Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C9/00—Adjustable control surfaces or members, e.g. rudders
  • B64C9/38—Jet flaps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60V—AIR-CUSHION VEHICLES
  • B60V1/00—Air-cushion
  • B60V1/08—Air-cushion wherein the cushion is created during forward movement of the vehicle by ram effect
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60V—AIR-CUSHION VEHICLES
  • B60V1/00—Air-cushion
  • B60V1/11—Stability or attitude control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60V—AIR-CUSHION VEHICLES
  • B60V1/00—Air-cushion
  • B60V1/14—Propulsion; Control thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60V—AIR-CUSHION VEHICLES
  • B60V1/00—Air-cushion
  • B60V1/22—Air-cushion provided with hydrofoils
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C35/00—Flying-boats; Seaplanes
  • B64C35/001—Flying-boats; Seaplanes with means for increasing stability on the water
  • B64C35/003—Flying-boats; Seaplanes with means for increasing stability on the water using auxiliary floats at the wing tips
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C35/00—Flying-boats; Seaplanes
  • B64C35/006—Flying-boats; Seaplanes with lift generating devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D27/00—Arrangement or mounting of power plants in aircraft; Aircraft characterised by the type or position of power plants
  • B64D27/02—Aircraft characterised by the type or position of power plants
  • B64D27/30—Aircraft characterised by electric power plants
  • B64D27/31—Aircraft characterised by electric power plants within, or attached to, wings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D31/00—Power plant control systems; Arrangement of power plant control systems in aircraft
  • B64D31/02—Initiating means
  • B64D31/06—Initiating means actuated automatically
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
  • B64D31/00—Power plant control systems; Arrangement of power plant control systems in aircraft
  • B64D31/16—Power plant control systems; Arrangement of power plant control systems in aircraft for electric power plants
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
  • G05D1/40—Control within particular dimensions
  • G05D1/48—Control of altitude or depth
  • G05D1/482—Control of altitude or depth utilising or compensating for ground effect
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
  • G05D1/60—Intended control result
  • G05D1/65—Following a desired speed profile
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64C—AEROPLANES; HELICOPTERS
  • B64C9/00—Adjustable control surfaces or members, e.g. rudders
  • B64C2009/005—Ailerons
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D2105/00—Specific applications of the controlled vehicles
  • G05D2105/20—Specific applications of the controlled vehicles for transportation
  • G05D2105/22—Specific applications of the controlled vehicles for transportation of humans
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D2107/00—Specific environments of the controlled vehicles
  • G05D2107/25—Aquatic environments
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D2109/00—Types of controlled vehicles
  • G05D2109/20—Aircraft, e.g. drones
  • G05D2109/22—Aircraft, e.g. drones with fixed wings
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D2109/00—Types of controlled vehicles
  • G05D2109/30—Water vehicles
  • G05D2109/34—Water vehicles operating on the water surface
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D2109/00—Types of controlled vehicles
  • G05D2109/50—Vehicles specially adapted for two or more of space, air, land or water environments, e.g. amphibious vehicles

Definitions

• Figures 1A-1D illustrate various views of a craft, in accordance with example embodiments.
• Figure 2 illustrates a main hydrofoil deployment system of a craft, in accordance with example embodiments.
• Figure 3 illustrates a rear hydrofoil deployment system of a craft, in accordance with example embodiments.
• Figure 4 illustrates a battery system of a craft, in accordance with example embodiments
• Figure 5 illustrates a control system of a craft, in accordance with example embodiments.
• Figure 6A illustrates a craft in a hull-borne mode of operation, in accordance with example embodiments.
• Figure 6B illustrates a craft in a hydrofoil-borne maneuvering mode of operation, in accordance with example embodiments.
• Figure 7A illustrates a craft in a hydrofoil-borne takeoff mode of operation, in accordance with example embodiments.
• Figure 7B is a graph that illustrates various lift forces acting on a craft, in accordance with example embodiments.
• Figure 8 illustrates a craft in a wing-borne mode of operation, in accordance with example embodiments.
• Figure 9 illustrates airspeed control logic of a craft, in accordance with example embodiments.
• Figure 10 illustrates operations performed by airspeed control logic of the craft that facilitate reducing the airspeed of the craft using a first subset of propellers of the craft, in accordance with example embodiments.
• FIG. 11 illustrates profiles that relate the airspeed of the craft with rotation rates of propellers of the craft, in accordance with example embodiments
• Figure 12 illustrates operations performed by airspeed control logic of the craft that facilitate reducing the airspeed of the craft using first and second subsets of propellers of the craft, in accordance with example embodiments.
• Figure 13 illustrates profiles that relate the airspeed of the craft with rotation rates of propellers of the craft, in accordance with example embodiments.
• any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order.
• Aspects described herein are generally related to craft, such as aircraft that include multiple propellers.
• craft such as aircraft that include multiple propellers.
• the airspeed may be reduced by decreasing power to the various propellers of the craft.
• Lift on the craft, and therefore the altitude of the craft may be maintained by controlling other aspects of the craft, such as by gradually increasing the longitudinal pitch of the craft as the airspeed is reduced.
• Such conventional techniques may have various shortcomings in some instances, including but not limited to craft that fly within ground effect.
• such conventional techniques are characterized by a limited (or relatively slow) rate of deceleration, whereas an expedited (or relatively faster) rate of deceleration may be desired during some landing procedures contemplated to be performed by the craft disclosed herein. That is, it would take undesirably long to slow down the craft using such conventional techniques.
• reducing power to all the propellers on craft which utilize blown wing configurations by too much can in some situations lead to a sudden loss of lift and, therefore, altitude. This can be an especially relevant consideration for craft such as those disclosed herein that fly within ground effect.
• Some example craft disclosed herein are configured to address these aspects and other aspects. These craft examples selectively control the rotation rate of particular propeller(s) in a way that either induces or reduces drag on the craft without reducing (or increasing) lift on the craft to an undesirable extent.
• Some types of blown wing aircraft have several propellers on each wing.
• some blown wing aircraft may have four (i.e., two propellers on each each), six (i.e., three propellers on each wing), eight (i.e., propellers on each wing), or more propellers distributed across two wings.
• the airspeed of the craft can be changed by adjusting the rotation rate (i.e., propeller speed) of the propellers.
• the airspeed of a multi -propeller blown-wing craft can be increased by increasing the rotation speed of the propellers
• the airspeed of the multi -propeller blown-wing craft can be reduced by reducing the rotational speed of the propellers.
• the rotational speed of a particular group of propellers may affect the stability, control, and maneuverability of the craft more or less than another group of propellers based on where the propellers are located along wing relative to the body of the craft and the proximity of the propellers to the control surfaces along the wing.
• some example configurations disclosed herein include controlling the rotational speed of different groups of propellers separately from each other, particularly during a landing procedure, so as to reduce the overall airspeed of the craft without a corresponding reduction in control authority over the craft that would otherwise follow from a reduction in propeller rotational speed.
• some embodiments include controlling the rotational speed of a first group (or subset) of propellers separately from a second group (or subset) of propellers, including increasing or decreasing the rotational speed of the first group of propellers while keeping the rotational speed of the second group of propellers substantially constant, increasing or decreasing the rotational speed of the second group of propellers while keeping the rotational speed of the first group of propellers substantially constant, and/or increasing or decreasing the rotational speed of the first group of propellers by a first amount or rate of change while increasing or decreasing the rotational speed of the second group of propellers by a second amount or rate of change that is different than the first amount or rate of change.
• the first group (or subset) of propellers is located such that their corresponding wake over control surfaces such as ailerons, flaps, or flaperons is less than that of the second group (or subset) of propellers.
• control surfaces may be positioned closer to the wing tips in which case the first group of propellers may correspond to those propellers that are closest to the body of the craft and the second group of propellers may correspond to those propellers that are closer to the wing tips.
• the airspeed of the craft is changed by adjusting the rotation rate of only a subset of the propellers (e.g., the first subset of propellers) or by adjusting the rotation rate of the subset of the propellers to a greater or lesser degree than the degree to which the other propellers (e.g., the second subset) are adjusted.
• the airspeed can be lowered by reducing the rotation rate of the first subset of the propellers relative to the other propellers. That is, the first subset of propellers are “spun down” relative to the other propellers to reduce the airspeed. The spinning down of the first subset of propellers induces drag on the craft.
• the airspeed can be increased by increasing the rotation rate of the first subset of propellers relative to the other propellers. That is, the first subset of propellers are “spun up” to increase the airspeed. The spinning up of the first subset of propellers reduces drag on the craft and/or contributes forward thrust.
• the first subset of propellers include those propellers that have relatively less impact on the control and/or maneuverability of the craft 100 (as compared to other propellers), in at least some respect.
• the first subset of propellers include propellers positioned on the wing such that they correspond to a relatively smaller roll moment than at least some other propellers. That is, the first subset of propellers correspond to propellers positioned on the wing such that changes to their rotation rate contribute relatively less impact to the craft’s roll control than do changes to the rotation rate of the second subset of propellers.
• proximity of the propeller to one or more control elements of the wing affects the degree to which changes in that propeller’s rotational speed affect the control and/or maneuverability of the craft. That is, whether the propeller is positioned sufficiently close to a control surface such that propeller blows air over one or more control elements, such as an aileron, affects the degree to which changes in the rotational speed affect the control and/or maneuverability of the craft.
• the first subset of propellers include those propellers that are not positioned corresponding to an aileron, and/or that are located the furthest from the ailerons of the craft.
• This first subset of propellers can be spun down to reduce the airspeed of the craft while maintaining (or perhaps even increasing) the speed of other propellers closer to the control surfaces so as to reduce the airspeed while still maintaining an acceptable degree of control authority over the craft. In operation, this maintains relatively higher control authority as a result of air blown over the ailerons by the other propellers (i.e., the second subset of propellers) not in the first subset.
• the ailerons are located outboard, and the first subset of propellers (the propellers with the reduced rotation rate) are located relatively inboard.
• the first subset of propellers correspond to propellers positioned on the wing of the craft such that they contribute relatively less, or contribute the least, amount of lift on the craft.
• the first set of propellers may include propellers located further from flaps or flaperons than the propellers in the second set of propellers.
• the overall decrease of lift on the craft is mitigated by maintaining the rotation rate of the second set of propellers that are closer in proximity to the flaps and/or flaperons.
• the propellers in the second set of propellers contribute relatively more lift for the craft than the propellers in the first set.
• the propellers in the second set contribute the most amount of lift for the craft.
• the rotation rate for only one pair of propellers e.g., one on each wing is reduced. This approach will, in general, generate a significant amount of drag on the craft without meaningfully reducing the amount of lift on the craft.
• reducing the speed of the craft involves i) reducing the rotation rate of the second subset of propellers to some target rotation rate associated with a desired airspeed and ii) reducing the rotation rate of the first subset of propellers to a greater degree until the airspeed of the craft reaches the target airspeed.
• the rotation rate of the first subset of propellers may be subsequently increased to the target rotation rate (i.e., the rotation rate of the second subset of propellers), for example, as the airspeed approaches the target airspeed.
• WIG craft wing-in-ground effect craft
• WIG craft are capable of moving over a surface (e.g., earth or water) by gaining support from the reactions of the air against one or more surfaces of the craft.
• a surface e.g., earth or water
• the drag experienced by the craft is reduced.
• the drag on the craft is reduced when its distance from the ground is within about half the length of the aircraft’s wingspan.
• WIG craft that are configured to takeoff from water are described herein. These craft include retractable hydrofoils that are extended during takeoff to generate additional upward lift as the craft approaches take-off speeds. The upward lift raises the hull of the craft above the water. This action i) reduces the wetted surface area of the craft and therefore drag on the craft and ii) allows the craft to cruise through rough waters during takeoff without colliding with waves. Once airborne, the hydrofoils may be retracted.
• Some examples of these craft include and implement features disclosed in U.S. Patent Application No. 17/570,090, fded January 6, 2022 (herein after ’090 application), and U.S. Patent Application No.
• the ’090 and ‘480 applications are incorporated herein by reference in their entirety.
• the ’090 application describes, among other things, a seaglider that includes a pair of retractable hydrofoils (e.g., front and rear hydrofoils) that facilitate hydrofoil-borne operation of the craft.
• the ‘480 application describes, among other things, a seaglider that implements a bi-plane tail.
• FIG. 10 Other examples of craft to which the aspects described herein can be applied correspond to blown wing craft.
• air is blown over the wings of the craft by propellers, and the blowing of the air over the wings contributes meaningfully to the overall lift acting on the craft.
• Examples of these craft can include 4, 5, 6, or even more propellers on each wing.
• Some examples of the WIG craft described herein are blown wing craft. Some of these craft include six propellers on each wing, making these craft better suited for commercial travel.
• FIGS 1A-1D illustrate different views of an example of a craft 100.
• some examples of the craft 100 include a hull 102, a main wing 104, a tail 106, a main hydrofoil assembly 108, and a rear hydrofoil assembly 110.
• Hull Hull
• Some examples of the craft 100 operate in a first waterborne mode for an extended period of time, during which the hull 102 is at least partially submerged in water.
• some examples of the hull 102 are configured to be watertight, particularly for surfaces of the hull that contact the water during this first waterborne operational mode.
• some examples of the hull 102, as well as the entirety of the craft 100 are configured to be passively stable on all axes when floating in water.
• some examples of the hull 102 include a keel (or centerline) 112, which provides improved stability and other benefits described below.
• the craft 100 include various mechanisms for adjusting the center of mass of the craft 100 so that the center of mass aligns with the center of buoyancy of the craft 100.
• a battery system (described in further detail below in connection with Figure 4) of the craft 100 is electrically coupled to one or more moveable mounts. Some examples of the mounts are moved by one or more servo motors or the like.
• a control system of the craft 100 is configured to detect a change in its center of buoyancy, for instance, by detecting a rotational change via an onboard gyroscope, and responsively operate the servo motors to move the battery system until the gyroscope indicates that the craft 100 has stabilized.
• the craft 100 include a ballast system for pumping water or air to various tanks distributed throughout the hull 102 of the craft 100.
• the ballast system facilitates adjusting the center of mass of the craft 100 so that the center of mass aligns with the center of buoyancy of the craft 100.
• Other example systems may be used to control the center of mass of the craft 100 as well.
• some examples of the hull 102 are configured to reduce drag forces when both waterborne and wing-borne.
• some examples of the hull 102 have a high length-to-beam ratio (e.g., greater than or equal to 8), which facilitates reducing hydrodynamic drag forces when the craft 100 is under forward waterborne motion.
• Some examples of the keel 112 are curved or rockered to improve maneuverability when waterborne.
• some examples of the hull 102 are configured 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 102.
• some examples of the main wing 104 include an outrigger 114 at each end of the main wing 104.
• the outriggers 114 (which are sometimes referred to as “wing-tip pontoons”) are configured to provide a buoyant force to the main wing 104 when submerged or when otherwise in contact with the water, which improves the stability of the craft 100 during waterborne operation.
• some examples of the main wing 104 have a gull-wing shape such that the outriggers 114 at the ends of the main wing 104 are at the lowest point of the main wing 104 and are positioned approximately level with (or slightly above) a waterline of the hull 102 when the hull 102 is waterborne.
• the main wing 104 have a high aspect ratio, which is defined as the ratio of the span of the main wing 104 to the mean chord of the main wing 104.
• the aspect ratio of the main wing 104 is greater than or equal to five, or greater than or equal to six, but other example aspect ratios are possible as well.
• Such wings tend to have reduced pitch stability and maneuverability due to lower roll angular acceleration. These issues are ameliorated by various mechanisms described below. On the other hand, such wings tend to have increased roll stability and increased efficiency resulting from higher lift-to-drag ratios. Further, high aspect ratio wings provide a longer leading edge for the mounting of a distributed propulsion system along the wing.
• some examples of the main wing 104 include a number of electric motor propeller assemblies 116 distributed across a leading edge of the main wing 104.
• This arrangement corresponds to a blown-wing propulsion system.
• Arranging the propeller assemblies 116 in this manner increases the speed of air moving over the main wing 104, which increases the lift generated by the main wing 104.
• This increase in lift allows the craft 100 to take off and become wing-borne at slower vehicle speeds. This facilitates, for example, taking off on water which can be difficult at higher speeds due to the various forces that would otherwise act on the craft 100.
• the electric motor propeller assemblies 116 tend to be much lighter, less complex, and smaller than the liquid-fueled engines used on conventional craft. Some examples of the electric motor propeller assemblies 116 are controlled by an electronic speed controller and powered by an onboard battery system (e.g., a lithium-ion system, magnesium-ion system, lithium-sulfur system, etc ). Some examples of the electric motor propeller assemblies 116 are controlled by a fuel cell or a centralized liquid-fueled electricity generator.
• the onboard electrical supply system includes 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 wing-borne operation, each of which are described in further detail below).
• a first battery system configured to deliver large amounts of power during takeoff
• 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 wing-borne operation, each of which are described in further detail below.
• the positioning of the electric motor propeller assemblies 116 along the leading edge of the main wing 104 is determined based on a variety of factors including, but not limited to, (i) the required total thrust for all modes of operation of the craft 100, (ii) the thrust generated by each individual propeller of the propeller assemblies 116, (iii) the radius of each propeller in the respective propeller assemblies 116, (iv) the required tip clearance between each propeller and the surface of the water, and (v) the additional freestream speed over the main wing 104 required for operation.
• the number of propeller assemblies 116 is symmetrical across both sides of the hull 102.
• the propeller assemblies 116 are identical.
• the propeller assemblies 116 have different propeller radii or blade configurations along the span so long as the configuration is symmetrical across the hull 102. The different radii facilitate adequate propeller tip clearance from the water or vehicle structure.
• the different propellers are optimized for different operational conditions, such as wing-borne cruise. The propeller placement and configuration may vary to increase the airflow over the main wing 104 or tail system 106 to improve controllability or stability. While eight total propeller assemblies 116 are illustrated, the actual number of propeller assemblies 116 can vary based on the requirements of the craft 100.
• the propeller assemblies 116 have different pitch settings or variable pitch capabilities based on their position on the main wing 104. For instance, in some examples, a subset of the propeller assemblies 116 have fixed-pitch propellers sized for cruise speeds, while the remainder of the propeller assemblies 116 have fixed-pitch propellers configured for takeoff or can allow for varying the propeller’s pitch.
• different propeller assemblies 116 are turned off or have reduced rotational speeds during different modes of operation.
• one or more of the propeller assemblies 116 may be turned off or have reduced rotational speeds in a manner that generates asymmetrical thrust. This may create a yawing moment on the craft 100, allowing the craft 100 to turn without large bank angles and increasing the turning maneuverability of the craft 100.
• the craft 100 may increase the rotational speeds of the propellers of one or more of propeller assemblies 116g-l while decreasing the rotational speeds of the propellers of one or more of propeller assemblies 116a-f.
• the craft 100 may increase the rotational speeds of the propellers of one or more of propeller assemblies 116a-f while decreasing the rotational speeds of the propellers of one or more of propeller assemblies 116g-l .
• varying rotational speeds or propeller pitches may be used to yaw or roll the aircraft in flight or while foiling due to varied forces and lift distributions imposed over the wing and its control surfaces or in general used to tailor the lift distribution across the wing for optimized efficiency.
• the propeller assemblies may tilt to vector thrust either to provide directly more vertical lift or to change how the wing is blown depending on the mode of operation so as to tailor the blown lift distribution.
• main wing 104 include one or more aerodynamic control surfaces, such as flaps 118 and ailerons 120. Some examples of these controls comprise movable hinged surfaces on the trailing or leading edges of the main wing 104 for changing the aerodynamic shape of the main wing 104. Some examples of the flaps 118 are configured to extend downward below the main wing 104 to reduce stall speed and create additional lift at low airspeeds, while some examples of the ailerons 120 are configured to extend upward above the main wing 104 to decrease lift on one side of the main wing 104 and induce a roll moment in the craft 100.
• flaps 118 are configured to extend downward below the main wing 104 to reduce stall speed and create additional lift at low airspeeds
• ailerons 120 are configured to extend upward above the main wing 104 to decrease lift on one side of the main wing 104 and induce a roll moment in the craft 100.
• the ailerons 120 are additionally configured to extend downward below the main wing 104 in a flaperon configuration to help the flaps 118 generate additional lift on the main wing 104, which, in some examples, is used to either create a rolling moment or additional balanced lift depending on coordinated movement of both ailerons.
• Some examples of the flaps 118 and ailerons 120 include one or more actuators for raising and lowering the flaps 118 and ailerons 120.
• the flaps 118 include one or more of plain flaps, split flaps, slotted flaps, Fowler flaps, slotted Fowler flaps, Gouge flaps, lunkers flaps, or Zap flaps.
• the flaps 118 (and the ailerons 120 when configured as flaperons) are positioned to be in the wake of one or more of the propeller assemblies 116.
• the ailerons 120 are positioned so that they are in the wake of one or more of the propeller assemblies 116 to increase the effectiveness of the ailerons at low forward velocities.
• Some of the propeller assemblies 116 are positioned so that no ailerons 120 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.
• 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 106 include a vertical stabilizer 122, a horizontal stabilizer 124, and one or more control surfaces, such as elevators 126. Similar to the flaps 118 and ailerons 120, some examples of the elevators 126 comprise movable hinged surfaces on the trailing or leading edges of the horizontal stabilizer 124 for changing the aerodynamic shape of the horizontal stabilizer 124 to control a pitch of the craft 100.
• Some examples of the horizontal stabilizer 124 are combined with the elevator 126, creating a fully articulating horizontal stabilizer (e.g., a stabilator). Raising the elevators 126 above the hinge point creates a net downward force on the tail system and causes the craft 100 to pitch upward. Lowering the elevators 126 below the hinge point creates a net upward force on the horizontal stabilizer 124 and causes the craft 100 to pitch downward.
• Some examples of the elevators 126 include actuators, which are operated by a control system of the craft 100 to raise and lower the elevators 126.
• tail 106 include a rudder 128.
• the rudder 128 comprise a movable hinged surface on the trailing edge of the vertical stabilizer 122 for changing the aerodynamic shape of the vertical stabilizer 122 to control the yaw of the craft 100 when operating in an airborne mode.
• the rudder 128 additionally changes a hydrodynamic shape of the hull 102 to control the yaw of the craft 100 when operating in a waterborne mode.
• the rudder 128 is positioned low enough on the tail 106 that the rudder 128 is partially or entirely submerged when the hull 102 is floating in water.
• the rudder 128 is positioned partially or entirely below the waterline of the hull 102.
• Some examples of the rudder 128 include one or more actuators, which are operated by a control system of the craft 100 to rotate the hinged surface of the rudder 128 to the left or right of the vertical stabilizer 122. Actuating the rudder 128 to the left (relative to the direction of travel) causes the craft 100 to yaw left. Actuating the rudder 128 to the right (relative to the direction of travel) causes the craft 100 to yaw right.
• the rudder 128 may be used in combination with any of the other mechanisms disclosed herein for controlling the yaw of the craft 100, including in combination with the ailerons 120 during airborne operation and in combination with varying the rotational speeds of different ones of the propeller assemblies 116 to help improve the maneuverability of the craft 100 during waterborne operation.
• the tail 106 include one or more vertical stabilizers 122a, 122b, 122n, one or more horizontal stabilizers 124a, 124b, one or more control surfaces, such as elevators 126, and one or more tail flaps 127 for enhanced pitch control configured to exert enhanced net downward force on the tail system.
• a conventional solution would be to increase the span of the tail so that the elevator generates more force; however, a resultant consequence of increasing the span of the tail is that the entire tail must be stronger and heavier, which can result in undesired reduction of payload and efficiency.
• the present configuration provides improved performance by providing a tail 106 having a first horizontal stabilizer 124a and a second horizontal stabilizer 124b. It should be understood that one or more additional horizontal stabilizers can be used.
• a first horizontal stabilizer 124a is a lower horizontal stabilizer relative to a second horizontal stabilizer 124b.
• the horizontal stabilizers in some examples can be interchanged for performance purposes (e.g., the disclosed structure of the first horizontal stabilizer 124a can be incorporated in the upper horizontal stabilizer and the disclosed structure of the second horizontal stabilizer 124b can be incorporated in the lower horizontal stabilizer).
• the structure, shape, and/or performance of each horizontal stabilizer can be tailored as desired such that the lower horizontal stabilizer (in this example, the first horizontal stabilizer 124a) is more likely to experience aerodynamic effect from being in the wake of the blown-wing propulsion system disclosed herein or associated wake produced by alternative propulsion systems.
• the horizontal stabilizers 124a, 124b include one or more aerodynamic control surfaces, such as tail flaps 127 and elevators 126, which may comprise movable hinged surfaces on the trailing or leading edges of the horizontal stabilizer 124a, 124b for changing the aerodynamic shape of the respective horizontal stabilizer 124a, 124b. It should be recognized that at least one of the horizontal stabilizers 124a, 124b can be sized, shaped, and/or spaced relative to a second of the horizontal stabilizers 124a, 124b to enhance or minimize the aerodynamic effect on the adjacent stabilizers.
• At least one of the horizontal stabilizers 124a, 124b can be actuated in an opposing direction.
• at least one of the horizontal stabilizers 124a, 124b can define a ratio of a surface area of the first horizontal stabilizer to a surface area of the second horizontal stabilizer in the range of 0.9 to 1.6.
• the surface area of the first horizontal stabilizer is 5.7 m2
• the surface area of the second horizontal stabilizer is 3.9 m2, both have a chord of about 1 m and a vertical separation of 1.8 m.
• a vertical separation distance between the first horizontal stabilizer and the second horizontal stabilizer is in the range of 0.25 to 0.75 of the lower horizontal stabilizer span.
• a vertical separation distance can be dependent on the required rudder authority and thus elevator size (driven by, e.g., yaw stability, or the need to counteract asymmetric thrust following powerplant failure).
• a sweep offset moves the center of pressure further aft from the center of gravity, thus allowing the airfoil of the horizontal stabilizer to have less surface area overall, thus being smaller and lighter.
• a dihedral in the bottom surface of the horizontal stabilizer adds stability.
• the box tail design itself increases the efficiency due to the elimination of wingtip vortices of a typical tail.
• a lower horizontal stabilizer may have approximately a 15% thickness-to-chord ratio to support the weight of the upper components, whereas the vertical and upper surfaces may be thinner, such as, for example, 10% thickness-to- chord ratio due to reduced structural load requirement, which enables the upper horizontal stabilizer to be more efficient (lower drag).
• the left and right elevator surfaces 126 can be controlled independently and/or differentially to create a rolling moment, thereby enabling the wing ailerons 120 to be made smaller. The smaller wing ailerons 120 further enable larger flaps 118.
• tail flaps 127 are configured to selectively extend upward above the horizontal stabilizer 124 for changing a surface area, camber, aspect ratio, and/or shape of the horizontal stabilizer 124.
• the tail flaps 127 may include, for example, one or more of plain flaps, split flaps, slotted flaps, Fowler flaps, slotted or double-slotted Fowler flaps, Gouge flaps, Junkers flaps, or Zap flaps.
• tail flaps 127 serve to change an angle of attack of the horizontal stabilizer 124, change a chord line of the horizontal stabilizer 124, change a surface area of the horizontal stabilizer 124, and/or otherwise increase the net effective downwardly directed lift of the horizontal stabilizer 124.
• Such configurations effectively reduce the speed at which the horizontal stabilizer 124 becomes aerodynamically effective by creating additional net downward force at low airspeeds to aid in exerting a nose-up pitching moment of the craft 100.
• the elevators 126 may be configured for changing the aerodynamic shape of the horizontal stabilizer 124 to further control or vary a pitch of the craft 100.
• the tail flaps 127 are deployed for takeoff (e.g., transition from hydrofoil-borne mode to airborne mode) and landing (e.g., transition from airborne mode to hull-borne mode) to generate additional downforce on the tail system when additional pitch-up moment is required.
• Tail flaps 127 can be stowed for other phases of operation, such as hull-borne mode, to reduce downforce on the tail system and reduce drag.
• the elevators 126 are additionally configured to extend upward above the horizontal stabilizer 124 in a flaperon-like configuration (yet with elevators, rather than ailerons) to help the tail flaps 127 generate additional downward force on the horizontal stabilizer 124, which may be used to either create a pitching moment or additional balanced downward force.
• the tail flaps 127 and elevators 126 may each include one or more actuators 125 for raising and lowering the tail flaps 127 and elevators 126, singly or in combination.
• the actuators 125 can comprise any system configured to selectively actuate the associated system, such as but not limited to a flap track system (integrated into vertical stabilizers 122a, 122b, 122n, which can reduce complex hinge systems or external arms, thereby reducing wetted area and excrescences drag), an electric servo motor mounting within the vertical stabilizers 122a, 122b, 122n and/or horizontal stabilizers 124a, 124b, and/or a central vertical strut system generally mounted in the hull 102 or the fuselage of the craft 100 (to provide the potential for reduced cross-sectional area and associated drag).
• a flap track system integrated into vertical stabilizers 122a, 122b, 122n, which can reduce complex hinge systems or external arms, thereby reducing wetted area and excrescences drag
• the elevators 126 and/or the tail flaps 127 are positioned so that they are in the wake 129 of one or more of the propeller assemblies 116 of main wing 104.
• the elevators 126 and/or the tail flaps 127 may be positioned so that they are in the wake 129 of one or more of the propeller assemblies 116 to increase the effectiveness of the elevators at low forward velocities.
• the propeller assemblies 116 are positioned so that no elevators 126 and/or tail flaps 127 are in the wake 129 to ensure consistent and/or predictable aerodynamic forces, independent of power application, are exerted during critical operational phases.
• the propeller assemblies 116 are positioned so that the elevators 126 are in their wake 129 and the tail flaps 127 are not in the wake 129 (e.g., above the wake 129) and are exposed to clean air 131. It should be understood that positioning of the tail flaps 127 in the second horizontal stabilizer 124b, or at a distance above the center of gravity of the craft 100, will have the added unexpected benefit of creating additional nose-up pitching moment as a result of induced drag acting about the center of gravity causing the craft 100 to pitch upward.
• the elevators 126 comprise movable hinged surfaces on the trailing or leading edges of the horizontal stabilizer 124 for changing the aerodynamic shape of the horizontal stabilizer 124 to control a pitch of the craft 100.
• the horizontal stabilizer 124 may be combined with the elevator 126, creating a fully articulating horizontal stabilizer (e.g., a stabilator). Raising the elevators 126 above the hinge point creates a net downward force on the tail system and causes the craft 100 to pitch upward. Lowering the elevators 126 below the hinge point creates a net upward force on the horizontal stabilizer 124 and causes the craft 100 to pitch downward.
• the elevators 126 may include actuators, which may be operated by a control system of the craft 100 in order to raise and lower the elevators 126.
• the tail 106 includes one or more rudders 128a, 128b, 128n.
• the rudders 128a, 128b, 128n may each comprise a movable hinged surface on the trailing edge of the corresponding vertical stabilizers 122a, 122b, 122n for changing the aerodynamic shape of the vertical stabilizer 122 to control the yaw of the craft 100 when operating in an airborne mode.
• rudders 128a, 128b, 128n can operate independently or in combination as desired.
• rudders 128a, 128b, 128n can be used as redundant systems, particularly useful in the event of one or more failures.
• the rudders 128a, 128b, 128n additionally change a hydrodynamic shape of the hull 102 to control the yaw of the craft 100 when operating in a waterborne mode.
• the rudders 128a, 128b, 128n may be positioned low enough on the tail 106 that one or more of the rudders 128a, 128b, 128n is partially or entirely submerged when the hull 102 is floating in water. Namely, the rudders 128a, 128b, 128n may be positioned partially or entirely below a waterline of the hull 102.
• the rudders 128a, 128b, 128n may include one or more actuators, which may be operated by a control system of the craft 100 in order to rotate the hinged surface of the rudders 128a, 128b, 128n to the left or right of the vertical stabilizer 122. Actuating the rudders 128a, 128b, 128n to the left (relative to the direction of travel) causes the craft 100 to yaw left. Actuating the rudders 128a, 128b, 128n to the right (relative to the direction of travel) causes the craft 100 to yaw right.
• the rudders 128a, 128b, 128n may be used in combination with any of the other mechanisms disclosed herein for controlling the yaw of the craft 100, including in combination with the ailerons 120 during airborne operation and in combination with varying the rotational speeds of different ones of the propeller assemblies 116 to help improve the maneuverability of the craft 100 during waterborne operation.
• tail 106 having one or more vertical stabilizers 122a, 122b, 122n and one or more horizontal stabilizers 124a, 124b, can result in a box-like assembly, wherein the vertical stabilizers are generally coupled to the horizontal stabilizers to form a reinforced box-like construction.
• This box-like construction provides enhanced structural integrity that enables tail 106 of some examples to be lighter and/or smaller than otherwise constructed.
• Some examples of the craft 100 include a distributed propulsion system on the tail 106, which may be similar to the distributed propulsion system of propeller assemblies 116 on the main wing 104.
• a distributed propulsion system may provide similar benefits of increasing the freestream velocity over the control surfaces (e.g., the elevators 126 and/or the rudder 128) to allow for increased pitch and yaw control of the craft 100 at lower travel speeds.
• the control surfaces e.g., the elevators 126 and/or the rudder 1228
• determining the number and size of propeller assemblies to include on the tail 106 one may apply the same factors described above when determining the number and size of propeller assemblies to include on the main wing 104.
• the craft 100 include a main hydrofoil assembly 108 and a rear hydrofoil assembly 110.
• the main hydrofoil assembly 108 is positioned proximate to the middle or bow of the craft 100
• the rear hydrofoil assembly 110 is positioned proximate to the stem.
• some examples of the main hydrofoil assembly 108 is positioned between the bow and a midpoint (between the bow and stern) of the craft 100
• some examples of the rear hydrofoil assembly 110 is positioned below the tail 106 of the craft 100.
• the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 are configured to facilitate the breaking of contact between the hull of the craft and the water surface during takeoff, which, as noted above, can otherwise be challenging in some conventional craft designs.
• Some examples of the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 are configured to be retractable, large enough to lift the entire craft out of the water and not impact the water surface, and to enable sustained operation in the hydrofoil-borne mode (where the entire weight of the craft is supported by the one or more hydrofoil assemblies).
• main hydrofoil assembly 108 includes a main hydrofoil 130, one or more main hydrofoil struts 1 2 that couple the main hydrofoil 130 to the hull 102, and one or more main hydrofoil control surfaces 134.
• rear hydrofoil assembly 110 include a rear hydrofoil 136, one or more rear hydrofoil struts 138 that couple the rear hydrofoil 136 to the hull 102, and one or more rear hydrofoil control surfaces 140.
• main hydrofoil 130 and the rear hydrofoil 136 take the form of one or more hydrodynamic lifting surfaces (also referred to as “foils”) configured to be operated partially or entirely submerged underwater while the hull 102 of the craft 100 remains above and clear of the water’s surface.
• the hydrofoils In operation, as the craft 100 moves through water with the main hydrofoil 130 and the rear hydrofoil 136 submerged, the hydrofoils generate a lifting force that causes the hull 102 to rise above the surface of the water. In general, the lifting force generated by the hydrofoils must be at least equal to the weight of the craft 100 to cause the hull 102 to rise above the surface of the water.
• the lifting force of the hydrofoils depends on the speed and angle of attack at which the hydrofoils 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 102 is elevated above the surface of the water during hydrofoil -borne operation is limited by the length of the one or more main hydrofoil struts 132 that couple the main hydrofoil 130 to the hull 102 and the length of the one or more rear hydrofoil struts 138 that couple the rear hydrofoil 136 to the hull 102.
• the main hydrofoil strut 132 and the rear hydrofoil strut 138 are long enough to lift the hull 102 at least five feet above the surface of the water during hydrofoil-borne operation, which facilitates operation in substantially choppy waters.
• Struts of other lengths may be used as well. For instance, in some examples, longer struts that allow for better wave-isolation of the hull 102 (but at the expense of the stability of the craft 100 and increasing complexity of the retraction system) are utilized.
• 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 generated by the hydrofoil and increases drag. Therefore, it is desirable to reduce the onset of cavitation by designing the main hydrofoil 130 and the rear hydrofoil 136 in a way that allows the hydrofoils to operate at higher speeds (e.g., -20-45 mph) and across the entire required hydrofoil-borne speed envelope before cavitation occurs.
• higher speeds e.g., -20-45 mph
• the onset of cavitation is controlled based on the geometric design of the main hydrofoil 130 and the rear hydrofoil 136.
• the structural design of the main hydrofoil 130 and the rear hydrofoil 136 is configured to allow the surfaces of the hydrofoils to flex and twist at higher speeds, which may reduce loading on the hydrofoils and delay the onset of cavitation.
• the distributed blown-wing propulsion system described above further facilitates the delay of onset of cavitation on the main hydrofoil 130 and the rear hydrofoil 136. Cavitation is caused by both (i) the amount of lift 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 generated by the hydrofoil delays the onset of cavitation.
• the blown-wing propulsion system creates additional lift on the main wing 104, the amount of lift exerted on the main hydrofoil 130 and the rear hydrofoil 136 to lift the hull 102 out of the water is reduced. Further, because the main hydrofoil 130 and the rear hydrofoil 136 do not need to generate as much lift to raise the hull 102 out of the water, their angles of attack may be reduced as well, which further delays the onset of cavitation. In some examples, combining the blown-wing propulsion system with the hydrofoil designs described herein facilitates operating the craft 100 in a hydrofoil-borne mode at speeds above 35 knots before cavitation occurs.
• main hydrofoil assembly 108 and the rear hydrofoil assembly 110 include one or more main and rear hydrofoil control surfaces 134, 140, respectively.
• main hydrofoil control surfaces 134 include one or more hinged surfaces on a trailing or leading edge of the main hydrofoil 130 as well as one or more actuators which are operated by the control system of the craft 100 to rotate the hinged surfaces so that they extend above or below the main hydrofoil 130.
• Some examples of the main hydrofoil control surfaces 134 on the main hydrofoil 130 are operated in a similar manner as the flaps 118 and ailerons 120 on the main wing 104 of the craft 100.
• lowering the control surfaces 134 to extend below the main hydrofoil 130 changes the hydrodynamic shape of the main hydrofoil 130 in a manner that generates additional lift on the main hydrofoil 130, similar to the aerodynamic effect of lowering the flaps 118.
• asymmetrically raising one or more of the control surfaces 134 e.g., raising a control surface 134 on only one side of the main hydrofoil 130 changes the hydrodynamic shape of the main hydrofoil 130 in a manner that generates a roll force on the main hydrofoil 130, similar to the aerodynamic effect of raising one of the ailerons 120.
• the rear hydrofoil control surfaces 140 include one or more hinged surfaces on a trailing or leading edge of the rear hydrofoil 136 as well as one or more actuators, which are operated by the control system of the craft 100 to rotate the hinged surfaces so that they extend above or below the rear hydrofoil 136.
• the rear hydrofoil control surfaces 140 on the rear hydrofoil 136 are operated in a similar manner as the elevators 126 on the tail 106 of the craft 100.
• lowering the control surfaces 140 to extend below the rear hydrofoil 136 changes the hydrodynamic shape of the rear hydrofoil 136 in a manner that causes the craft 100 to pitch downwards, similar to the aerodynamic effect of lowering the elevators 126.
• raising the control surfaces 140 to extend above the rear hydrofoil 136 changes a hydrodynamic shape of the rear hydrofoil 136 in a manner that causes the craft 100 to pitch upwards, similar to the aerodynamic effect of raising the elevators 126.
• one or both of the main hydrofoil control surfaces 134 or the rear hydrofoil control surfaces 140 include rudder-like control surfaces similar to the rudder 128 on the tail 106 of the craft 100.
• some examples of the main hydrofoil control surfaces 134 include one or more hinged surfaces on a trailing edge of the main hydrofoil strut 132 as well as one or more actuators, which are operated by the control system of the craft 100 to rotate the hinged surfaces so that they extend to the left or right of the main hydrofoil strut 132.
• some examples of the rear hydrofoil control surfaces 140 include one or more hinged surfaces on a trailing edge of the rear hydrofoil strut 138 as well as one or more actuators, which are operated by the control system of the craft 100 in order to rotate the hinged surfaces so that they extend to the left or right of the rear hydrofoil strut 138.
• actuating the main hydrofoil control surfaces 134 or the rear hydrofoil control surfaces 140 in this manner changes the hydrodynamic shape of the main hydrofoil strut 132 or the rear hydrofoil strut 138, respectively, which facilitates controlling the yaw of the craft 100 when operating in a waterborne or hydrofoil-borne mode, similar to the effect of actuating the rudder 128 of the craft 100, as described above.
• a control system of the craft 100 actuates the entire main hydrofoil 130 and/or the entire rear hydrofoil 136 themselves.
• the craft 100 includes one or more actuators for rotating the main hydrofoil 130 and/or the rear hydrofoil 136 around the yaw axis.
• the craft 100 includes one or more actuators for controlling the angle of attack of the main hydrofoil 130 and/or the rear hydrofoil 136 (i.e., rotating the main hydrofoil 130 and/or the rear hydrofoil 136 around the pitch axis).
• Some examples of the craft 100 include one or more actuators for rotating the main hydrofoil 130 and/or the rear hydrofoil 136 around the roll axis. Some examples of the craft 100 include one or more actuators for changing a camber or shape of the main hydrofoil 130 and/or the rear hydrofoil 136. Some examples of the craft 100 include one or more actuators for flapping the main hydrofoil 130 and/or the rear hydrofoil 136 to help propel the craft 100 forward or backward. Other examples are possible as well.
• some examples of the craft 100 dynamically control an extent to which the main hydrofoil 130 and/or the rear hydrofoil 136 are deployed based on an operational mode (e.g., hull-borne, hydrofoil-borne, or wing-borne modes) of the craft 100.
• an operational mode e.g., hull-borne, hydrofoil-borne, or wing-borne modes
• the rear hydrofoil assembly 110 is 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.
• the main hydrofoil assembly 108 is partially retracted to reduce the distance between the hull of the vehicle and the water’s surface. This increases the amount of lift generated by the main wing 104 by operating the wing closer to the surface of the water, increasing the effects of the aerodynamic ground effect.
• main hydrofoil assembly 108 and rear hydrofoil assembly 110 interface with a deployment system that facilitates retracting the respective hydrofoil assemblies 108, 110 into or toward the hull 102 for hull-borne or wing-borne operation and for extending the respective hydrofoil assemblies 108, 110 below the hull 102 for hydrofoil- borne operation.
• the deployment system is used in connection with extending, retracting, and/or otherwise controlling the positioning of the hydrofoil assemblies 108, 110 during takeoff when the craft is transitioning from hydrofoil-borne operation to wing-borne operation.
• Figure 2 illustrates an example of a main hydrofoil deployment system 200 that facilitates retracting and extending of the main hydrofoil assembly 108.
• the main hydrofoil deployment system 200 take the form of a linear actuator that includes one or more brackets 202 that couple the main hydrofoil assembly 108 (by way of the main hydrofoil strut 132) to one or more vertical tracks 204.
• Some examples of the brackets 202 are configured to move vertically along the tracks 204, such that when the brackets 202 move vertically along the tracks 204, the main hydrofoil assembly 108 likewise moves vertically.
• Some examples of the brackets 202 are coupled to a leadscrew 206 that, when rotated, causes vertical movement of the brackets 202. Some examples of the leadscrew 206 are rotatable by any of various sources of torque, such as an electric motor coupled to the leadscrew 206 by a gear assembly 208.
• Some examples of the main hydrofoil deployment system 200 further include one or more sensors 210 configured to detect a vertical position of the main hydrofoil assembly 108. For example, a first sensor senses when the main hydrofoil assembly 108 has reached a fully retracted position and a second sensor senses when the main hydrofoil assembly 108 has reached a fully extended position.
• the main hydrofoil deployment system 200 may include additional sensors for detecting additional discrete positions or continuous positions of the main hydrofoil assembly 108. Some examples of the sensors are included as part of, or otherwise configured to communicate with, the control system of the craft 100 to provide the control system with data that indicates the position of the main hydrofoil assembly 108. Some examples of the control system use this data to determine whether to operate the electric motor to retract or extend the main hydrofoil assembly 108.
• the main hydrofoil deployment system 200 includes a locking or braking mechanism for holding the main hydrofoil strut 132 in a fixed position (e.g., in a fully retracted or fully extended position).
• An example of the locking mechanism corresponded to a dual-action mechanical brake that is coupled to the electric motor, the leadscrew 206, or the gear assembly.
• the main hydrofoil deployment system 200 may include any of various linear actuators now known or later developed that are capable of retracting and extending the main hydrofoil assembly 108.
• Figure 3 illustrates an example of a rear hydrofoil deployment system 300 that facilitates retracting and extending the rear hydrofoil 136.
• some examples of the rear hydrofoil deployment system 300 include an actuator 305 to the rear hydrofoil strut 138. When actuated, the actuator 305 causes the rear hydrofoil strut 138 to raise or lower by causing the rear hydrofoil strut 138 to slide vertically along a shaft 307.
• the rudder 128 is mounted to the shaft 307 such that, when the actuator 305 raises the rear hydrofoil strut 138, the rear hydrofoil strut 138 retracts at least partially into the rudder 128.
• the rear hydrofoil deployment system 300 include one or more servo motors configured to rotate the rear hydrofoil strut 138 around the shaft.
• the rear hydrofoil strut 138 is 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.
• the same servo motor can also be used to control the rotation of the rudder 128.
• the actuator 305 of the rear hydrofoil deployment system 300 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 110. Further, in some examples, the actuator 305 has a non-unitary actuation ratio such that a given movement of the actuator 305 causes a larger corresponding induced movement of the rear hydrofoil assembly 110. This can help allow for faster retractions of the rear hydrofoil assembly 110, which may be beneficial during takeoff, as described in further detail below.
• main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 are configured such that, when fully retracted, the hydrofoil assembly is flush, conformal, or tangent to the hull 102.
• some examples of the hull 102 include one or more recesses configured to receive the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110.
• some examples of the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 have a shape such that when the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 are fully retracted into the recesses of the hull 102, the outer contour of the hull 102 forms a substantially smooth transition at the intersection of the hull 102 and the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110.
• main hydrofoil assembly 108 and/or the rear hydrofoil protrude slightly below the hull 102 when retracted.
• These examples of the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 are configured to have a non-negligible effect on the aerodynamics of the craft 100.
• Some examples of the craft 100 are configured to leverage these effects to provide additional control of the craft 100. For instance, in some examples, when the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 are retracted but still exposed, the exposed hydrofoil is manipulated in flight to impart forces and moments on the craft 100 similar to an aero-control surface.
• hydrofoil assemblies 108, 110 disclosed herein are mounted on a pivot that is locked underwater but is unlocked to allow the hydrofoil to move around the pivot in the air.
• the control surfaces act like trim tabs and are able to effect movement of the entire unlocked, pivoting hydrofoil, which would otherwise require impractically large and heavy servo motors.
• This configuration facilitates unlocking and moving of the hydrofoil using 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.
• some examples of the main hydrofoil assembly 108 are configured to be retractable.
• Some examples of the hull 102 include openings through which the strut 132 of the main hydrofoil assembly 108 are retracted and extended.
• Some examples of the hull 102 are configured to isolate water that enters through these openings (e g., when the hull 102 contacts the water surface) and to allow for the water to drain from the hull 102 after the hull 102 is lifted out of the water.
• some examples of the hull 102 include pockets 142 on each side of the hull 102 aligned above the strut 132.
• the pockets 142 are isolated from the remainder of the interior of the hull 102 so that water that accumulates in the pockets 142 does not reach any undesired areas (e.g., the cockpit, passenger seating area, areas that house the battery system 400, components of the control system of the craft 100, etc.). Further, some examples of the pockets 142 include venting holes or other openings located at or near the bottom of the pockets 142. The venting openings are configured to allow water that enters the pockets 142 to vent out of the pockets 142 when the hull 102 is lifted out of the water.
• main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 include one or more propellers for additional propulsion when submerged underwater.
• one or more propellers are mounted to the main hydrofoil 130 and/or the rear hydrofoil 136.
• the propellers are configured to provide additional propulsion force to the craft 100 during hydrofoil -borne or hull -borne operation.
• propellers are mounted to the hull 102.
• the propellers are submerged during hull-borne operation.
• the propellers are configured to provide additional propulsion force to the craft 100 during hull-borne operation.
• main and/or rear hydrofoil assemblies 108, 110 include various failsafe mechanisms in case of malfunction. For instance, in some examples, when one or both of the main and rear hydrofoil deployment systems 200, 300 cannot be retracted due to a malfunction, the craft 100 is configured to jettison the malfunctioning assembly. In this regard, some examples of the main and/or rear hydrofoil assemblies 108, 110 are coupled to the hull 102 by a releasable latch. Some examples of the control system of the craft 100 are configured to identify a retraction malfunction (e.g., based on data received from the positional sensors 210) and responsively open the latch to release the connection between the hull 102 and the malfunctioning hydrofoil assembly.
• a retraction malfunction e.g., based on data received from the positional sensors 210
• the weight of the malfunctioning hydrofoil assembly is sufficient to jettison the malfunctioning hydrofoil assembly out of the hull 102 when the latch is opened.
• the craft 100 include an actuator or some other mechanism to jettison the malfunctioning hydrofoil assembly out of the hull 102.
• the main and/or rear hydrofoil assemblies 108, 110 are configured to break in a controlled manner upon impact with water. For instance, in some examples, a joint between the main hydrofoil strut 132 and the hull 102 and/or a joint between the rear hydrofoil strut 138 and the hull 102 is 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. f. Battery system
• FIG. 4 illustrates an example of an onboard battery system.
• the battery system 400 is arranged in a protected area 402 of the hull 102 below a passenger seating area 404. Some examples of the battery system 400 are separated from the passenger seating area 404 by a firewall 406 to protect the passengers from harm if a thermal runaway occurs.
• some examples of the craft 100 include a battery management system comprising voltage, current, and/or thermal sensors for detecting thermal runaway or some other fire detection system for detecting a fire in the protected area 402.
• Some examples of the craft 100 include one or more mechanisms for flooding the battery system 400 (e.g., with an inert gas fire, with water, etc.) upon detecting a thermal runaway or a fire in the protected area 402.
• some examples of the hull 102 comprise one or more valves or other controllable openings.
• the control system of the craft 100 is configured to open the valves and/or controllable openings upon detecting a fire in the protected area 402 or thermal runaway in the battery system 400 to allow water to enter the protected area 402 and to extinguish or prevent a fire in the protected area 402.
• the battery system 400 is configured to be jettisoned through one or more of the controllable openings in the hull 102 described above.
• the weight of the battery system 400 is sufficient to jettison the battery system 400 out of the hull 102 when the hull 102 is opened.
• the craft 100 comprises an actuator or the like configured to jettison the battery system 400 out of the hull 102.
• the craft 100 may take measures to become waterborne in response to detecting a fire in the protected area 402 or thermal runaway in the battery system 400.
• Some examples of the control system of the craft 100 determine a fire suppression operation to perform based on the operational state of the craft 100 (e.g., operating in hull-borne, hydrofoil-borne, or wing-borne mode). For instance, when operating in hull-borne mode and upon detecting a thermal runaway or a fire in the protected area 402, some examples of the control system are configured to flood the battery system 400 as described above.
• control system When operating in hydrofoil- borne or a wing-borne mode, the control system is configured to cause the craft 100 to transition to hull-borne mode upon detecting a thermal runaway or a fire in the protected area 402 and then flood the battery system 400.
• FIG. 5 illustrates an example of a control system 500 of the craft 100.
• control system 500 include one or more processors 502, data storage 504, a communication interface 506, a propulsion system 508, actuators 510, a Global Navigation Satellite System (GNSS) 512, an inertial navigation system (INS) 514, a radar system 516, a lidar system 518, an imaging system 520, various sensors 522, a flight instrument system 524, and flight controls 526.
• GNSS Global Navigation Satellite System
• INS inertial navigation system
• radar system 516 e.g., a radar system 516
• lidar system 518 e.g., a radar system 516
• an imaging system 520 e.g., various sensors 522, a flight instrument system 524, and flight controls 526.
• communication links 528 e.g., a system bus, a public, private, or hybrid cloud communication network, etc.
• processors 502 correspond to or comprise 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.
• 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
• processors 502 are illustrated as a separate stand-alone component of the control system 500, it should also be understood that the one or more processors 502 could comprise processing components that are distributed across one or more of the other components of the control system 500.
• the data storage 504 comprise one or more non-transitory computer-readable storage mediums that are collectively configured to store (i) program instructions executable by the one or more processors 502 such that the control system 500 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 500 in connection with the functions disclosed herein.
• the one or more non-transitory computer-readable storage mediums of data storage 504 may take various forms, examples of which may include volatile storage mediums such as random-access memory, registers, cache, etc.
• non-volatile storage mediums such as read-only memory, a hard-disk drive, a solid-state drive, flash memory, an optical-storage device, etc.
• data storage 504 is illustrated as a separate stand-alone component of the control system 500, it should also be understood that the data storage 504 may comprise computer-readable storage mediums that are distributed across one or more of the other components of the control system 500.
• the communication interface 506 include one or more wireless interfaces and/or one or more wireline interfaces, which allow the control system 500 to communicate via one or more networks.
• Some example wireless interfaces provide for communication under one or more wireless communication protocols, such as Bluetooth, WiFi (e.g., an IEEE 802.11 protocol), Long-Term Evolution (LTE), WiMAX (e.g., an IEEE 802.16 standard), a radio-frequency ID (RFID) protocol, near-field communication (NFC), and/or other wireless communication protocols.
• wireless communication protocols such as Bluetooth, WiFi (e.g., an IEEE 802.11 protocol), Long-Term Evolution (LTE), WiMAX (e.g., an IEEE 802.16 standard), a radio-frequency ID (RFID) protocol, near-field communication (NFC), and/or other wireless communication protocols.
• RFID radio-frequency ID
• NFC near-field communication
• wireline interfaces include an Ethernet interface, a Universal Serial Bus (USB) interface, CAN Bus, RS-485, 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.
• USB Universal Serial Bus
• RS-485 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.
• Some examples of the propulsion system 508 include one or more electronic speed controllers (ESCs) for controlling the electric motor propeller assemblies 116 distributed across the main wing 104 and, in some examples, across the horizontal stabilizer 124. Some examples of the propulsion system 508 include a separate ESC for each respective propeller assembly 116, such that the control system 500 individually controls the rotational speeds of the electric motor propeller assemblies 116.
• ESCs electronic speed controllers
• the actuators 510 include any of the actuators described herein, including (i) actuators for raising and lowering the flaps 118, ailerons 120, elevators 126, main hydrofoil control surfaces 134, and rear hydrofoil control surfaces 140, (ii) actuators for turning the rudder 128, the main hydrofoil control surfaces 134 positioned on the main hydrofoil strut 132, and the rear hydrofoil control surfaces 140 positioned on the rear hydrofoil strut 138, (iii) actuators for retracting and extending the main hydrofoil assembly 108 and the rear hydrofoil assembly 110, and/or (iv) actuators for performing the various other disclosed actuations of the main hydrofoil assembly 108 and the rear hydrofoil assembly 110.
• Each of the actuators described herein may include any actuators now known or later developed capable of performing the disclosed actuation.
• Some examples of the actuators correspond to linear actuators, rotary actuators, hydraulic actuators, pneumatic actuators, electric actuators, electro-hydraulic actuators, and mechanical actuators.
• Some examples of the actuators correspond to electric motors, stepper motors, and hydraulic cylinders. Other examples are contemplated herein as well.
• Some examples of the GNSS system 512 are configured to provide a measurement of the location, speed, altitude, and heading of the craft 100.
• the GNSS system 512 includes one or more radio antennas paired with signal processing equipment. Data from the GNSS system 512 may allow the control system 500 to estimate the position and speed of the craft 100 in a global reference frame, which can be used for route planning, operational envelope protection, and vehicle traffic deconfliction by both understanding where the craft 100 is located and comparing the location with known traffic.
• Some examples of the INS 514 include motion sensors, such as angular and/or linear accelerometers, and rotational sensors, such as gyroscopes, to calculate the position, orientation, and speed of the craft 100 using dead reckoning techniques. In some examples, one or more of these components are used by the control system to calculate actuator outputs to stabilize or otherwise control the vehicle during all modes of operation.
• motion sensors such as angular and/or linear accelerometers
• rotational sensors such as gyroscopes
• the radar system 516 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 516 processes the received radio waves to determine information about the object’s location and speed relative to the craft 100.
• This radar system 516 may be utilized to detect, for example, the water surface, maritime or wing-borne vehicle traffic, wildlife, or weather.
• the lidar system 518 comprise 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 518 measures the time for the reflected light to return to the receiver to determine the distance between the craft 100 and the object.
• This lidar system 518 may be utilized by the flight control system to measure the distance from the craft 100 to the surface of the water in various spatial measurements.
• Some examples of the imaging system 520 include one or more still and/or video cameras configured to capture image data from the environment of the craft 100. Some examples of the cameras correspond to or comprise 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. Some examples of the imaging system 520 are configured to perform 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.
• CCD charge-coupled device
• CMOS complementary metal -oxide-semiconductor
• SWIR short-wave infrared
• MWIR mid-wave infrared
• LWIR long-wave infrared
• Some examples of the imaging system 520 are configured to perform obstacle avoidance, localization techniques, water surface tracking for
• control system 500 include various other sensors 522 for use in controlling the craft 100.
• sensors 522 correspond to or comprise thermal sensors or other fire detection sensors for detecting a fire in the hull 102 or for detecting thermal runaway in the battery system 400.
• the sensors 522 may include position sensors for sensing the position of the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 (e.g., sensing whether the assemblies are in a retracted or extended position).
• 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.
• the sensors 522 facilitate determining the altitude of the craft 100.
• the sensor 522 include an ultrasonic altimeter configured to emit and receive ultrasonic waves. The emitted ultrasonic waves reflect off the water surface below the craft 100 and return to the altimeter. The ultrasonic altimeter measures the time for the reflected ultrasonic wave to return to the altimeter to determine the distance between the craft 100 and the water surface.
• Some examples of the sensor 522 include a barometer for use as a pressure altimeter. The barometer measures the atmospheric pressure in the environment of the craft 100 and determines the altitude of the craft 100 based on the measured pressure.
• Some examples of the sensor 522 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 craft 100 to determine a distance between the craft 100 and the water surface.
• these sensors are placed in different locations on the craft 100 to reduce the impact of sensor constraints, such as sensor deadband or sensitivity to splashing water.
• control system 500 are configured to use one or more of the sensors 522 or other components of the control system 500 to help navigate the craft 100 through maritime traffic or to avoid any other type of obstacle. For example, some examples of the control system 500 determine the position, orientation, and speed of the craft 100 based on data from the INS 514 and/or the GNSS 512, and the control system 500 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 516, the lidar system 518, and/or the imaging system 520. Some examples of the control system 500 determine the location of an obstacle using the Automatic Identification System (AIS). Some examples of the control system 500 are configured to maneuver the craft 100 to avoid collision with an obstacle based on the determined position, orientation, and speed of the craft 100 and the determined location of the obstacle by actuating various control surfaces of the craft 100 in any of the manners described herein.
• AIS Automatic Identification System
• flight instrument system 524 includes instruments for providing data about the altitude, speed, heading, orientation (e.g., yaw, pitch, and roll), battery levels, or any other information provided by the various other components of the control system 500.
• flight controls 526 include one or more joysticks, thrust control levers, buttons, switches, dials, levers, or touch screen displays, etc. In operation, a pilot may use the flight controls 526 to operate one or more control surfaces (e.g., flaps, ailerons, elevators, rudder, propulsion propellers, etc.) of the craft 100 to thereby maneuver the craft 100 (e.g., control the direction, speed, altitude, etc., of the craft 100)
• control surfaces e.g., flaps, ailerons, elevators, rudder, propulsion propellers, etc.
• the combinations of control surfaces on the craft 100 used by the control system 500 to control operations of the craft 100 depends on the mode of operation of the craft 100 and is determined based at least in part on aspects such as vehicle position, speed, attitude, acceleration, rotational rates, and/or altitude above water.
• Table 1 summarizes an example of the relationship between the control surfaces and the operation mode.
• the propulsion control surfaces in the table include the propeller assembly 116, as well as any propellers mounted to the hull 102, main hydrofoil assembly 108, or rear hydrofoil assembly 110.
• the aerodynamic elevator control surfaces include elevator 126
• the aerodynamic ailerons include ailerons 120
• the aerodynamic rudder includes rudder 128 (when not submerged)
• the aerodynamic flaps include flaps 118
• the hydrodynamic elevator includes rear hydrofoil control surfaces 140
• the hydrodynamic flaps include main hydrofoil control surfaces 134
• the hydrodynamic rudder includes rudder 128 (when submerged).
• control system 500 when actuating the control surfaces in the various examples, operational modes identified in Table 1 above, the control system 500 executes different levels of stabilization along the various vehicle axes during different modes of operation.
• Table 2 below identifies examples of stabilization controls that the control system 500 applies during the various modes of operation for each axis of the craft 100.
• Closed-loop control may comprise feedback and/or feed-forward control.
• control system 500 is configured to actuate different control surfaces to control the movement of the craft 100 about its different axes.
• Table 3 below identifies example axial motions that are affected by the various control surfaces of the craft 100.
• FIG. 6A illustrates an example of the craft 100 when the craft 100 is operating in a hull-borne mode.
• the craft 100 is docked and floating on the hull 102, with the buoyancy of the outriggers 114 providing for roll stabilization of the craft 100.
• the battery system 400 of the craft 100 may be charged.
• rapid charging is aided by an open or closed-loop water-based cooling system.
• the surrounding body of water is used in the loop or as a heat sink.
• the craft 100 includes a heat sink integrated into the hull 102 for exchanging heat from the battery system 400 to the surrounding body of water.
• the heat sink is located offboard in order to reduce the mass of the craft 100.
• the propeller assemblies 116 are folded in a direction away from the dock while the craft 100 is docked 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, in some examples, the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 are retracted (or partially retracted) to avoid collisions with nearby underwater structures.
• the craft 100 uses its propulsion systems, including the propeller assemblies 116 and/or the underwater propulsion system (e.g., one or more propellers mounted to the hull 102, the main hydrofoil 130, and/or the rear hydrofoil 136), to maneuver away from the dock while remaining hull-borne.
• the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 remain retracted (or partially retracted) during this maneuvering to reduce the risk of hitting underwater obstacles near docks or in shallow waterways.
• the craft 100 may partially or fully extend the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110. With the main hydrofoil assembly 108 and/or the rear hydrofoil assembly 110 extended, the craft 100 actuates the main hydrofoil control surfaces 134 and/or the rear hydrofoil control surfaces 140 to improve maneuverability as described above.
• the control system 500 controls the position and/or rotation of the craft 100 by causing all of the propeller assemblies 116 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 instance, in some examples, the control system 500 causes propeller assemblies 116a, 116c, 116e, 116h, 116j, and 1161 to idle in reverse and propeller assemblies 116b, 116d, 116f, 116g, 116i, and 1161 to idle forward. In this arrangement, the control system 500 causes the craft 100 to make various maneuvers without having to change the direction of rotation of any of the propeller assemblies 116.
• the control system 500 increases the speed of the reverse propeller assemblies on one side of the main wing 104 while increasing the speed of the forward propeller assemblies on the other side of the main wing 104 and without causing any of the propeller assemblies to transition from forward to reverse or from reverse to forward.
• idling the propellers at a nominal RPM may allow for a faster response in generating a yaw moment on the craft 100 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.
• FIG. 6B illustrates an example of the craft 100 when the craft 100 is operating in hydrofoil-borne maneuvering mode.
• the craft 100 is configured to, for example, move through harbors and crowded waterways at speeds generally between 20-45 mph.
• the craft 100 may extend the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 (if not already extended) and accelerate using the previously described propulsion system towards a desired takeoff speed.
• the craft 100 reaches a speed at which the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 alone support the weight of the craft 100, and the hull 102 is lifted above the surface of the water (e.g., by 3-5 ft) so that the hull is clear of any surface waves.
• the control system 500 reduces the speed of the propeller assemblies 116 to lower the thrust of the craft 100.
• control system 500 sustain this operational mode by actively controlling the pitch and speed of the craft 100 so that the main hydrofoil assembly 108 and the rear hydrofoil assembly 110 continue to entirely support the weight of the craft 100.
• control system 500 actuate the main hydrofoil control surfaces 134 and/or the rear hydrofoil control surfaces 140 and/or the propulsion system to stabilize the attitude of the craft 100 to maintain the desired height above the surface of the water, vehicle heading, and vehicle forward speed.
• control system 500 are configured to detect various changes in the yaw, pitch, or roll of the craft 100 based on data provided by the INS 514 and to make calculated actuations of the main hydrofoil control surfaces 134 and/or the rear hydrofoil control surfaces 140 to counteract the detected changes.
• Figure 7A illustrates an example of the craft 100 when the craft 100 is operating in hydrofoil -borne takeoff mode.
• the craft 100 is configured to, for example, move through open waters and obtain speeds generally between 40-50 mph to facilitate generating the lift required to become wing-borne.
• aero lift generally represents the lift generated by the main wing 104 of the craft 100 but can also include the lift generated by other surfaces such as the tail wing, hull, or propulsive devices such as propellers, rotors, jets, etc.
• LF generally corresponds to the lift generated by one or more hydrofoils 130, 136 of the craft 100, where LFF corresponds to the lift generated by the front foil and the LFR corresponds to the lift generated by the rear foil.
• WCRAFT corresponds to the force of gravity exerted on the craft 100 and is also referred to as the weight of the craft.
• WCRAFT generally corresponds to LW+LFR+LFF which also corresponds to LNET.
• the term LF is generally understood to correspond to LFR+LFF.
• the vehicle will accelerate upwards and potentially create a premature takeoff condition (prior to condition CO in Figure 7B) as the aero lift, LW, generated by the wings, etc., of the craft 100 would be insufficient to sustain flight, and, as a result, the craft 100 would come back down and breach the water, ultimately preventing takeoff.
• the techniques disclosed below ameliorate these problems by controlling the hydrofoil lift vector, LF, specifically by generating downward forces of one or more hydrofoils 130, 136 of the craft 100 to keep the hydrofoils 130, 136 submerged until after the upwards aero lift, LW, is sufficient to allow the craft 100 to sustain flight.
• the lift LF is in the downward direction, and is introduced via the hydrofoil(s) as LW increases beyond WCRAFT while the craft 100 is increasing in speed in anticipation of takeoff. This allows the craft 100 to generate a greater overall aero lift, LW, prior to actual takeoff than would otherwise be possible. Then, at the appropriate time (e.g., when LW reaches some predetermined threshold such as the weight of the craft 100 or some margin thereof), the negative lift, LF, can be “released” from the craft 100, and the craft 100 can, as a result, proceed to become wing-borne.
• some predetermined threshold such as the weight of the craft 100 or some margin thereof
• FIG. 7B is an example of a graph 700 that relates these aspects.
• the relationships shown in the graph 700 and the ways in which various lift forces, thresholds, etc., are depicted are merely examples and are provided to aid understanding of the various operations and procedures described herein.
• the speed of the craft 100 is such that LNET is sufficient to allow the craft 100 to operate in hydrofoil-borne maneuvering mode but is insufficient to allow the craft 100 to become wing-borne.
• LW increases with increased craft 100 water speed.
• LF is reduced in proportion to an increase in LW. For example, LF is adjusted with the speed of the craft 100 to maintain LNET at a margin equal to the weight, WCRAFT, of the craft 100, or small deviations about equal to control ride height..
• the overall lift provided by the hydrofoils 130, 136 may decrease at the same rate at which lift from the wing is increased towards zero or even become negative with increased speed. For example, just before the speed of the craft 100 reaches the speed associated with condition CO, LF may be reduced to zero.
• the conditions at CO e.g., speed of the craft 100, angle of attack of craft 100, deflection angles of control surfaces, angle of incidence of hydrofoils, etc.
• LF may be gradually or abruptly removed/released. This, in turn, allows LNET to approximately equal to or greater than WCRAFT which allows the craft 100 to take off and become wing-borne.
• LF is not removed/released as described. Rather, as the craft 100 continues to accelerate, the downwards hydrofoil lift, LF, increases to a maximum downwards amount (e.g., a predetermined maximum amount and/or a maximum amount achievable due to the limitations of the control capabilities of the hydrofoil). As the aero lift, LW, generated by the main wing 105 continues to increase past this maximum amount of downwards hydrofoil lift, LF, LNET increases in the upwards direction beyond WCRAFT and the craft 100 is pulled from the water. This, in turn transitions the craft 100 to a wing-borne mode of operation. d. Wing-Borne Operation
• FIG. 8 illustrates an example of the craft 100 after becoming wing borne.
• the control system 500 causes the main hydrofoil deployment system 200 and the rear hydrofoil deployment system 300 to respectively retract the main hydrofoil assembly 108 and the rear hydrofoil assembly 110.
• the control system 500 initiates this retraction as soon as the hydrofoil assemblies 108, 110 are clear of the water to reduce the chance of the hydrofoil assemblies 108, 110 reentering the water.
• the control system 500 may determine that the hydrofoil assemblies 108, 110 are clear of the water in various ways.
• the control system 500 makes such a determination based on a measured altitude of the craft 100 (e.g., based on data provided by the radar system 516, the lidar system 518, and/or the other sensors 522 described above for measuring an altitude of the craft 100).
• the sensors 522 may further include one or more conductivity sensors, temperature sensors, pressure sensors, strain gauge sensors, or load cell sensors arranged on the hydrofoil assemblies 108, 110, and the control system 500 may determine that the hydrofoil assemblies 108, 110 are clear of the water-based on data from these sensors.
• the control system 500 continues to accelerate the craft 100 to the desired cruise speed by controlling the speed of the propeller systems 116.
• the control system 500 retracts the flap systems when the craft 100 has achieved sufficient airspeed to generate enough lift to sustain altitude without them and actuates various control surfaces of the craft 100 and/or applies differential thrust to the propeller systems 116 to perform any desired maneuvers, such as turning, climbing, or descending, and to provide efficient lift distribution.
• the craft 100 can fly both low over the water’s surface in ground-effect or above ground-effect depending on operational conditions and considerations. e. Return to Hull-Borne Operation
• the control system 500 determines that the hydrofoil assemblies 108, 110 are fully or partially retracted so that the craft 100 may safely land on its hull 102. In some examples, the control system 500 additionally determines and suggests the desired landing direction and/or location-based on observed, estimated, or expected water surface conditions (e.g., based on data from the radar system 516, the lidar system 518, the imaging system 520, or other sensors 522). [0136] The control system 500 initiates deceleration of the craft 100, for instance, by reducing the speeds of the propeller systems 116 until the craft 100 reaches a desired landing airspeed.
• the control system 500 may deploy the flaps 118 to increase lift at low airspeeds and/or to reduce the stall speed.
• the control system 500 reduces the descent rate (e.g., to be less than approximately 200 ft/min).
• the control system 500 further slows the descent rate to cushion the landing (e.g., to be less than approximately 50 ft/min).
• the control system 500 reduces thrust, and the craft 100 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 102 settles into the water as the speed is further reduced until the craft 100 is stationary.
• the craft 100 is transitioned back to hydrofoil-borne maneuvering mode (See Figure 6B) by extending the hydrofoil assemblies 108, 110 to transition from hull-borne operation to hydrofoil-borne operation in the same manner as described above.
• the control system 500 then sustains the hydrofoil-borne mode at the fifth stage and maneuvers the craft 100 into port while keeping the hull 102 insulated from surface waves.
• the control system 500 then reduces the thrust generated by the propeller assemblies 116 to lower the speed of the craft 100 until the hull 102 settles into the water, thereby transitioning that craft back to hull-borne operation at the sixth stage.
• the control system 500 then retracts the hydrofoil assemblies 108, 110 and performs the hull-borne operations described above to maneuver the craft 100 into a dock for disembarking passengers or goods and recharging the battery system 400.
• the reduction in power to all of the propellers 116 can lead to a sudden loss of lift and, therefore, altitude, which can be an especially relevant consideration for craft 100, such as those disclosed herein, that fly just above the water. Losing lift, and/or increasing the pitch of the craft 100 suddenly in an attempt to counteract an anticipated loss of lift can lead to passenger discomfort, which is an important consideration for commercial implementations.
• Some examples of the craft 100 disclosed herein address these aspects by selectively controlling the rotation rate of particular propeller(s) in a way that either induces or reduces drag on the craft 100 without substantially effecting the amount of lift on the craft 100. More specifically, drag is induced or reduced on the craft 100 by reducing or increasing, respectively, the relative rotation rate of a first subset of propellers 116 (i.e., relative to the rotation rate of other propellers). Lift on the craft 100 is maintained by maintaining (or increasing) the relative rotation rate of a second subset of propellers 116.
• the first subset of propellers 116 correspond to those propellers 116 that are less critical to the control of the craft 100.
• the first subset of propellers 116 may include those propellers 116 that are positioned on one or more sections of the main wing 104 of the craft 100 that contribute relatively less, or that contribute the least amount of lift and/or roll on the craft 100 when air is blown over the sections.
• these propellers 116 correspond to the propellers 116 that are positioned nearest to the hull.
• the first subset of propellers 116 may include propellers 116g and 116f and/or propellers 116h and 116e.
• propellers 116 of the first subset of propellers 116 may be symmetrically positioned on the port side section and the starboard side section of the main wing 104 to help cancel any roll moment that may otherwise be induced when the respective rotation rates of these propellers 116 is reduced.
• the propellers 116 have the same relative distance from the hull.
• the second subset of propellers 116 correspond to those propellers 116 that are more critical to the control of the craft 100.
• the second subset of propellers 116 may include those propellers 116 positioned on one or more sections of the main wing 104 of the craft 100 that contribute relatively more, or that contribute the most amount of lift and/or roll on the craft 100 when air is blown over the sections.
• these propellers 116 correspond to the rest of the propellers 116 (i.e., the propellers 116 that do not belong to the first subset of propellers) and/or the propellers 116 that are positioned furthest from the hull.
• the second subset of propellers 116 may include propellers 116a-l 16d and 116i- 1161.
• the propellers 116 of the second subset of propellers 116 may be symmetrically positioned on the port side section and the starboard side section of the main wing 104 to help cancel any roll moment that may otherwise be induced when the respective rotation rates of these propellers 116 is adjusted.
• the propellers 116 that are more critical to the control of the craft 100 correspond to those propellers 116 that are positioned forward of sections of the wings that contribute meaningfully to roll control and/or lift on the craft 100, such as positions forward of the ailerons.
• those correspond to propellers 116a and 1161.
• the ailerons may be positioned along different sections of the wing, the ailerons may span a greater length of the wing, and/or there may be multiple ailerons on each wing section. Propellers positioned forward of any such ailerons may be grouped within the second subset of propellers 116.
• propellers 116 that are less critical to the control of the craft 100 correspond to those propellers 116 that are positioned forward of sections of the wings that do not contribute meaningfully to roll control and/or lift on the craft 100.
• some examples of these propellers may be positioned forward of the flaps.
• those correspond to propellers 116e - 116h.
• the propellers 116 that are less critical to the control of the craft 100 have to be positioned nearest to the hull and that the propellers 116 that are most critical to the control of the craft 100 have to be positioned furthest from the hull.
• the geometry of the main wing 104 can be configured so that there are sections further from the hull that do not contribute meaningfully to control of the craft 100, and there are sections nearer to the hull that do contribute meaningfully to control of the craft 100.
• propellers 116 forward of these sections may or may not be critical to the control of the craft 100 depending on the configuration of the main wing 104.
• the first subset of propellers and the second subset of propellers, in the examples described herein, may be any suitable respective subset of the propellers of the craft a. Airspeed Control Logic
• Figure 9 illustrates an example of airspeed control logic 900 that is implemented by an example of the control system 500 of the craft 100 to control the airspeed of the craft 100.
• the airspeed control logic 900 is implemented via instruction code that is executed by one or more processors of the control system 500 that causes the control system 500 to implement the airspeed control logic 900.
• one or more of the aspects of the airspeed control logic 900 can be implemented in dedicated hardware such as via one or more application-specific integrated circuits (ASICs).
• ASICs application-specific integrated circuits
• the airspeed control logic 900 is performed automatically, for example, in response to changes in various input signals. These aspects are described in more detail below.
• one or more aspects of the airspeed control logic 900 can be performed manually by and/or based on information received from, for example, the pilot of the craft 100.
• the airspeed control logic 900 includes target RPM determination logic 905, airspeed error logic 910, first RPM signal generation logic 915, and second RPM signal generation logic 920. Some examples of the airspeed control logic 900 receive a target airspeed indication 902 and a craft airspeed indication 904, and output a first propeller RPM control signal 926 and a second propeller RPM control signal 928 that control the rotation rate of the propellers 116 of the craft 100. Some examples of the craft airspeed indication 904 are representative of the actual real-time airspeed of the craft 100 and are determined (e.g., by the control system 500) based on one or more airspeed sensors of the craft 100.
• an airbrake control may be provided to allow the pilot of the craft 100 to temporally induce drag on the craft 100.
• Airbrake control logic e.g., airbrake instruction code executed by one or more processors of the control system 500
• the airspeed control logic 900 may, in turn, control the airspeed of the craft 100 to match the indicated target airspeed indicated by the airbrake control logic.
• Some examples of the target RPM determination logic 905 receive the target airspeed indication 902 and are configured to output an RPM value that is determined to be associated with a particular target airspeed.
• This RPM value generally corresponds to an initial estimate of where the rotation rate of all the propellers 116 should eventually reach so that the craft 100 will attain a desired airspeed.
• the actual rate at which the propellers 116 rotate may be adjusted to an extent based on other considerations (e.g., based on the actual observed airspeed of the craft, among other observed characteristics and/or desired control outcomes).
• the target RPM determination logic 905 include a lookup table that associates different target airspeeds with different RPM values.
• An example of the lookup table may be stored in data storage 504 of the control system 500.
• each RPM value is an estimated value that should be applied to all of the propellers 116 of the craft 100 to allow the craft 100 to travel at an associated airspeed or at a speed that is approximately equal to the associated airspeed.
• the RPM values for one or more associated target airspeeds are adjusted (e.g., in real-time) based on the operating environment of the craft 100. For example, the RPM values may be adjusted to compensate for different air densities, temperatures, etc.
• the RPM values may be adjusted based on the weight of the craft 100 (e.g., based on the number of passengers, amount of cargo, etc.)
• the target RPM value is determined as a function (e.g., linear or non-linear function) of the target airspeed and/or the target airspeed and other operating parameters of the craft 100, such as the air temperature, air density, air temperature, the weight of the craft, etc.
• Some examples of the airspeed error logic 910 receive the target airspeed indication 902 and the craft airspeed indication 904 and output a value that is proportional to the difference between the target airspeed and the craft airspeed. For example, when the difference between the target airspeed and the craft airspeed is zero, the value output by the airspeed error logic 910 may be zero (or otherwise representative of “zero” or “no” error between the actual craft airspeed and the target airspeed). When the target airspeed is greater than the craft airspeed, a negative value may be output by the airspeed error logic 910, and when the target airspeed is lower than the craft airspeed, a positive value may be output by the airspeed error logic 910 or vice versa.
• the second RPM signal generation logic 920 receive the respective outputs of the target RPM determination logic 905 and the airspeed error logic 910 and output the second propeller RPM control signal 928.
• the second propeller RPM control signal 928 controls or influences the rotation rate of one or more propellers 116.
• the second propeller RPM control signal 928 may be an analog or digital signal communicated to power electronics of the motors of the propellers 116 that controls the amount of torque delivered by the motors to the propellers 116.
• the second propeller RPM control signal 928 can cause the power electronics to switch, at least momentarily or in a pulsed manner, the direction of the torque applied to the propellers 116 to rapidly lower the rotation rate of the propellers 116.
• the torque reversal technique may be applied until the propellers 116 reach a desired rotation rate.
• the motors may include one or more sensors (e.g., hall effect sensors, optical sensors, etc.) that facilitate determining the actual rate of rotation of the motor.
• some examples of the second RPM signal generation logic 920 may receive an indication of the actual rotation rate of each propeller and adjust the power to each motor to cause the rotation rate of each propeller to match a particular target rotation rate.
• the second propeller RPM control signal 928 is communicated to the second subset of propellers 116 (i.e., in some examples, those propellers 116 that are more critical to the control of the craft 100).
• the second RPM signal generation logic 920 may control the second subset of propellers 116 to rotate at the target rate that is output by the target RPM determination logic 905 because there would be no further adjustment to the target RPM provided to the second RPM signal generation logic 920.
• the second RPM signal generation logic 920 may control the second subset of propellers 116 to gradually change to a rotation rate that corresponds to the target rotation rate adjusted corresponding to a value that is proportional to the absolute value of the difference of the target airspeed and the craft airspeed.
• the second RPM signal generation logic 920 may control the second subset of propellers 116 to gradually change to a rotation rate that corresponds to the target rotation rate adjusted corresponding to a value that is proportional to the absolute value of the difference of the target airspeed and the craft airspeed. The gradual change in the rotation rate prevents a sudden loss of lift on the craft 100 from occurring.
• the second RPM signal generation logic 920 can control each propeller 116 of the second subset of propellers 116 to rotate at somewhat different rates according to the operations described above and there may be slightly different target RPM values specified by the target RPM determination logic 905 for each propeller 116. Such an approach may enable the system to “finely” control the rate of change of the speed of the craft overall.
• all the propellers of the second subset of the propellers, and for that matter the first subset of the propellers may rotate in the same or opposite direction.
• one or more symmetrically arranged pairs of propellers on both sides of the craft 100 may rotate in opposite directions to limit or minimize roll in the craft 100 and may rotate in the same direction to induce roll into the craft 100.
• the relative rotation directions can change during flight to, for example, induce the craft 100 to roll in a first direction towards a particular orientation during a first interval and then to roll the craft 100 back to its original orientation or yet another orientation.
• the first propeller RPM signal generation logic 915 receive the output of the airspeed error logic 910, the output of the second propeller RPM generation logic 920, and an RPM delta limit indication 930, and output the first propeller RPM control signal 928.
• the first propeller RPM control signal 926 is communicated to the first subset of propellers 116 (i.e., in some examples, those propellers 116 that are less critical to the control of the craft 100), and controls or influences the rotation rate of the first subset of propellers 116 in a manner similar in some respects to the way in which the second propeller RPM control signal 928 controls the rotation rate of the second subset of propellers 116.
• the first propeller RPM signal generation logic 920 may control the first subset of propellers 116 to rapidly decrease their respective rotation rates. And in some examples, when the output of the airspeed error logic 910 indicates that the craft airspeed is below the target airspeed, the first propeller RPM signal generation logic 920 may control the first subset of propellers 116 to rapidly increase their respective rotation rates.
• the first propeller RPM signal generation logic 920 is configured to slew limit the rate at which the rotation is changed according to the RPM delta limit indication 930.
• the RPM delta limit indication 930 may indicate an RPM delta value of 10 RPM per second. This may cause the first RPM signal generation logic 915 to limit the rate of change in the rotation of the first subset of propellers 116 to 10 RPM per second.
• the propellers 116 of the first subset of propellers 116 do not necessarily have to rotate at the same rate.
• some examples of the first RPM signal generation logic 915 can control each propeller 116 of the first subset of propellers 116 to rotate at somewhat different rates. This aspect is described in more detail below.
• the craft 100 may include one or more “constant speed” propellers 116 that have variable pitch propellers that are adjusted to control the amount of thrust delivered by the propellers.
• the airspeed control logic 900 can control the pitch of one or more propellers 116 (e.g., pairs of symmetrically positioned propellers 116) to induce drag or to generate thrust to thereby control the overall airspeed of the craft 100.
• the rotation rate of such propellers 116 is conventionally considered to be relatively constant, the rotation rate may, in some circumstances, be adjusted to an extent by adjusting the power to propellers 116.
• the amount of drag induced by the propellers 116 may be adjusted by changing the pitch of the propellers 116 in combination with adjusting the power input to the propellers 116 to fine-tune the amount of drag induced by the propellers 116. For example, drag can be induced or increased by bringing the propellers forward to a flat pitch position so that the propellers are parallel to the main wing 104, thus increasing the rotation rate of the propellers 116 even while the power to the propeller motor is maintained or reduced.
• the pitch of the propellers relative to the main wing 104 may be brought back to a more perpendicular position relative to the main wing 104, which effectively reduces drag and increases power to the propellers 116.
• the airspeed control logic 900 may control the amount of pitch (or the amount by which the pitch should be adjusted) of the respective propellers 116 via the first propeller RPM control signal 926 and the second propellers RPM control signal 928 and/or via different control signals to the propellers 116.
• Figure 10 illustrates examples of operations 1000 that may be performed by the airspeed control logic 900 of the control system 500 that facilitate adjusting (i.e., increasing or decreasing) the airspeed of the craft 100 using the first subset of propellers 116.
• These operations are more clearly understood with reference to the profiles 1100, 1102 illustrated in Figure 11.
• the profiles in Figure 11 and the various steps described below more particularly describe reducing the airspeed of the craft 100 and then returning the airspeed of the craft 100 to its original airspeed.
• analogous operations can be performed to increase the airspeed of the craft 100 to some target airspeed and then to reduce the airspeed of the craft 100 to its original airspeed.
• the airspeed of the craft 100 doesn't necessarily have to be returned to its original airspeed.
• the airspeed can remain at the adjusted airspeed or can be adjusted to second, third, etc., different airspeeds in subsequent steps, (i.e., airspeeds that are different from the original airspeed).
• the craft 100 is initially cruising at a particular airspeed, and all the propellers 116a-l 161 of the craft 100 are rotating at a first rotation rate.
• the first rotation rate is different for one or more of the propellers 116a-l 161.
• some propellers 116 may rotate at 4500 RPM, some others may rotate at 5000 RPM, etc.
• the propellers 116a-l 161 rotate at the same or substantially the same rate (e.g., 5000 RPM). This mode of operation corresponds to the first interval 1105a of the first and second profiles 1100, 1102.
• this mode of operation is representative of the state of the craft 100 prior to the engagement of the airspeed control logic 900.
• the airspeed control logic 900 is engaged and during this interval, the first RPM signal generation logic 915 and the second RPM signal generation logic 920 may control the first subset of propellers 116 and the second subset of propellers 116, respectively, to rotate at the first rate.
• the operations at block 1010 involve receiving an indication to adjust the airspeed of the craft 100.
• the airspeed control logic 900 may receive an indication from the pilot or autopilot of the craft 100 to adjust the airspeed of the craft 100.
• the indication may specify a target airspeed to which the airspeed should be adjusted.
• the operations between block 1015 and block 1020 involve adjusting (e.g., reducing) the rotation rate of the first subset of the propellers 116 to an extent until the indication to adjust the rotation rate has been removed.
• an indication to reduce the rotation rate of the first subset of the propellers 116 may be received during the first interval 1105a and during the second interval 1105b, the rotation rate of the first subset of the propellers 116 is gradually reduced. Reduction in the rate at which these propellers 116 rotate will induce drag on the craft 100. The drag will, in turn, cause a gradual reduction in the airspeed of the craft 100.
• the rate at which the rotation is reduced is slew limited according to the RPM delta limit indication 930 that is input into the first RPM signal generation logic 915, as described above.
• the operations between blocks 1015 and 1020 may be performed in an iterative manner until the actual/ob served craft airspeed reaches the target airspeed.
• the craft 100 may include one or more “constant speed” propellers 116 that have variable pitch propellers that are adjusted to control the amount of drag induced by the propellers on the craft 100.
• the operations between blocks 1015 and 1020 for reducing the airspeed of the craft 100 may additionally, or alternatively, involve controlling the propeller pitch of one or more propellers 116 to induce drag on the craft 100 to reduce the airspeed of the craft 100.
• the operations between block 1025 and block 1030 are performed after the indication to adjust the airspeed is removed.
• the rotation rate of the first subset of propellers 116 is gradually increased back to the original rotation rate (i.e., the rotation rate associated with the first interval 1105a) and the airspeed of the craft 100 returns back to the original airspeed.
• the rate at which the rotation rate is increased (or decreased) is slew limited according to the RPM delta limit indication 930 that is input into the first RPM signal generation logic 915, as described above.
• the operations between blocks 1015 and 1020 may be performed in an iterative manner until the actual/ob served craft airspeed reaches the original airspeed.
• the operations between blocks 1025 and 1030 for increasing the airspeed of the craft 100 may additionally, or alternatively, involve controlling the prop pitch of one or more propellers 116 to reduce drag or increase thrust on the craft 100 to increase the airspeed of the craft 100.
• the operations between block 1015 and block 1020 may instead involve increasing the rotation rate of the first subset of the propellers 116 to an extent until the indication to increase the rotation rate has been removed.
• the operations between block 1025 and block 1030 may instead involve decreasing the rotation rate of the first subset of the propellers 116 gradually back to the original rotation rate (i.e., the rotation rate associated with the first interval 1105a) and so that the airspeed of the craft 100 returns back to the original airspeed.
• Figure 12 illustrates examples of operations 1200 that may be performed by the airspeed control logic 900 of the control system 500 that facilitate adjusting (i.e., increasing or decreasing) the airspeed of the craft 100 to a target airspeed using the first subset of propellers 116 and the second subset of propellers 116.
• These operations are more clearly understood with reference to the first and second profiles 1300, 1302, illustrated in Figure 13.
• the profiles in Figure 13 and the various steps described below more particularly describe reducing the airspeed of the craft 100.
• analogous operations can be performed to increase the airspeed of the craft 100 to some target airspeed
• the craft 100 is initially cruising at a particular airspeed, and all the propellers 116a-l 161 of the craft 100 are rotating at a first rotation rate.
• the first rotation rate is different for one or more of the propellers 116a-l 161.
• some propellers 116 may rotate at 4500 RPM, some others may rotate at 5000 RPM, etc.
• the propellers 116a- 1161 rotate at the same or substantially the same rate (e.g., 5000 RPM). This mode of operation is shown in the first interval 1305a of the first and second profiles 1300, 1302.
• this mode of operation is representative of the state of the craft 100 prior to the engagement 900 of the airspeed control logic 900.
• the airspeed control logic 900 is engaged.
• the first RPM signal generation logic 915 and the second propeller RPM signal generation logic 920 may control the first subset of propellers 116 and the second subset of propellers 116, respectively, to rotate at the first rate, which may be associated with a particular airspeed.
• the operations at block 1210 involve receiving an indication to adjust the airspeed of the craft 100 to a particular target airspeed. This is indicated at the beginning of the second interval 1305b of the first profile 1300.
• the airspeed control logic 900 may receive an indication from the pilot or autopilot of the craft 100 to adjust the airspeed of the craft 100 to a particular target airspeed.
• the operations at block 1215 involve adjusting (e.g., reducing) the rotation rate of the second subset of propellers 116 to adjust (e.g., lower) the airspeed of the craft 100, as indicated in the second profile 1302.
• the target RPM determination logic 905 may output a rotation rate previously determined to be associated with the target airspeed.
• the rate of rotation of the second subset of propellers 116 is gradually reduced towards the target rotation rate. Reducing the rotation rate of the second subset of propellers 116 may result in some loss of lift on the craft 100.
• the craft 100 may be pitched upward to an extent to compensate for at least some of the lost lift.
• the pitch of the craft 100 may be held within a desirable range to avoid passenger discomfort. While the second profile 1302 suggests that the reduction in the respective rotation rates of the first subset of propellers and the second subset of propellers occur simultaneously, this is not necessarily required. For example, the reduction in the rotation rate of the second subset of propellers may begin before or after the reduction in the rotation rate of the first subset of propellers.
• the operations at block 1220 involve adjusting (e.g., reducing) the rotation rate of the first subset of propellers 116 to a greater degree than that of the second subset of propellers 116 (e.g., reducing the rate to the indicated minimum rotation rate) as indicated in the second profile 1302.
• the first RPM signal generation logic 915 may output a first propeller RPM control signal 926 that causes the rotation rate of the first subset of propellers 116 to relatively rapidly reduce to a rate that is below that of the second subset of propellers 116.
• the rate at which the rotation is reduced may be slew limited according to the RPM delta limit indication 930 that is input into the first RPM signal generation logic 915, as described above. Reducing the rotation rate of the first subset of propellers 116 will induce drag on the craft 100. The drag will, in turn, cause a relatively rapid deceleration of the craft 100.
• the first RPM signal generation logic 915 determines the minimum rotation rate based in part on the difference between the current/ob served airspeed of the craft 100 and the target airspeed where lower rotation rates are commanded (i.e., more drag is induced) for greater differences between the current/ob served airspeed of the craft 100 and the target airspeed. In some examples, the first RPM signal generation logic 915 determines the minimum rotation rate based in part on the amount of time allotted to reduce the airspeed of the craft 100 with lower rotation rates being commanded (i.e., more drag being induced) for shorter allotted times.
• the first RPM signal generation logic 915 determines a quantity of propellers 116 to include in the first subset of propellers 116 based on the desired reduction of the airspeed of the craft 100 in the allotted time. For example, the number of propellers 116 for which the rotation rate may be increased to induce drag may be increased as more drag is required.
• the operations may repeat from block 1215.
• the rotation rate of the second subset of propellers 116 may continue to decrease gradually toward the target rotation rate.
• the rate of rotation of the first subset of propellers 116 may decrease, at least initially, towards the minimum rotation rate.
• the rate of rotation of the first subset of propellers 116 will gradually increase from the minimum rotation rate to the target rotation rate, e.g., until the airspeed error logic 910 indicates that the craft airspeed matches the target airspeed, as shown in block 1230.
• the craft 100 may include one or more “constant speed” propellers 116 that have variable pitch propellers that are adjusted to control the amount of drag induced by the propellers on the craft 100.
• the operations between blocks 1215 and 1225 for adjusting the airspeed of the craft 100 may additionally, or alternatively, involve controlling the prop pitch of one or more propellers 116 to induce drag on the craft 100 to reduce the airspeed of the craft 100, or decrease drag on the craft 100 to increase the airspeed of the craft 100.
• the craft 100 has reached the target airspeed, and the rotation rate of the first subset of propellers 116 and the second subset of propellers 116 are set to the same rotation rate as indicated in the third interval of the first and second profiles 1300, 1302 and as shown in block 1230.
• analogous operations can be performed, for example, to increase the airspeed of the craft 100 according to the techniques described above.
• the operations between block 1215 and block 1225 may instead involve increasing the respective rotation rates of the first subset of the propellers 116 and the second subset of the propellers 116 until the target airspeed is reached.
• the rotation rate of the second set of propellers may be gradually increased to a target rotation rate associated with the target airspeed.
• the rotation rate of the first set of propellers may be increased to a maximum rotation rate that is greater than the target rotation rate and then gradually reduced to the target rotation rate.
• the first subset of propellers 116 i.e., those used to induce drag on the craft, only include a single pair of propellers 116, one on each section of the main wing 104. This may be adequate for craft 100 that include twelve propellers 116, where there are six propellers 116 on each section of the main wing 104. Using only a single pair of propellers 116 as opposed to multiple pairs of propellers 116 generally means that less overall lift will be removed from the system.
• the rotation rates and/or pitches of the propellers 116 are adjusted/reduced in an equal/balanced manner so that the yaw, roll, etc. of the craft 100 does not change when performing the airspeed adjustments operation described herein.
• the respective rotation rates and/or pitches of pairs of symmetrically positioned propellers 116 are set to be about the same so that the amount of drag and/or thrust induced is balanced (e.g., to minimize yaw, roll, etc., when adjusting airspeed).
• these techniques are used to induce forces on the craft 100 to counteract or cause these effects.
• the rotation rate and/or pitch of one or more propellers 116 are intentionally controlled to be different to induce yaw, roll, etc. That is, the respective rotation rates and/or pitches of the propellers 116 can be made to be different to induce forces on the craft 100 that induce these effects.
• Such control over maneuverability may be performed in addition to or as an alternative to other techniques for causing or counteracting these effects (e.g., using control surfaces of the craft).
• the first subset of propellers 116 includes multiple pairs of propellers 116. Reducing the rotation rate of multiple pairs of propellers 116 facilitates lowering the airspeed of the craft 100 more quickly than would be possible using only a single pair of propellers 116.
• the number of propeller pairs in the first subset (that is, the number of propellers 116 that are “spun down”) is selected based on the desired craft deceleration rate. Increasing the number of pairs facilitates increasing the deceleration rate. Spinning down multiple propeller pairs may be more desirable as the total number of propellers 116 increases.
• the order in which the propeller pairs are selected is based on their respective distances from the hull, where the innermost pair of propellers 116 is selected first, followed by the next innermost pair of propellers 116, and so on.
• the amount by which the propeller pairs are spun down is based on their respective distances from the hull, where the innermost pair of propellers 116 are spun down by the greatest amount, the next innermost pair of propellers 116 is spun down to a lesser degree, and so on.
• the geometry of wing sections behind one or more propellers 116 that are not the closet to the hull are configured to be less critical to the control of the craft 100 so that stalling propellers 116 forward of these wing sections will not meaningfully impact control of the craft.
• Using such a main wing 104 configuration facilitates using or including propellers 116 in the first subset (i.e., those used to induce drag) that are not the closest to the hull.
• the diameter of the propellers 116 are different.
• the diameter of the propellers 116 that are positioned near sections of the main wing 104 that are less critical to the control of the craft 100 are larger than the diameter of the other propellers 116.
• the diameter of the innermost propellers 1 16 i.e., those that are spun down
• the innermost propellers 116 are forward of the flaps 118. Larger diameter propellers 116 are more efficient at blowing air over the flaps and can provide more thrust while the craft 100 is cruising.
• the geometry of the section of the main wing 104 that is behind these propellers 116 is optimized to facilitate the airspeed reductions described here (i.e., the geometry is configured so that the wing section does not contribute meaningfully to the lift on the craft 100.
• the inboard section of the main wing 104 were to have 4 degrees of incidence to 0 normally, then it may make sense to use 0 to 4 to 0 angle of incidence so that there is a lower angle inboard where the selected pair of propellers 116 is blowing. This would result in a loss of overall efficiency for the main wing 104 but may help avoid stalling on the inboard propellers 116.
• the rotation rate and/or the pitch of the propellers 116 is adjusted to induce drag on the craft 100 to reduce the airspeed of the craft 100 while minimizing any adverse effects on the lift on the craft 100.
• the rotation rate and/or the pitch of the propellers 116 may be returned to their respective original settings.
• analogous operations can be performed to increase the speed of the craft 100 while minimizing any adverse effects on the lift on the craft 100.
• the airspeed of the craft 100 can be increased by increasing the rotation rate and/or adjusting the pitch of the first subset of propellers 116 (i.e., those propellers 116 that are less critical to the control of the craft 100) while avoiding excess lift that would otherwise cause the craft 100 to climb in altitude, making the flight more comfortable for passengers.
• the pitch of the first subset of propellers 116 i.e., those propellers 116 that are less critical to the control of the craft 100
• the altitude of the craft 100 can be adjusted to an extent by using the techniques described herein without requiring any undesirable changes to the pitch of the craft 100.
• the rotation rate and/or the prop pitch of the second subset of propellers 116 i.e., those propellers 116 that are less critical to the control of the craft 100
• the rotation rate and/or the prop pitch of the second subset of propellers 116 can be adjusted to increase or decrease blown wing lift acting on the craft 100 to thereby adjust the altitude of the craft 100 to an extent.
• a craft comprising: (i) at least one hull; (ii) at least one wing coupled to the at least one hull, wherein the at least one wing comprises a port side section and a starboard side section; (iii) a blown wing propulsion system that comprises a plurality of propellers arranged along the port side section and the starboard side section of the at least one wing and configured to generate lift on the craft by blowing air over the at least one wing; and (iv) a control system configured to control a respective rotation rate of each propeller of the plurality of propellers.
• control system is configured to, after receiving an indication to reduce an airspeed of the craft, control the respective rotation rate of each propeller of a first subset of propellers from the plurality of propellers to be a first rotation rate that is lower than a second rotation rate at which each propeller of a second subset of propellers from the plurality of propellers rotate.
• Example 2 The craft according to example 1, wherein after controlling the respective rotation rate of each propeller of the first subset of propellers be the first rotation rate that is lower than the second rotation rate at which each propeller of a second subset of propellers rotates, lift on the craft remains substantially unchanged.
• Example 3 The craft according to any foregoing example(s), wherein for a particular rotation rate of each propeller in the plurality of propellers, an amount of thrust generated by the first subset of propellers is less than an amount of thrust generated by the second subset of propellers.
• Example 4 The craft according to any foregoing example(s), wherein for a particular rotation rate of each propeller in the plurality of propellers, an amount of control authority over the craft that results from a wake of air generated by the first subset of propellers over one or more control surfaces of the craft is less than an amount of control authority over the craft that results from a wake of air generated by the second subset of propellers.
• Example 5 The craft according to any foregoing example(s), wherein for a particular rotation rate of each propeller in the plurality of propellers, an amount of lift on the craft that results from a wake of air generated by the first subset of propellers over one or more control surfaces of the craft is less than an amount of lift on the craft that results from a wake of air generated by the second subset of propellers.
• the control system is configured to: maintain the rotation rate of the second subset of propellers.
• Example 7 The craft according to any foregoing example(s), wherein the first subset of propellers are positioned on one or more sections of the at least one wing that produce a least amount of lift when air is blown over the one or more sections of the at least one wing.
• Example 8 The craft according to any foregoing example(s), wherein at least some of the first subset of propellers are positioned forward of ailerons of the at least one wing, and wherein the first subset of propellers are positioned on one or more sections of the at least one wing that are furthest inboard or substantially away from the ailerons or otherwise least reduces a blowing effect over one or more roll-moment control surfaces of the at least one wing.
• Example 9 The craft according to any foregoing example(s), wherein at least some of the second subset of propellers are positioned forward of ailerons of the at least one wing, and the first subset of propellers are positioned forward of different sections of the at least one wing.
• Example 10 The craft according to any foregoing example(s), wherein the ailerons are positioned on outboard sections of the at least one wing.
• Example 11 The craft according to any foregoing exampl e(s), wherein the first subset of propellers correspond to propellers of the plurality of propellers that are positioned nearest to the at least one hull.
• Example 12 The craft according to any foregoing exampl e(s), wherein the first subset of propellers correspond to propellers of the plurality of propellers that are not positioned nearest to the at least one hull.
• Example 13 The craft according to any foregoing example(s), wherein the first subset of propellers are symmetrically positioned on the port side section and the starboard side section of the at least one wing at substantially same relative distances from the at least one hull.
• Example 14 The craft according to any foregoing example(s), wherein when the control system controls the respective rotation rate of each propeller of a first subset of propellers to be the first rotation rate that is lower than the second rotation rate at which each propeller of the second subset of propellers rotate, the control system is configured to: reduce the rotation rate of a propeller of the first subset of propellers that is on the port side section of the at least one wing and a propeller of the first subset of propellers that is symmetrically positioned on the starboard side section of the at least one wing to a same target rotation rate.
• Example 15 The craft according to any foregoing example(s), wherein after receiving the indication to reduce the airspeed of the craft, the control system is configured to: determine a target rotation rate for the plurality of propellers; reduce the rotation rate of the first subset of propellers from a first rotation rate to a second rotation rate that is lower than the target rotation rate; and reduce the rotation rate of the second subset of propellers from the first rotation rate to the target rotation rate.
• Example 16 The craft according to any foregoing example(s), wherein the indication to reduce the airspeed of the craft indicates a target airspeed of the craft, wherein after the first subset of propellers reaches the second rotation rate, the control system is configured to: while iteratively comparing an observed airspeed of the craft to the target airspeed, gradually increase the rotation rate of the first subset of propellers from the second rotation rate to the target rotation rate.
• Example 17 The craft according to any foregoing example(s), wherein the control system is configured to: determine the target rotation rate for the first subset of propellers based on a lookup table that relates different target rotation rates with different target airspeeds.
• Example 18 The craft according to any foregoing example(s), wherein the control system limits an amount by which the rotation rate of the first subset of propellers can increase or decrease to a predetermined value or lookup table based on operational parameters.
• Example 19 The craft according to any foregoing exampl e(s), wherein after receiving the indication to reduce the airspeed of the craft, the control system is configured to: determine the second rotation rate at which the first subset of propellers should rotate based at least in part on a difference between a current airspeed of the craft and the target airspeed.
• Example 20 The craft according to any foregoing example(s), wherein the control system is further configured to determine the second rotation rate at which the first subset of propellers should rotate based at least in part on an amount of time allotted to reduce the airspeed of the craft.
• control system is further configured to determine the second rotation rate at which the first subset of propellers should rotate based at least in part on an amount of drag needed to reduce the airspeed of the craft in an allotted time.
• Example 22 The craft according to any foregoing example(s), wherein the control system is configured to determine a quantity of propellers of the plurality of propellers to include in the first subset of propellers based on amount of drag needed to reduce the airspeed of the craft in the allotted time.
• control system is configured to: increase the rotation rate of the first subset of propellers relative to the second subset of propellers.
• Example 24 The craft according to any foregoing example(s), wherein after receiving the indication to reduce the airspeed of the craft, adjust a prop pitch of the first subset of propellers relative to the second subset of propellers.
• Example 25 The craft according to any foregoing example(s), wherein when operating at a particular rotation rate, an amount of roll moment induced in the craft by a wake generated by the first subset of propellers over one or more control surfaces of the craft is less than an amount of roll moment induced in the craft by a wake generated by the second subset of propellers over the one or more control surfaces of the craft.
• Example 26 The craft according to any foregoing example(s), wherein the first subset of propellers consists of a single propeller that is positioned on either the port side section or the starboard side section of the at least one wing.
• Example 27 The craft according to any foregoing example(s), wherein the single propeller is a propeller of the plurality of propellers that is positioned nearest to the at least one hull.
• Example 28 The craft according to any foregoing example(s), wherein the single propeller is a propeller of the plurality of propellers that is not positioned nearest to the at least one at least one hull.
• Example 29 The craft according to any foregoing example(s), wherein the second subset of propellers consists of a single propeller that is positioned on either the port side section or the starboard side section of the at least one wing and the single propeller is closer to the at least one hull than the propellers of the first subset of propellers.
• Example 30 The craft according to any foregoing example(s), wherein a number of propellers in the second subset of propellers is greater than a number of propellers in the first subset of propellers.
• Example 31 The craft according to any foregoing example(s), wherein the first subset of propellers includes a plurality of propeller pairs, wherein an amount by which a rate of each propeller pair is reduced is different and is based on respective distances of the propeller pairs to the at least one hull, wherein after receiving the indication to reduce an airspeed of the craft, the rotation rate of a propeller pair that is closest to the at least one hull is reduced by to a greater degree than the rotation rate of a propeller pair that is furthest from the at least one hull.
• Example 32 The craft according to any foregoing example(s), wherein the at least one wing is configured such that locations of the at least one wing over which the first subset of propellers blow air generate a least amount of lift and locations of the at least one wing over which the second subset of propellers blow air generate a most amount of lift.
• Example 33 The craft according to any foregoing example(s), wherein a given propeller from the first subset of propellers is positioned adjacent the at least one hull.
• Example 34 The craft according to any foregoing example(s), wherein a given propeller from the first subset of propellers arranged along the port side section of the at least one wing is positioned further inboard than any other propeller from the first subset of propellers arranged along the port side section of the at least one wing.
• Example 35 The craft according to any foregoing example(s), wherein a given propeller from the second subset of propellers is positioned so as to blow air over at least a portion of a control surface, and wherein a given propeller from the first subset of propellers is positioned so as to not blow air over at least the portion of the control surface.
• Example 36 The craft according to any foregoing example(s), wherein a given propeller from the second subset of propellers is positioned forward at least one portion of a respective aileron of the at least one wing, and wherein a given propeller from the first subset of propellers is not positioned forward the at least one portion of the respective aileron.
• Example 37 The craft according to any foregoing example(s), wherein the respective aileron is positioned outboard of a position of the given propeller from the first subset of propellers.
• Example 38 The craft according to any foregoing example(s), wherein a first propeller from the first subset of propellers is positioned at a first position on the port side section of the at least one wing, wherein a second propeller from the first subset of propellers is positioned at a second position on the starboard side section of the at least one wing, and wherein the first position and the second position are at substantially same relative distances from the at least one hull.
• Example 39 The craft according to any foregoing example(s), wherein a third propeller from the first subset of propellers is positioned at a third position on the port side section of the at least one wing, wherein a fourth propeller from the first subset of propellers is positioned at a fourth position on the starboard side section of the at least one wing, and wherein the third position and the fourth position are at substantially same relative distances from the at least one hull.
• controlling the respective rotation rate of each propeller of the first subset of propellers from the plurality of propellers to be the first rotation rate that is lower than the second rotation rate at which each propeller of the second subset of propellers from the plurality of propellers rotate comprises reducing (a) a rotation rate of a given propeller of the first subset of propellers that is on the port side section of the at least one wing and (b) a rotation rate of a given propeller of the first subset of propellers that is on the starboard side section of the at least one wing to a same target rotation rate.
• Example 41 The craft according to any foregoing example(s), wherein when operating at a particular rotation rate, an amount of roll moment induced in the craft by a given propeller in the first subset of propellers is less than an amount of roll moment induced in the craft by a given propeller in the second subset of propellers.
• Example 42 The craft according to any foregoing example(s), wherein the first subset of propellers consists of a first propeller that is positioned on the port side section of the at least one wing and a second propeller that is positioned on the starboard side of the at least one wing.
• Example 43 The craft according to any foregoing example(s), wherein the first propeller is positioned nearest to the at least one hull than any other propeller on the port side section of the at least one wing, and wherein the second propellers is positioned nearest to the at least one hull than any other propellers on the starboard side of the at least one wing.
• Example 44 The craft according to any foregoing example(s), wherein the first propeller is not positioned nearest to the at least one hull than any other propeller on the port side section of the at least one wing, and wherein the second propellers is not positioned nearest to the at least one hull than any other propellers on the starboard side of the at least one wing.
• Example 45 The craft according to any foregoing example(s), wherein the second subset of propellers consists of a first propeller that is positioned on the port side section of the at least one wing and a second propeller that is positioned on the starboard side of the at least one wing.
• Example 46 The craft according to any foregoing example(s), wherein the first subset of propellers includes a plurality of propeller pairs, wherein an amount by which a rate of each propeller pair is reduced is different.
• Example 47 The craft according to any foregoing example(s), wherein the at least one wing is configured such that a location of the at least one wing over which a given propeller from the first subset of propellers blows air generates a less amount of lift compared to any propeller from the second subset of propellers.
• a craft comprising: (i) at least one hull; (ii) at least one wing coupled to the at least one hull, wherein the at least one wing comprises a port side section and a starboard side section; (iii) a blown wing propulsion system that comprises a plurality of propellers arranged along the port side section and the starboard side section of the at least one wing and configured to generate lift on the craft by blowing air over the at least one wing, wherein a first subset of the propellers contributes a least amount of lift on the craft; and (iv) a control system.
• control system is configured to control a respective rotation rate of each propeller of the plurality of propellers, wherein the control system is configured to, after receiving an indication to maneuver the craft, control respective rotation rates of each propeller of the first subset of propellers to different rotation rates to induce yaw or roll into the craft.
• a craft comprising: (i) at least one hull; (ii) at least one wing coupled to the at least one hull, wherein the at least one wing comprises a port side section and a starboard side section; (iii) a blown wing propulsion system that comprises a plurality of propellers arranged along the port side section and the starboard side section of the at least one wing and configured to generate lift on the craft by blowing air over the at least one wing, wherein an amount of lift on the craft contributed by a first subset of the propellers is less than an amount of lift of on the craft contributed by a second subset of propellers when all propellers are operating at substantially the same rotation rate; and (iv) a control system.
• control system is configured to control a respective rotation rate of each propeller of the plurality of propellers, wherein the control system is configured to, after receiving an indication to maneuver the craft, change a respective rotation rate of at least one propeller from the first subset of propellers to induce at least one of yaw and roll into the craft.
• a craft comprising: (i) at least one hull, (ii) at least one wing coupled to the at least one hull, (iii )a blown wing propulsion system that comprises a plurality of propellers configured to generate lift on the craft by blowing air over the at least one wing, and (iv) a control system.
• control system is configured to: (i) determine a airspeed difference between (a) an indicated airspeed of the craft and (b) an indicated target airspeed of the craft; (ii) determine a target rotation rate based on at least the indicated target airspeed of the craft; (iii) determine a first command rotation rate for a first given propeller of the plurality of propellers based on (a) the determined airspeed difference and (b) the determined target rotation rate; and (iv) cause the first given propeller of the plurality of propellers to operate according to the determined first command rotation rate.
• Example 51 The craft according to example 50, wherein the control system is further configured to cause a second given propeller of the plurality of propellers to operate according to the determined target rotation rate while the first given propeller of the plurality of propellers operates according to the determined first command rotation rate.
• Example 52 The craft according to any foregoing example(s), wherein determining the first command rotation rate for the first given propeller of the plurality of propellers is further based on a predetermined rotation delta limit.
• a craft comprising: (i) at least one hull, (ii) at least one wing coupled to the at least one hull, (iii) a blown wing propulsion system that comprises a plurality of propellers configured to generate lift on the craft by blowing air over the at least one wing, and (iv) a control system.
• control system is configured to: (i) while each propeller in the plurality of propellers is operating at a first rotation rate, receive an indication to adjust an airspeed of the craft, and (ii) after receiving the indication to adjust the airspeed of the craft, adjust a rotation rate of a first subset of propellers of the plurality of the propellers such that the first subset of propellers each begin to operate at a second rotation rate while each of the propellers of a second subset of propellers of the plurality of propellers continues to operate at the first rotation rate.
• control system further configured to, after adjusting the rotation rate of the first subset of propellers of the plurality of the propellers such that the first subset of propellers each begin to operate at a second rotation rate, adjust a rotation rate of the second subset of propellers of the plurality of the propellers such that the second subset of propellers each begin to operate at a third rotation rate while each of the propellers of the first subset of propellers of the plurality of propellers continues to operate at the second rotation rate.
• control system further configured to, after adjusting the rotation rate of the first subset of propellers of the plurality of the propellers such that the first subset of propellers each begin to operate at a second rotation rate, adjust the rotation rate of the first subset of propellers of the plurality of the propellers such that the first subset of propellers each begin to operate at the first rotation rate.
• a craft comprising: (i) at least one hull, (ii) at least one wing coupled to the at least one hull, (iii) a blown wing propulsion system that comprises a plurality of propellers configured to generate lift on the craft by blowing air over the at least one wing, and (iv) a control system.
• control system is configured to, (i) while each propeller in the plurality of propellers is operating at a first rotation rate, receive an indication to adjust an airspeed of the craft, and (ii) after receiving the indication to adjust the airspeed of the craft: (a) adjust a rotation rate of a first subset of propellers of the plurality of the propellers such that the first subset of propellers each begin to operate at a second rotation rate after a first amount of time, (b) adjust a rotation rate of the second subset of propellers of the plurality of the propellers such that the second subset of propellers each begin to operate at a third rotation rate after a second amount of time, wherein the second amount of time is longer than the first amount of time, and (c) while the second subset of propellers are each operating at the third rotation rate, adjust the rotation rate of the first subset of propellers of the plurality of propellers such that the first subset of propellers begin to operate at a rotation rate that is the
• Example 57 The craft according to example 56, wherein the indication to adjust the airspeed is an indication to decrease the airspeed.
• Example 60 The craft according to any foregoing example(s), wherein the rotation rate that is the same as the rotation rate at which the second subset of propellers of the plurality of the propellers are operating is a fourth rotation rate.
• control system further configured to determine the second rotation rate based on at least the received indication to adjust the airspeed of the craft.
• determining the second rotation rate based on at least the received indication to adjust the airspeed of the craft comprises determining the second rotation rate based on at least the received indication to adjust the airspeed of the craft and a received indication of a current airspeed of the craft.
• Example 65 The craft according to any foregoing example(s), wherein while each propeller in the plurality of propellers is operating at the first rotation rate a given propeller in the first subset of propellers is operating at a first pitch, and wherein the control system further configured to after receiving the indication to adjust the airspeed of the craft, adjust the pitch of the first subset of propellers of the plurality of the propellers such that the given propellers in the first subset of propellers begins to operate at a second pitch while the given propeller in the first subset of propellers operates at the second rotation rate.
• control system further configured to, after receiving the indication to adjust the airspeed of the craft, determining which of the plurality of propellers to include in the first subset of propellers based on one or more of (a) the received indication to adjust the airspeed of the craft, (b) a received indication of a current airspeed of the craft, (c) a time allotted to change the airspeed, and (d) an environmental condition.
• Example 68 The craft according to any foregoing example(s), wherein the plurality of propellers comprises twelve propellers, and wherein the first subset of propellers comprises four propellers.
• Example 69 The craft according to any foregoing example(s), wherein the plurality of propellers comprises twelve propellers, and wherein the first subset of propellers comprises six propellers.
• Example 70 The craft according to any foregoing example(s), wherein the plurality of propellers comprises eight propellers, and wherein the first subset of propellers comprises two propellers.
• Example 71 The craft according to any foregoing example(s), wherein the plurality of propellers comprises eight propellers, and wherein the first subset of propellers comprises four propellers.
• Example 72 The craft according to any foregoing example(s), wherein each propeller in the first subset of propellers of the plurality of the propellers is positioned closer to the at least one hull than any propeller in the second subset of propellers of the plurality of propellers.
• Example 73 The craft according to any foregoing example(s), wherein the indication to adjust the airspeed of the craft comprises an indication to begin a landing procedure.

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• 2024
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