disclosure, however, the right propeller assembly outboard of the right aileron may have its thrust increased relative to the respective left propeller assembly, initiating a turn without adverse yaw.

The tail <NUM> includes a vertical stabilizer <NUM>, a horizontal stabilizer <NUM>, and one or more control surfaces, such as elevators <NUM>. Similar to the flaps <NUM> and ailerons <NUM>, the elevators <NUM> may comprise movable hinged surfaces on the trailing or leading edges of the horizontal stabilizer <NUM> for changing the aerodynamic shape of the horizontal stabilizer <NUM> to control a pitch of the WIG <NUM>. The horizontal stabilizer <NUM> may be combined with the elevator <NUM>, creating a fully articulating horizontal stabilizer. Raising the elevators <NUM> above the hinge point creates a net downward force on the tail system and causes the WIG <NUM> to pitch upward. Lowering the elevators <NUM> below the hinge point creates a net upward force on the horizontal stabilizer <NUM> and causes the WIG <NUM> to pitch downward. The elevators <NUM> may include actuators, which may be operated by a control system of the WIG <NUM> in order to raise and lower the elevators <NUM>.

The tail <NUM> may further include a rudder <NUM>. The rudder <NUM> may comprise a movable hinged surface on the trailing edge of the vertical stabilizer <NUM> for changing the aerodynamic shape of the vertical stabilizer <NUM> to control the yaw of the WIG <NUM> when operating in an airborne mode. In some examples, the rudder <NUM> may additionally change a hydrodynamic shape of the hull <NUM> to control the yaw of the WIG <NUM> when operating in a waterborne mode. In order to facilitate such hydrodynamic control, the rudder <NUM> may be positioned low enough on the tail <NUM> that the rudder <NUM> is partially or entirely submerged when the hull <NUM> is floating in water. Namely, the rudder <NUM> may be positioned partially or entirely below a waterline of the hull <NUM>. The rudder <NUM> may include one or more actuators, which may be operated by a control system of the WIG <NUM> in order to rotate the hinged surface of the rudder <NUM> to the left or right of the vertical stabilizer <NUM>. Actuating the rudder <NUM> to the left (relative to the direction of travel) causes the WIG <NUM> to yaw left. Actuating the rudder <NUM> to the right (relative to the direction of travel) causes the WIG <NUM> to yaw right. As such, the rudder <NUM> may be used in combination with any of the other mechanisms disclosed herein for controlling the yaw of the WIG <NUM>, including in combination with the ailerons <NUM> during airborne operation and in combination with varying the rotational speeds of different ones of the propeller assemblies <NUM> to help improve maneuverability of the WIG <NUM> during waterborne operation.

While not shown in <FIG>, the WIG <NUM> may also include a distributed propulsion system on the tail <NUM>, which may be similar to the distributed propulsion system of propeller assemblies <NUM> on the main wing <NUM>. Such a distributed propulsion system may provide similar benefits of increasing the freestream velocity over the control surfaces (e.g., the elevators <NUM> and/or the rudder <NUM>) to allow for increased pitch and yaw control of the WIG <NUM> at lower travel speeds. When determining the number and size of propeller assemblies to include on the tail <NUM>, one may apply the same factors described above when determining the number and size of propeller assemblies to include on the main wing <NUM>.

As further shown in <FIG>, the WIG <NUM> includes one or more hydrofoil assemblies, such as the main hydrofoil assembly <NUM>, which is positioned closer to the middle or bow of the WIG <NUM>, and the rear hydrofoil assembly <NUM>, which is positioned closer to the stern of the WIG <NUM>. For instance, the main hydrofoil assembly <NUM> may be positioned between the bow and a midpoint (between the bow and stern) of the WIG <NUM>, and the rear hydrofoil assembly <NUM> may be positioned below the tail <NUM> of the WIG <NUM>. The main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> may help address a common challenge faced by waterborne WIGs, which is the process of breaking contact between the hull of the WIG and the water surface during takeoff. Prior to becoming airborne, WIGs experience a peak hydrodynamic drag, which is also known as the "hump drag. " This can be problematic for WIGs, as a large amount of power may be required to overcome this hump drag, which is required to further increase forward velocity and transition to airborne flight.

Previous design attempts for reducing the hump drag include both aerodynamic and hydrodynamic design approaches. As noted above in connection with the discussion of previous WIG designs having low aspect ratio wings, one example of an aerodynamic design approach is through the use of a power augmented ram (PAR), which uses forward-mounted propulsors to blow air under the wing, thereby creating a high-pressure zone under the WIG and lifting the WIG out of the water. These PAR designs are not well-suited for WIGs with high aspect ratio wings but instead are more effective with low aspect ratio wings very close to the water where the high pressure air can be better concentrated under the WIG. However, as noted above, low aspect ratio wings suffer significantly in aerodynamic efficiency and do not allow for a distributed blown-wing propulsion system.

Another example aerodynamic approach to reducing the hump drag is the use of catamaran hulls with textile skirts at the bow and stern to form an entrapped volume of air between the catamaran hulls. This volume of air can be inflated with high pressure air using the vehicle's aft propellers, allowing the vehicle to act as a quasi-hovercraft upon takeoff. However, this solution is less efficient than the PAR designs due to losses in the air tunnel, and presents additional challenges in the presence of waves on the water's surface.

Examples of hydrodynamic design approaches for reducing the hump drag include ski gear and fixed hydrofoils. Some WIGs have included ski gear, or deflecting planing tabs, to overcome the water suction and lift the WIG out of the water during takeoff. However, these designs have very high hydrodynamic drag, which may lead to reduced aerodynamic efficiency during flight. Other WIGs have included fixed hydrofoils that create an additional lift force while the WIG is waterborne in order to reduce the wetted surface area on the vehicle's hull at intermediate speeds prior to takeoff. However, because WIGs need to fly at very low altitudes when airborne, the fixed hydrofoils needed to be very short to avoid colliding with the water during flight. As a result, the fixed hydrofoils in these WIGs cannot lift the hull of the vehicle above the water waves during waterborne operation, which means the vehicles cannot (a) operate in high sea states or (b) operate at medium speeds (e.g., between the low speeds of a hull-borne operational mode and the high speeds of a wing-borne flight mode) in crowded harbors.

To improve upon and help address the issues of the previous WIG design described above, the main hydrofoil <NUM> and the rear hydrofoil <NUM> of the WIG <NUM> disclosed herein are configured to be retractable, large enough to lift the entire WIG out of the water and not impact the water surface, and to enable sustained operation in the hyrdrofoil-borne mode (where the entire weight of the craft is supported by the hydrofoil). The main hydrofoil assembly <NUM> may include a main foil <NUM>, one or more main foil struts <NUM> that couple the main foil <NUM> to the hull <NUM>, and one or more main foil control surfaces <NUM>. Similarly, the rear hydrofoil assembly <NUM> may include a rear foil <NUM>, one or more rear foil struts <NUM> that couple the rear foil <NUM> to the hull <NUM>, and one or more rear foil control surfaces <NUM>.

The main foil <NUM> and the rear foil <NUM> may each take the form of one or more hydrodynamic lifting surfaces (also referred to as "foils") designed to be operated submerged underwater while the hull <NUM> of the WIG <NUM> remains above and clear of the water's surface. In operation, as the WIG <NUM> moves through water with the main foil <NUM> and the rear foil <NUM> submerged, the foils generate a lifting force that causes the hull <NUM> to rise above the surface of the water. In order to cause the hull <NUM> to rise above the surface of the water, the lifting force generated by the foils must be at least equal to the weight of the WIG <NUM>. The lifting force of the foils depends on the speed and angle of attack at which the foils move through the water, as well as their various physical dimensions, including the aspect ratio, the surface area, the span, and the chord of the foils.

The height at which the hull <NUM> is elevated above the surface of the water during hydrofoil-borne operation is limited by the length of the one or more main foil struts <NUM> that couple the main foil <NUM> to the hull <NUM> and the length of the one or more rear foil struts <NUM> that couple the rear foil <NUM> to the hull <NUM>. In some examples, the main foil struts <NUM> and the rear foil struts <NUM> may be long enough to lift the hull <NUM> at least five feet above the surface of the water during hydrofoil-borne operation, which may allow for operation in substantially choppy waters. However, struts of other lengths may be used as well with the understanding that longer struts will allow for better wave-isolation of the hull <NUM> (but at the expense of stability of the WIG <NUM> and increasing complexity of the retraction system).

In practice, hydrofoils have a limited top speed before cavitation occurs, which results in vapor bubbles forming and imploding on the surface of the hydrofoil. Cavitation not only may cause damage to a hydrofoil, but also significantly reduces the amount of lift force generated by the hydrofoil and increases drag. Therefore, it is desirable to reduce the onset of cavitation by designing the main foil <NUM> and the rear foil <NUM> in a way that allows the foils to operate at higher speeds (e.g., ~<NUM>-<NUM>/h, ~<NUM>-<NUM> mph) and across the entire required hydrofoil-borne speed envelope before cavitation occurs. For instance, the onset of cavitation may be controlled based on the geometric design of the main foil <NUM> and the rear foil <NUM>. Additionally, the structural design of the main foil <NUM> and the rear foil <NUM> may allow the surfaces of the foils to flex and twist at higher speeds, which may reduce loading on the foils and delay the onset of cavitation.

Further, the distributed blown-wing propulsion system may help further delay the onset of cavitation on the main foil <NUM> and the rear foil <NUM>. Cavitation is caused by both (i) the amount of lift force generated by a hydrofoil and (ii) the profile of the hydrofoil (which is affected by both the hydrofoil's angle of attack and its vertical thickness) as it moves through water. Reducing the amount of lift force generated by the hydrofoil delays the onset of cavitation. Because the blown-wing propulsion system creates additional lift on the main wing <NUM>, the amount of lift force exerted on the main foil <NUM> and the rear foil <NUM> to lift the hull <NUM> out of the water is reduced. Further, because the main foil <NUM> and the rear foil <NUM> do not need to generate as much lift force to raise the hull <NUM> out of the water, their angles of attack may be reduced as well, which further reduces the onset of cavitation. By combining the blown-wing propulsion system with the hydrofoil designs described herein, the WIG <NUM> may operate in a hydrofoil-borne mode at speeds above <NUM> knots before cavitation occurs.

As shown in <FIG>, the main foil <NUM> may have a flattened V-shaped design in which a center portion of the main foil <NUM> is substantially flat and the ends of the main foil <NUM> extend upward toward the hull <NUM> of the WIG <NUM>. This flattened V-shape design may allow for passive regulation of the distance between the hull <NUM> and the surface of the water (also referred to as "ride height") while also allowing for passive roll-moment control. The passive regulation of ride height is achieved by having the tips of the V-shaped hydrofoil breach the surface of the water, reducing the lifting surface that is underwater. If the ride height is too low, the increased hydrofoil surface area under the surface of the water will create a net force greater than the weight of the WIG <NUM>, causing it to rise higher. If the ride height is too high, there will not be enough hydrofoil lifting area under the surface of the water, causing the WIG <NUM> to descend into the water. The passive roll stability is due to one side of the V-shaped hydrofoil breaching further out of the water than the other side. This creates a stabilizing roll moment when the WIG <NUM> is rolled to (for example) the left, because the left side of the V-shaped hydrofoil will have more surface under the water surface, allowing it to generate more lift than the right side.

As noted above, the main hydrofoil assembly <NUM> may include one or more main foil control surfaces <NUM>, and the rear hydrofoil assembly <NUM> may include one or more rear foil control surfaces <NUM>. The main foil control surfaces <NUM> may include one or more hinged surfaces on a trailing or leading edge of the main foil <NUM> as well as one or more actuators, which may be operated by a control system of the WIG <NUM> in order to rotate the hinged surfaces so that they extend above or below the main foil <NUM>. The main foil control surfaces <NUM> on the main foil <NUM> may be operated in a similar manner as the flaps <NUM> and ailerons <NUM> on the wing <NUM> of the WIG <NUM>. As one example, lowering the control surfaces <NUM> to extend below the main foil <NUM> may change a hydrodynamic shape of the main foil <NUM> in a manner that generates additional lift on the main foil <NUM>, similar to the aerodynamic effect of lowering the flaps <NUM>. As another example, asymmetrically raising one or more of the control surfaces <NUM> (e.g., raising a control surface <NUM> on only one side of the main foil <NUM>) may change a hydrodynamic shape of the main foil <NUM> in a manner that generates a roll force on the main foil <NUM>, similar to the aerodynamic effect of raising one of the ailerons <NUM>.

Likewise, the rear foil control surfaces <NUM> may include one or more hinged surfaces on a trailing or leading edge of the rear foil <NUM> as well as one or more actuators, which may be operated by a control system of the WIG <NUM> in order to rotate the hinged surfaces so that they extend above or below the rear foil <NUM>. The rear foil control surfaces <NUM> on the rear foil <NUM> may be operated in a similar manner as the elevators <NUM> on the tail <NUM> of the WIG <NUM>. As one example, lowering the control surfaces <NUM> to extend below the rear foil <NUM> may change a hydrodynamic shape of the rear foil <NUM> in a manner that causes the WIG <NUM> to pitch downwards, similar to the aerodynamic effect of lowering the elevators <NUM>. As another example, raising the control surfaces <NUM> to extend above the rear foil <NUM> may change a hydrodynamic shape of the rear foil <NUM> in a manner that causes the WIG <NUM> to pitch upwards, similar to the aerodynamic effect of raising the elevators <NUM>.

In some examples, one or both of the main foil control surfaces <NUM> or the rear foil control surfaces <NUM> may include rudder-like control surfaces similar to the rudder <NUM> on that tail <NUM> of the WIG <NUM>. For instance, the main foil control surfaces <NUM> may include one or more hinged surfaces on a trailing edge of the main foil strut <NUM> as well as one or more actuators, which may be operated by a control system of the WIG <NUM> in order to rotate the hinged surfaces so that they extend to the left or right of the main foil strut <NUM>. Similarly, the rear foil control surfaces <NUM> may include one or more hinged surfaces on a trailing edge of the rear foil strut <NUM> as well as one or more actuators, which may be operated by a control system of the WIG <NUM> in order to rotate the hinged surfaces so that they extend to the left or right of the rear foil strut <NUM>. Actuating the main foil control surfaces <NUM> or the rear foil control surfaces <NUM> in this manner may respectively change a hydrodynamic shape of the main foil strut <NUM> or the rear foil strut <NUM>, which may allow for controlling the yaw of the WIG <NUM> when operating in a waterborne or hyrdofoil-borne mode, similar to the effect of actuating the rudder <NUM> of the WIG <NUM> as described above.

In some examples, instead of (or in addition to) actuating hinged control surfaces on the main foil <NUM> and/or the rear foil <NUM>, a control system of the WIG <NUM> may actuate the entire main foil <NUM> and/or the entire rear foil <NUM> themselves. As one example, the WIG <NUM> may include one or more actuators for rotating the main foil <NUM> and/or the rear foil <NUM> around the yaw axis. As another example, the WIG <NUM> may include one or more actuators for controlling an angle of attack of the main foil <NUM> and/or the rear foil <NUM> (i.e., rotating the main foil <NUM> and/or the rear foil <NUM> around the pitch axis). As another example, the WIG <NUM> may include one or more actuators for rotating the main foil <NUM> and/or the rear foil <NUM> around the roll axis. As another example, the WIG <NUM> may include one or more actuators for changing a camber or shape of the main foil <NUM> and/or the rear foil <NUM>. As yet another example, the WIG <NUM> may include one or more actuators for flapping the main foil <NUM> and/or the rear foil <NUM> to help propel the WIG <NUM> forward or backwards. Other examples are possible as well.

Further, in some examples, the WIG <NUM> may dynamically control an extent to which the main foil <NUM> and/or the rear foil <NUM> are deployed based on an operational mode (e.g., hull-borne, hydrofoil-borne, or wing-borne modes) of the WIG <NUM>. For instance, during hull-borne mode, the rear foil <NUM> may be partially deployed or retracted to increase turning authority. The amount of partial deployment or retraction may be a function of the desired overall vehicle draft when operating in a shallow water environment. During hydrofoil-borne mode, the main hydrofoil <NUM> may be partially retracted in order to reduce the distance between the hull of the vehicle and the water's surface. This may increase the amount of lift generated by the main wing <NUM> by operating the wing closer to the surface of the water, increasing the effects of aerodynamic ground effect.

As noted above, one or both of the main hydrofoil assembly <NUM> or the rear hydrofoil assembly <NUM> may interface with a deployment system that allows for retracting the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> into or toward the hull <NUM> for hull-borne or wing-borne operation and extending the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> below the hull <NUM> for hydrofoil-borne operation.

<FIG> depicts an example main hydrofoil deployment system <NUM> that allows for retracting and extending the main hydrofoil assembly <NUM>. As shown, the main hydrofoil deployment system <NUM> may take the form of a linear actuator that includes one or more brackets <NUM> coupling the main hydrofoil assembly <NUM> (by way of the main foil struts <NUM>) to one or more vertical tracks <NUM>. The brackets <NUM> may be configured to move vertically along the tracks <NUM>, such that when the brackets <NUM> move vertically along the tracks <NUM>, the main hydrofoil assembly <NUM> likewise moves vertically. The brackets <NUM> may be coupled to a leadscrew <NUM> that, when rotated, causes vertical movement of the brackets <NUM>. The leadscrew <NUM> may be rotated by any of various sources of torque, such as an electric motor coupled to the leadscrew <NUM> by a gearbox <NUM>.

The main hydrofoil deployment system <NUM> may further include one or more sensors <NUM> configured to detect a vertical position of the main hydrofoil assembly <NUM>. As shown, the sensors <NUM> include a first sensor 310a that senses when the main hydrofoil assembly <NUM> has reached a fully retracted position and a second sensor 310b that senses when the main hydrofoil assembly <NUM> has reached a fully extended position. However, the main hydrofoil deployment system <NUM> may include additional sensors for detecting additional discrete positions or continuous positions of the main hydrofoil assembly <NUM>. The sensors <NUM> may be included as part of, or otherwise configured to communicate with, the control system of the WIG <NUM> to provide the control system with data indicating the position of the main hydrofoil assembly <NUM>. The control system may then use the data from the sensors <NUM> to determine whether to operate the electric motor to retract or extend the main hydrofoil assembly <NUM>.

In some examples, such as examples where the linear actuator is not a self-locking linear actuator, the main foil deployment system <NUM> may include a locking or braking mechanism for holding the main foil struts <NUM> in a fixed position (e.g., in a fully retracted or fully extended position). The locking mechanism may be, for example, a dual-action mechanical brake coupled to the electric motor, the leadscrew <NUM>, or the gearbox <NUM>.

While the above description provides various details of an example main foil deployment system <NUM>, it should be understood that the main foil deployment system <NUM> depicted in <FIG> is for illustrative purposes and is not meant to be limiting. For instance, the main foil deployment system <NUM> may include any of various linear actuators now known or later developed that are capable of retracting and extending the main hydrofoil assembly <NUM>.

<FIG> and <FIG> depict an example rear foil deployment system <NUM> that allows for retracting and extending the rear foil <NUM>. As shown, the rear foil deployment system <NUM> may include a pulley system <NUM> that couples an actuator <NUM> to the rear foil strut <NUM>. When actuated, the actuator <NUM> causes the pulley system <NUM> to raise or lower the rear foil strut <NUM> by causing the rear foil strut <NUM> to slide vertically along a shaft <NUM>. While not depicted in <FIG> and <FIG>, the rudder <NUM> may also be mounted to the shaft <NUM> such that, when the actuator <NUM> raises the rear foil strut <NUM>, the rear foil strut <NUM> retracts at least partially into the rudder <NUM>. Additionally, the rear foil deployment system <NUM> may include one or more servo motors for rotating the rear foil strut <NUM> around the shaft. In this respect, the rear foil strut <NUM> may be rotated around the shaft to act as a hydro-rudder when submerged in water or to act as an aero-rudder when out of the water. Further, because the rudder <NUM> is mounted to the same shaft <NUM> as the rear foil strut <NUM> and the rear foil strut <NUM> can be retracted into the rudder <NUM>, the same servo motor can also be used to control rotation of the rudder <NUM>.

The actuator <NUM> of the rear foil deployment system <NUM> may take various forms and may, for instance, include any of various linear actuators now known or later developed that are capable of retracting and extending the rear hydrofoil assembly <NUM>. Further, in some examples, the actuator <NUM> may have a non-unitary actuation ratio such that a given movement of the actuator <NUM> causes a larger corresponding induced movement of the rear hydrofoil assembly <NUM>. This can help allow for faster retractions of the rear hydrofoil assembly <NUM>, which may be beneficial during takeoff, as described in further detail below.

The main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may be designed such that, when fully retracted, the hydrofoil assembly is flush, conformal, or tangent to the hull <NUM>. For instance, in some examples, the hull <NUM> may include one or more recesses configured to receive the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM>, and the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may be shaped such that when the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> are fully retracted into the one or more recesses of the hull <NUM>, the outer contour of the hull <NUM> forms a substantially smooth transition at the intersection of the hull <NUM> and the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM>.

In other examples, the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may not conform to the shape of the hull <NUM> when fully retracted but instead may protrude slightly below the hull <NUM>. In these examples, the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may have a non-negligible effect on the aerodynamics of the WIG <NUM>, and the WIG <NUM> may be configured to leverage these effects to provide additional control of the WIG <NUM>. For instance, when the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> are retracted but still exposed, the exposed hydrofoil may be manipulated in flight to impart forces and moments on the WIG <NUM> similar to an aero-control surface. Traditional hydrofoils have control surfaces (such as flaps attached at the rear) that are sized to displace water and would not be effective in much-lighter-than-water air. One or both of the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> of the WIG <NUM> disclosed herein, however, may be mounted on a pivot which is locked underwater but may be unlocked to allow the hydrofoil to move around the pivot in the air. At that point, the control surfaces act like trim tabs and are able to effect movement of the entire unlocked, pivoting hydrofoil which would otherwise impractically large and heavy servo motors. An additional benefit of this design is that the hydrofoil may be unlocked and moved through a slow servo and/or a combination of control surface movement combined with forward movement through water, and then re-locked such that the hydrofoil is at a selected angle of incidence.

Because the main hydrofoil assembly <NUM> is configured to be retractable, the hull <NUM> may include openings through which the struts <NUM> of the main hydrofoil assembly <NUM> may be retracted and extended. However, when the hull <NUM> contacts the water surface, water may seep into the hull <NUM> through these openings. To account for this, the hull <NUM> may be designed to isolate any water that enters the hull <NUM> and allow for the water to drain from the hull <NUM> when the hull <NUM> is lifted out of the water. For instance, the hull <NUM> may include pockets <NUM> on each side of the hull <NUM> aligned above the struts <NUM>. The pockets <NUM> may be isolated from the remainder of the interior of the hull <NUM> so that when water accumulates in the pockets <NUM>, the water does not reach any undesired areas, like the cockpit, passenger seating area, or any areas that house the battery system <NUM> or components of the control system of the WIG <NUM>. Further, the pockets <NUM> may include venting holes or other openings located at or near the bottom of the pockets <NUM>. While such venting openings may allow water to enter the pockets <NUM>, they may likewise allow any accumulated water to vent out of the pockets <NUM> when the hull <NUM> is lifted out of the water.

While not shown in the figures, the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may further include one or more propellers for additional propulsion when submerged underwater. For instance, one or more propellers may be mounted to the main foil <NUM> and/or the rear foil <NUM>. Such propellers may provide additional propulsion force to the WIG <NUM> during hydrofoil-borne or hull-borne operation. In some examples, the one or more propellers may additionally or alternatively be mounted to the hull <NUM> such that the propellers are submerged during hull-borne operation and may be used to provide additional propulsion force to the WIG <NUM> during hull-borne operation.

The main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may further include various failsafe mechanisms in case of malfunction. For instance, if the main hydrofoil deployment system <NUM> or the rear hydrofoil deployment system <NUM> malfunctions and cannot retract the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM>, then the WIG <NUM> may be configured to jettison the assembly that is unable to be retracted. The main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may be coupled to the hull <NUM> by a releasable latch. The control system of the WIG <NUM> may identify a retraction malfunction, for instance based on data received from the positional sensors <NUM>, and the control system may responsively open the latch to release the connection between the hull <NUM> and the malfunctioning hydrofoil assembly. In some examples, the weight of the malfunctioning hydrofoil assembly may provide sufficient force to jettison the malfunctioning hydrofoil assembly out of the hull <NUM> when the latch is opened, or the WIG <NUM> may include an actuator or some other mechanism to jettison the malfunctioning hydrofoil assembly out of the hull <NUM>. In other examples, instead of jettisoning a malfunctioning hydrofoil assembly, the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> may be designed to break in a controlled manner upon impact with a water surface. For instance, a joint between the main foil struts <NUM> and the hull <NUM> and/or a joint between the rear foil struts <NUM> and the hull <NUM> may be configured to disconnect when subjected to a torque significantly larger than standard operational torques at the joints. Other designs for providing controlled breaks are possible as well.

<FIG> depicts a simplified block diagram illustrating various components that may be included in an example control system <NUM> of the WIG <NUM>. The components of the control system <NUM> may include one or more processors <NUM>, data storage <NUM>, a communication interface <NUM>, a propulsion system <NUM>, actuators <NUM>, a Global Navigation Satellite System (GNSS) <NUM>, an inertial navigation system (INS) <NUM>, a radar system <NUM>, a lidar system <NUM>, an imaging system <NUM>, various sensors <NUM>, a flight instrument system <NUM>, and control effectors <NUM>, some or all of which may be communicatively linked by one or more communication links <NUM> that may take the form of a system bus, a communication network such as a public, private, or hybrid cloud, or some other connection mechanism.

The one or more processors <NUM> may comprise one or more processing components, such as general-purpose processors (e.g., a single- or multi-core microprocessor), special-purpose processors (e.g., an application-specific integrated circuit or digital-signal processor), programmable logic devices (e.g., a field programmable gate array), controllers (e.g., microcontrollers), and/or any other processor components now known or later developed. Further, while the one or more processors <NUM> are depicted as a separate stand-alone component of the control system <NUM>, it should also be understood that the one or more processors <NUM> could comprise processing components that are distributed across one or more of the other components of the control system <NUM>.

The data storage <NUM> comprises one or more non-transitory computer-readable storage mediums that are collectively configured to store (i) program instructions that are executable by the one or more processors <NUM> such that the control system <NUM> is configured to perform some or all of the functions disclosed herein, and (ii) data that may be received, derived, or otherwise stored, for example, in one or more databases, file systems, or the like, by the control system <NUM> in connection with the functions disclosed herein. In this respect, the one or more non-transitory computer-readable storage mediums of data storage <NUM> may take various forms, examples of which may include volatile storage mediums such as random-access memory, registers, cache, etc. and non-volatile storage mediums such as read-only memory, a hard-disk drive, a solid-state drive, flash memory, an optical-storage device, etc. Further, while the data storage <NUM> is depicted as a separate stand-alone component of the control system <NUM>, it should also be understood that the data storage <NUM> may comprise computer-readable storage mediums that are distributed across one or more of the other components of the control system <NUM>.

The communication interface <NUM> may include one or more wireless interfaces and/or one or more wireline interfaces, which allow the control system <NUM> to communicate via one or more networks. Example wireless interfaces may provide for communication under one or more wireless communication protocols, such as Bluetooth, WiFi (e.g., an IEEE <NUM> protocol), Long-Term Evolution (LTE), WiMAX (e.g., an IEEE <NUM> standard), a radiofrequency ID (RFID) protocol, near-field communication (NFC), and/or other wireless communication protocols. Example wireline interfaces may include an Ethernet interface, a Universal Serial Bus (USB) interface, CAN Bus, RS-<NUM>, or similar interface to communicate via a wire, a twisted pair of wires, a coaxial cable, an optical link, a fiber-optic link, or other physical connection to a wireline network.

The propulsion system <NUM> may include one or more electronic speed controllers (ESCs) for controlling the electric motor propeller assemblies <NUM> distributed across the main wing <NUM> and, in some examples, across the horizontal stabilizer <NUM>. In some examples, the propulsion system <NUM> may include a separate ESC for each respective propeller assembly <NUM>, such that the control system <NUM> may individually control the rotational speeds of the electric motor propeller assemblies <NUM>.

The actuators <NUM> may include any of the actuators described herein, including (i) actuators for raising and lowering the flaps <NUM>, ailerons <NUM>, elevators <NUM>, main foil control surfaces <NUM>, and rear foil control surfaces <NUM>, (ii) actuators for turning the rudder <NUM>, the main foil control surfaces <NUM> positioned on the main foil struts <NUM>, and the rear foil control surfaces <NUM> positioned on the rear foil strut <NUM>, (iii) actuators for retracting and extending the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM>, and/or (iv) actuators for performing the various other disclosed actuations of the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM>. Each of the actuators described herein may include any actuators now known or later developed capable of performing the disclosed actuation. Examples of different types of actuators may include linear actuators, rotary actuators, hydraulic actuators, pneumatic actuators, electric actuators, electro-hydraulic actuators, and mechanical actuators. Further, more specific examples of actuators may include electric motors, stepper motors, and hydraulic cylinders. Other examples are contemplated herein as well.

The GNSS system <NUM> may be configured to provide measurement of the location, speed, altitude, and heading of the WIG <NUM>. The GNSS system <NUM> includes one or more radio antennas paired with signal processing equipment. Data from the GNSS system <NUM> may allow the control system <NUM> to estimate the position and velocity of the WIG <NUM> in a global reference frame, which can be used for route planning, operational envelope protection, and vehicle traffic deconfliction by both understanding where the WIG <NUM> is located and comparing the location with known traffic.

The INS <NUM> may include various sensors that are configured to provide data that is typical of well-known INS systems. For example, the INS <NUM> may include motion sensors, such as angular and/or linear accelerometers, and rotational sensors, such as gyroscopes, to calculate the position, orientation, and velocity of the WIG <NUM> using dead reckoning techniques. One or more INS systems may be used by the control system to calculate actuator outputs to stabilize or otherwise control the vehicle during all modes of operation.

The radar system <NUM> may be configured to provide data that is typical of well-known radar systems. For example, the radar system <NUM> may include a transmitter and a receiver. The transmitter may transmit radio waves via a transmitting antenna. The radio waves reflect off an object and return to the receiver. The receiver receives the reflected radio waves via a receiving antenna, which may be the same antenna as the transmitting antenna, and the radar system <NUM> processes the received radio waves to determine information about the object's location and speed relative to the WIG <NUM>. This radar system <NUM> may be utilized to detect, for example, the water surface, maritime or airborne vehicle traffic, wildlife, or weather.

The lidar system <NUM> may be configured to provide data that is typical of well-known lidar systems. For example, the lidar system <NUM> may include a light source and an optical receiver. The light source emits a laser that reflects off an object and returns to the optical receiver. The lidar system <NUM> measures the time for the reflected light to return to the receiver to determine a distance between the WIG <NUM> and the object. This lidar system <NUM> may be utilized by the flight control system to measure the distance from the WIG <NUM> to the surface of the water in various spatial measurements.

The imaging system <NUM> may include one or more still and/or video cameras configured to capture image data from the environment of the WIG <NUM>. In some examples, the cameras may include charge-coupled device (CCD) cameras, complementary metal-oxide-semiconductor (CMOS) cameras, short-wave infrared (SWIR) cameras, mid-wave infrared (MWIR) cameras, or long-wave infrared (LWIR) cameras. The imaging system <NUM> may provide any of various possible applications, such as obstacle avoidance, localization techniques, water surface tracking for more accurate navigation (e.g., by applying optical flow techniques to images), video feedback, and/or image recognition and processing, among other possibilities.

As noted above, the control system <NUM> may further include various other sensors <NUM> for use in controlling the WIG <NUM>. In line with the discussion above, examples of such sensors <NUM> may include thermal sensors or other fire detection sensors for detecting a fire in the hull <NUM> or for detecting thermal runaway in the battery system <NUM>. As further described above, the sensors <NUM> may include position sensors for sensing a position of the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> (e.g., sensing whether the assemblies are in a retracted or extended position). Examples of position sensors may include photodiode sensors, capacitive displacement sensors, eddy-current sensors, Hall effect sensors, inductive sensors, or any other position sensors now known or later developed.

In some examples, the sensors <NUM> may include any of various altimeter sensors. As one example, the sensors <NUM> may include an ultrasonic altimeter configured to emit and receive ultrasonic waves. The emitted ultrasonic waves reflect off the water surface below the WIG <NUM> and return to the altimeter. The ultrasonic altimeter measures the time for the reflected ultrasonic wave to return to the altimeter to determine a distance between the WIG <NUM> and the water surface. As another example, the sensor <NUM> may include a barometer for use as a pressure altimeter. The barometer measures the atmospheric pressure in the environment of the WIG <NUM> and determines the altitude of the WIG <NUM> based on the measured pressure. As another example, the sensor <NUM> may include a radar altimeter to emit and receive radio waves. The radar altimeter measures the time for the radio wave to reflect off of the surface of the water below the WIG <NUM> to determine a distance between the WIG <NUM> and the water surface. These various sensors may be placed on different locations on the WIG <NUM> in order to reduce the impact of sensor constraints, such as sensor deadband or sensitivity to splashing water.

Further, the control system <NUM> may be configured to use various ones of the sensors <NUM> or other components of the control system <NUM> to help navigate the WIG <NUM> through maritime traffic or to avoid any other type of obstacle. For example, the control system <NUM> may determine a position, orientation, and velocity of the WIG <NUM> based on data from the INS <NUM> and/or the GNSS <NUM>, and the control system <NUM> may determine the location of an obstacle, such as a maritime vessel, a dock, or various other obstacles, based on data from the radar system <NUM>, the lidar system <NUM>, and/or the imaging system <NUM>. In some examples, the control system <NUM> may determine the location of an obstacle using the Automatic Identification System (AIS). In any case, based on the determined position, orientation, and velocity of the WIG <NUM> and the determined location of the obstacle, the control system <NUM> may maneuver the WIG <NUM> to avoid collision with the obstacle by actuating various control surfaces of the WIG <NUM> in any of the manners described herein.

The flight instrument system <NUM> may include various instruments for providing a pilot of the WIG <NUM> with data about the flight situation of the WIG <NUM>. Example instruments may include instruments for providing data about the altitude, velocity, heading, orientation (e.g., yaw, pitch, and roll), battery levels, or any other information provided by the various other components of the control system <NUM>.

The control effectors <NUM> may include various input devices that may allow an operator to interact with and input signals to the control system <NUM>. Example control effectors <NUM> may include one or more joysticks, thrust control levers, buttons, switches, dials, levers, or touch screen displays, to name a few. In operation, a pilot may use the control effectors <NUM> to operate one or more control surfaces of the WIG <NUM>. For instance, as one example, when the pilot moves the joystick in a particular direction, the control system <NUM> may actuate one or more control surfaces of the WIG <NUM> to cause the WIG <NUM> to move in the direction corresponding to the joystick movement. As another example, when the pilot actuates (or increases actuation of) the throttle, the control system <NUM> may cause a propulsion control surface of the WIG <NUM> (e.g., the propeller assemblies <NUM>) to increase the propulsion force exerted on the WIG <NUM>, and when the pilot reduces actuation of the throttle, the control system <NUM> may cause a propulsion control surface of the WIG <NUM> to decrease the propulsion force exerted on the WIG <NUM>. Other examples of control effectors <NUM> may be implemented for actuating various control surfaces of the WIG <NUM> as well.

The control surfaces on the WIG <NUM> may be utilized by the control system <NUM> in different modes of operation. The amount of deflection of each control surface may be calculated by the control system <NUM> based on a number of input variables, including but not limited to vehicle position, velocity, attitude, acceleration, rotational rates, and/or altitude above water. Table <NUM> below identifies, for each control surface of the WIG <NUM>, example operational modes in which the control surface may be used to control movement of the WIG <NUM>. In the tables below, the propulsion control surfaces may include the propeller assembly <NUM> as well as any propellers mounted to the hull <NUM>, main hydrofoil assembly <NUM>, or rear hydrofoil assembly <NUM>. The aerodynamic elevator control surfaces may include elevator <NUM>, the aerodynamic ailerons may include ailerons <NUM>, the aerodynamic rudder may include rudder <NUM> (when not submerged), the aerodynamic flaps may include flaps <NUM>, the hydrodynamic elevator may include rear foil control surfaces <NUM>, the hydrodynamic flaps may include main foil control surfaces <NUM>, and the hydrodynamic rudder may include rudder <NUM> (when submerged).

When actuating the control surfaces in the various example operational modes identified in Table <NUM> above, the control system <NUM> may execute different levels of stabilization along the various vehicle axes during different modes of operation. Table <NUM> below identifies example stabilization controls that the control system <NUM> may apply during the various modes of operation for each axis of the WIG <NUM>. Closed loop control may comprise feedback and/or feed forward control.

Further, the control system <NUM> may be configured to actuate different control surfaces to control movement of the WIG <NUM> about its different axes. Table <NUM> below identifies example axial motions that are affected by the various control surfaces of the WIG <NUM>.

<FIG> depicts various example modes of operation of the WIG <NUM>, separated into six numbered stages, each of which are described in further detail below.

At stage one, the WIG <NUM> is docked and floating on the hull <NUM> (i.e., in a hull-borne mode) with the buoyancy of the outriggers <NUM> providing for roll stabilization of the WIG <NUM>. While docked, the battery system <NUM> of the WIG <NUM> may be charged. Rapid charging may be aided with water-based cooling systems, which may be open- or closed-loop systems. The surrounding body of water may be used in the loop or as a heat sink. In some examples, the WIG <NUM> may include a heat sink integrated into the hull <NUM> for exchanging heat from the battery system <NUM> to the surrounding body of water. In other examples, the heat sink may be located offboard in order to reduce the mass of the WIG <NUM>.

Additionally, while the WIG <NUM> is docked, the propeller assemblies <NUM> may be folded in a direction away from the dock to help avoid collision with nearby structures or people. This folding may be actuated in various ways, such as by metal spring force, hydraulic pressure, electromechanical actuation, or centrifugal force due to propeller rotation. Other examples are possible as well. Further, the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> may be retracted (or partially retracted) to avoid collisions with nearby underwater structures.

Once any passengers or cargo have been loaded onto the WIG <NUM> and the WIG <NUM> is ready to depart, the WIG <NUM> can use its propulsion systems, including the propeller assemblies <NUM> and/or the underwater propulsion system (e.g., one or more propellers mounted to the hull <NUM>, the main foil <NUM>, and/or the rear foil <NUM>), to maneuver away from the dock while remaining hull-borne. In some examples, the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> may remain retracted (or partially retracted) during this maneuvering to reduce the risk of hitting underwater obstacles near docks or in shallow waterways. However, when there is limited risk of hitting underwater obstacles, the WIG <NUM> may partially or fully extend the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM>. With the main hydrofoil assembly <NUM> and/or the rear hydrofoil assembly <NUM> extended, the WIG <NUM> may actuate the main foil control surfaces <NUM> and/or the rear foil control surfaces <NUM> to improve maneuverability as described above.

At low speeds during hull-borne operation, the control system <NUM> may control a position and/or rotation of the WIG <NUM> by causing all of the propeller assemblies <NUM> to spin at the same idle speed, but with a first subset spinning in a forward direction and a second subset spinning in a reverse direction. For example, the control system <NUM> may cause propeller assemblies 116a, 116c, 116f, and <NUM> to idle in reverse and propeller assemblies 116b, 116d, 116e, and <NUM> to idle forward. In this arrangement, the control system <NUM> may cause the WIG <NUM> to make various maneuvers without having to change the direction of rotation of any of the propeller assemblies <NUM>. For instance, in order to induce a yaw on the WIG <NUM>, the control system <NUM> may increase the speed of the reverse propeller assemblies on one side of the wing <NUM> while increasing the speed of the forward propeller assemblies on the other side of the wing <NUM> and without causing any of the propeller assemblies to transition from forward to reverse or from reverse to forward. For example, idling the propellers at a nominal RPM may allow for faster response in generating a yaw moment on the WIG <NUM>, because the propellers required for generating the yaw moment do not have to increase from zero RPM to the desired RPM value, they can spin from the idle RPM to the desired RPM value.

In order to transition to stage two, the WIG <NUM> can fully extend the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> (if not already extended) and accelerate using the propulsion system as previously described. The WIG <NUM> accelerates to a speed at which the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> alone support the weight of the WIG <NUM>, and the hull <NUM> is lifted above the surface of the water and clear of any surface waves (e.g., example embodiments may support a maximum wave height of ~<NUM>-<NUM>, ~<NUM>-<NUM> ft).

While transitioning to this hydrofoil-borne mode, the control system <NUM> may actuate the main foil control surfaces <NUM> and/or the rear foil control surfaces <NUM> and/or the propulsion system to stabilize the attitude of the WIG <NUM> in order to maintain the desired height above the surface of the water, vehicle heading, and vehicle forward velocity. For instance, the control system <NUM> may detect various changes in the yaw, pitch, or roll of the WIG <NUM> based on data provided by the INS <NUM>, and the control system <NUM> may make calculated actuations of the main foil control surfaces <NUM> and/or the rear foil control surfaces <NUM> to counteract the detected changes.

Once the WIG <NUM> has fully transitioned to hydrofoil-borne operation and the hull <NUM> leaves the surface of the water, the drag forces exerted on the WIG <NUM> drop significantly due to the hull <NUM> no longer contributing to the water-based drag. As such, the control system <NUM> may reduce the speeds of the propeller assemblies <NUM> to lower the thrust of the WIG <NUM>. The control system <NUM> can sustain this operational mode by actively controlling the pitch and speed of the WIG <NUM> so that the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM> continue to entirely support the weight of the WIG <NUM>.

In order to transition to wing-borne operation in stage three, the control system <NUM> may accelerate the WIG <NUM> by increasing the speeds of the propeller assemblies <NUM>. The control system <NUM> may accelerate the WIG <NUM> to a desired takeoff speed. Because the WIG <NUM> is operating in a hydrofoil-borne mode at this point, the desired takeoff speed must be below the hydrofoil cavitation speed and is therefore significantly limited. In some examples, the desired takeoff speed is approximately <NUM> knots. However, as described above, by arranging the propeller assemblies <NUM> in a blown-wing configuration, the WIG <NUM> may generate additional lift that allows for takeoff at such low speeds.

Once the control system <NUM> determines that the WIG <NUM> has reached the desired takeoff speed, the control system <NUM> may deploy the flaps <NUM> (and the ailerons <NUM> if configured as flaperons), causing the wing <NUM> to generate additional lift. The control system <NUM> additionally actuates the rear foil control surfaces <NUM> and/or the elevators <NUM> in order to pitch the WIG <NUM> upward and increase the angle of attack of the wing <NUM> and the hydrofoil assemblies <NUM>, <NUM>. In this configuration, the wing <NUM> and hydrofoil assemblies <NUM>, <NUM> create enough lift force to accelerate the WIG <NUM> upwards until the hydrofoil assemblies <NUM>, <NUM> breach the surface of the water and the entire weight of the WIG <NUM> is supported by the lift of the wing <NUM>.

In some examples, when performing this transition from hydrofoil-borne operation to wing-borne operation, the control system <NUM> may quickly deploy the flaps <NUM> (and the ailerons <NUM> if configured as flaperons) over a very short period of time (e.g., in less than <NUM> second, less than <NUM> seconds, or less than <NUM> seconds). Quickly deploying the flaps <NUM> (and ailerons <NUM>) in this manner creates even further additional lift forces on the wing <NUM> that may help "pop" the WIG <NUM> out of the water and into wing-borne operation.

Additionally, during the transition from hydrofoil-borne operation to wing-borne operation, the control system <NUM> may actuate various control surfaces of the WIG <NUM> to balance moments along the pitch axis. For instance, the propeller assemblies <NUM>, the flaps <NUM>, and the drag from the hydrofoil assemblies <NUM>, <NUM> all generate nose-down moments around the center of gravity about the pitch axis during transition. To counteract these forces, the control system <NUM> may deploy the elevator <NUM> and the rear foil control surfaces <NUM> to generate a nose-up moment and stabilize the WIG <NUM>.

Once the transition from hydrofoil-borne operation to wing-borne operation is complete at stage three, the control system <NUM> may cause the main hydrofoil deployment system <NUM> and the rear hydrofoil deployment system <NUM> to respectively retract the main hydrofoil assembly <NUM> and the rear hydrofoil assembly <NUM>. In practice, the control system <NUM> may initiate this retraction as soon as the hydrofoil assemblies <NUM>, <NUM> are clear of the water in order to reduce the chance of the hydrofoil assemblies <NUM>, <NUM> reentering the water. The control system <NUM> may determine that the hydrofoil assemblies <NUM>, <NUM> are clear of the water in various ways. As one example, the control system <NUM> may make such a determination based on a measured altitude of the WIG <NUM> (e.g., based on data provided by the radar system <NUM>, the lidar system <NUM>, or the other sensors <NUM> described above for measuring an altitude of the WIG <NUM>). As another example, the sensors <NUM> may further include one or more conductivity sensors, temperature sensors, pressure sensors, strain gauge sensors, or load cell sensors arranged on the hydrofoil assemblies <NUM>, <NUM>, and the control system <NUM> may determine that the hydrofoil assemblies <NUM>, <NUM> are clear of the water based on data from these sensors.

Once the WIG <NUM> is clear of the water, the control system <NUM> can continue to accelerate the WIG <NUM> to a desired cruise velocity by controlling the speed of the propeller systems <NUM>. The control system <NUM> may retract the flap systems when the WIG <NUM> has achieved sufficient airspeed to generate enough lift to sustain altitude without them. Additionally, the control system <NUM> can actuate the various control surfaces of the WIG <NUM> and/or apply differential thrust to the propeller systems <NUM> to perform any desired maneuvers, such as turning, climbing, or descending, and to provide efficient lift distribution. While in wing-borne mode, the WIG <NUM> can fly both low over the water's surface in ground-effect, or above ground-effect depending on operational conditions and considerations.

In order to transition to stage four, the control system <NUM> determines that the hydrofoil assemblies <NUM>, <NUM> are fully retracted so that the WIG <NUM> may safely land on its hull <NUM>. The control system <NUM> may additionally determine and suggest a desired landing direction and/or location based on observed, estimated, or expected water surface conditions (e.g., based on data from the radar system <NUM>, the lidar system <NUM>, the imaging system <NUM>, or other sensors <NUM>).

The control system <NUM> initiates deceleration of the WIG <NUM>, for instance by reducing the speeds of the propeller systems <NUM>, until the WIG <NUM> reaches a desired landing airspeed. During the deceleration, the control system <NUM> may deploy the flaps <NUM> to increase lift at low airspeeds and/or to reduce the stall speed. Once the WIG <NUM> reaches the desired landing airspeed (e.g., approximately <NUM> knots), the control system <NUM> reduces the descent rate (e.g., to be less than approximately <NUM>/s, <NUM> ft/min). As the WIG <NUM> approaches the surface of the water (e.g., once the control system <NUM> determines that the WIG <NUM> is within <NUM> (<NUM> feet) of the water surface), the control system <NUM> further slows the descent rate to cushion the landing (e.g., to be less than approximately <NUM>/s, <NUM> ft/min). As the hull <NUM> of the WIG <NUM> impacts the surface of the water, the control system <NUM> reduces thrust, and the WIG <NUM> rapidly decelerates due to the presence of hydrodynamic drag, the reduction in forward thrust, and the reduction or elimination of blowing air over the wing which significantly reduces lift causing the vehicle to settle into the water. The hull <NUM> settles into the water as the speed is further reduced until the WIG <NUM> is stationary.

Once the WIG <NUM> is settled in the water, the WIG <NUM> may transition to stage five by extending the hydrofoil assemblies <NUM>, <NUM> in order to transition from hull-borne operation to hydrofoil-borne operation in the same manner as described above. The control system <NUM> may then sustain the hydrofoil-borne mode at stage five and maneuver the WIG <NUM> into port while keeping the hull <NUM> insulated from surface waves. The WIG <NUM> may then transition to back to hull-borne operation in stage six when the control system <NUM> reduces the thrust generated by the propeller assemblies <NUM> to lower the speed of the WIG <NUM> until the hull <NUM> settles into the water. The control system <NUM> may then retract the hydrofoil assemblies <NUM>, <NUM> and engage in hull-borne operation as described above to maneuver the WIG <NUM> into a dock for disembarking passengers or goods and recharging the battery system <NUM>.

Claim 1:
A wing-in-ground effect vehicle (<NUM>) comprising:
a main wing (<NUM>) comprising one or more main wing control surfaces (<NUM>, <NUM>);
a tail (<NUM>) comprising one or more tail control surfaces (<NUM>); and
a retractable hydrofoil system (<NUM>, <NUM>) comprising a retractable hydrofoil, wherein the retractable hydrofoil system is configured to operate in: (i) an extended configuration in which the retractable hydrofoil extends below a hull (<NUM>) of the wing-in-ground effect vehicle for submersion below a water surface and (ii) a retracted configuration in which the retractable hydrofoil is retracted at least partially into the hull of the wing-in-ground effect vehicle;
characterised by further comprising:
a blown-wing propulsion system (<NUM>) comprising an array of electric motors arranged along at least one of the main wing or the tail; and
a control system (<NUM>) configured to (i) determine a position, orientation, and velocity of the wing-in-ground effect vehicle and (ii) maneuver the wing-in-ground effect vehicle based on the determined position, orientation, and velocity, wherein maneuvering the wing-in-ground effect vehicle comprises (i) causing one or more actuators of the retractable hydrofoil system to change an orientation of the retractable hydrofoil when the retractable hydrofoil system is operating in the extended configuration, (ii) causing one or more actuators of the main wing and the tail to change an orientation of the main wing control surfaces (<NUM>, <NUM>) and tail control surfaces (<NUM>) when the retractable hydrofoil system is operating in the retracted configuration and (iii) causing one or more of the electric motors of the blown-wing propulsion system to change speed.