Rotorcraft including a fuselage and at least three rotor system arms each having a rotor system. Each rotor system includes a mast having at least two rotor blades and an electric rotor motor. At least one rotor system arm includes a support mechanism for pivotally supporting a floating mast about at least one pivot axis whereby the floating mast is tillable relative to a fiducial tilt position. The floating mast has a controllable cyclic rotor blade pitch. A mast tilt measurement mechanism provides a mast tilt feedback signal regarding a measured tilt position of a floating mast relative to its fiducial tilt position. A flight control system continuously controls the at least three electric rotor motors and the floating masts cyclic rotor blade pitch in response to a desired input maneuver and its mast tilt feedback signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Section 371 of International Application No PCT/IL2021/051418, filed Nov. 29, 2021, which was published in the English language on Jun. 2, 2022, under International Publication No. WO 2022/113087 A1, which claims priority under 35 U.S.C. § 119 (b) to Israeli Application No. 279111, filed Nov. 30, 2020, Israeli Application No. 280231, filed Jan. 17, 2021, and Israeli Application No. 282499, filed Apr. 20, 2021, the disclosures of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to rotorcraft.

BACKGROUND OF THE INVENTION

Rotorcraft extend the gamut from helicopters with a single rotor system to multirotor rotorcraft having two or more rotor systems. Rotorcraft include Vertical Take-Off and Landing (VTOL) rotorcraft and Short Take-Off and Landing (STOL) rotorcraft. Input of a desired maneuver of a rotorcraft, for example, takeoff, hovering, flying to a destination, landing, and the like, can be by way of a Remote Control (RC) unit, controls operated by an onboard pilot, an autopilot, and possibly a combination of two or more thereof.

Traditional rotorcraft maneuvering requires control of a lift force component acting vertically upward to overcome weight and a thrust force component for steering purposes. Accordingly, a resultant lift-thrust force leads to tilting of a rotorcraft in a direction of flight which militates against technical performance by inter alia increasing drag, decreasing responsiveness, and the like.

There is a need for rotorcraft having improved technical and maneuvering capabilities.

SUMMARY OF THE INVENTION

The present invention is directed towards rotorcraft, components therefor, methods of operation therefor, and systems and methods for landing rotorcraft. Rotorcraft of the present invention include a fuselage having at least three preferably rigid rotor system arms mounted on the fuselage each having a rotor system, and a flight control system for controlling the rotor systems in accordance with a desired input maneuver, for example, takeoff, hovering, flying to a destination, landing, and the like. Each rotor system includes a mast having at least two rotor blades and an electric rotor motor coupled to the mast for driving the mast whereupon the at least two rotor blades act as a rotating rotor disc. One or more rotor system arms each include a support mechanism for pivotally supporting a floating mast about a single pivot axis or dual pivot axes. Dual pivot axes are preferably orthogonal. A floating mast has controllable cyclic rotor blade pitch. A floating mast optionally has controllable collective rotor blade pitch. A mast tilt measurement mechanism measures tilt of a floating mast relative to a fiducial tilt position and provides a mast tilt feedback signal regarding same.

The flight control system continuously controls the rotor systems and a floating mast's cyclic rotor blade pitch in response to the desired input maneuver and the mast tilt feedback signal wherein the continuous control of the floating mast's cyclic rotor blade pitch includes the following three steps: First, at an initial tilt position of the floating mast, actuating minor cyclic rotor blade pitch adjustments to maintain the floating mast at its initial tilt position. Second, actuating a major cyclic rotor blade pitch adjustment for tilting the floating mast from its initial tilt position to a desired tilt position. In other words, a change in a floating mast's tilt position is enabled by lift forces by virtue of a change in its cyclic rotor blade pitch as opposed to the conventional use of a servo-driven actuator. And third, upon arrival at its desired tilt position, neutralizing the major cyclic rotor blade pitch adjustment and reverting to actuating minor cyclic rotor blade pitch adjustments to maintain the floating mast at its desired tilt position. The minor cyclic rotor blade pitch adjustments at the floating mast's initial tilt position and subsequently at its desired tilt position are in order to overcome instantaneous changes e.g. changes caused by wind forces, and the like. Tilting of a floating mast by way of cyclic rotor blade pitch typically occurs over short periods of several milliseconds. Tilting of a floating mast applies a resultant force to its rotor system arm in the general direction of its tilt which in turn applies a resultant force to a rotorcraft as a whole. The resultant force on a rotorcraft as a whole depends on deployment of a rotor system arm relative to a rotorcraft's center of gravity.

Support mechanisms for pivotally supporting a floating mast about a single pivot axis can be implemented by a single bearing, a pair of opposite and parallel bearings, being slidingly supported on a single rail or a pair of opposite and parallel rails, and the like. Single axis support mechanisms pivotally support a floating mast along a single straight tilt line in a top plan view of a rotor system arm at an included angle α where 0°≤α≤180° with its longitudinal rotor system arm centerline. Accordingly, a single straight tilt line of a floating mast pivotally mounted on a single axis support mechanism can be fixedly set between being co-directional with a longitudinal rotor system arm centerline and perpendicular thereto. A floating mast pivotally mounted on a single axis support mechanism can be driven by an electric rotor motor either directly mounted thereon or via a conventional linkage mechanism. The support mechanisms can include damping mechanisms and/or shock absorbing mechanisms for their improved mechanical operation.

Support mechanisms for pivotally supporting a floating mast about dual pivot axes can be implemented by bearings, rails, and the like. Dual axis support mechanisms enable a floating mast to pivot along two-predetermined straight tilt lines which can each subtend an included angle β where 0°≤β≤180° relative to a longitudinal rotor system arm centerline. The two tilt lines are preferably orthogonal.

Cyclic rotor blade pitch of a floating mast's rotor blades can be implemented by either a traditional swashplate mechanism including one or more servos or alternatively as described in U.S. Pat. No. 9,914,535 to Paulos entitled Passive Rotor Control Mechanism for Micro Air Vehicles, incorporated herein by reference.

Mast tilt measurement mechanisms employ conventional tilt measuring technologies for measuring a mast tilt relative to a fiducial tilt position and providing a mast tilt feedback signal regarding same. Tilt measurements can be gravitational measurements or relative to a rotor system arm. Conventional tilt measuring technologies include inter alia gravitational accelerometers, encoder arrangements, optical arrangements, laser arrangements, and the like.

Rotorcraft of the present invention are effectively afforded one or more additional degrees of freedom for maneuvering purposes compared to traditional rotorcraft by virtue of each floating mast being individually and independently tiltable. The present invention can be implemented on either an odd number of rotor systems or an even number of rotor systems from model rotorcraft to full sized passenger and/or payload carrying rotorcraft. The present invention can also be implemented on a co-axial rotor system including either an electric rotor motor for rotating a lower mast having at least two rotor blades and an electric rotor motor for rotating an upper mast having at least two rotor blades or one an electric rotor motor that rotates both co-axial rotor systems. The number of floating masts ranges from a single floating mast to each mast being floatable. More floating masts improves a rotorcraft's technical capabilities. Some rotorcraft can preferably include single axis support mechanisms only. Other rotorcraft can preferably include dual axis support mechanisms only. Still other rotorcraft can preferably include a combination of at least one single axis support mechanism and at least one dual axis support mechanism. Implementations of support mechanisms cyclic rotor blade pitch and mast tilt measurements are dependent on a rotorcraft's intended purpose.

Rotorcraft including one or more floating masts in accordance with the present invention have considerably improved maneuverability compared to their traditional counterparts by virtue of their maneuverability being achieved by adjusting tilt of one or more floating masts as opposed to tilting an entire rotorcraft. For example, when flying to a destination, a rotorcraft can tilt its one or more floating masts forward thereby keeping its fuselage at its best aerodynamic orientation by controlling rpm and/or collective rotor blade pitch. In another example, transitioning between hovering and flight has a much faster response time and a considerable energy saving compared to a conventional comparable rotorcraft. And in a yet further example, yaw transitions are quicker compared to a conventional comparable rotorcraft.

Rotorcraft of the present invention can preferably also include a forward propulsion unit for assisting forward flight. The forward propulsion unit can be implemented as an electrical unit or a combustion unit depending on technical parameters including inter alia size, weight, maximum payload, maximum range, maximum flight time, and the like. The forward propulsion unit can be implemented by a rear mounted pusher, two or more side mounted pushers, a front mounted puller or a combination thereof. The forward propulsion unit facilitates emergency autorotation for safe emergency landings in the event of a catastrophic loss of one or more rotor systems. The forward propulsion unit also facilitates gyro-cruising similar to an auto-gyro. Such emergency autorotation and auto-cruising can be further assisted by providing the rotor systems with freewheel arrangements such that a mast can freewheel autorotate without being driven by its electric rotor motor. Freewheel arrangements can be implemented by mechanical freewheel mechanisms. Alternatively, in the case of electrical rotor system motors, a freewheel arrangement can be implemented by a non-mechanical arrangement.

Rotorcraft of the present invention preferably include aerodynamic lifting surfaces. Rotor system arms can be configured as aerodynamic wings for providing lift. Alternatively, a rotorcraft's fuselage can be provisioned with aerodynamic wings for providing lift.

Rotorcraft of the present invention can include a commercially available Airborne Collision Avoidance System (ACAS) for assisting both indoor and outdoor flight applications.

Rotorcraft of the present invention synergistically combine three traditionally separate aerodynamic concepts of helicopter, autogyros and fixed wing aircraft for providing VTOL/STOL, hovering, autogyro flight efficiency and fixed wing range, speed and payload capacity. The flight envelope of the rotorcraft of the present invention has positively overlapping flight phases as follows: taking off like a VTOL/STOL rotorcraft, accelerating and ascending like an autogyro, high-speed gyro-cruising for straight and level flight like an autogyro and/or fixed wing aircraft, decelerating and descending like an autogyro, and landing like a VTOL/STOL rotorcraft. Exemplary rotorcraft speed ranges for takeoff/landing are between about 0 knots and about 30 knots, accelerating and ascending/decelerating and descending between about 15 knots and about 80 knots, and high-speed gyro-cruising from about 60 knots to about 100 knots. The positive overlapping flight phases means transitioning between flight phases doesn't pose a risk to the rotorcraft regardless of speed and altitude potential, eliminating a helicopter's deadman's curve and guaranteeing safe flight operation at all flight phases even in the event of power loss.

DETAILED DESCRIPTION OF PRESENT INVENTION

The detailed description of the drawings is divided into the following six sections:Section 1: Rotorcraft with Floating MastSection 2: Single Axis and Dual Axis Support Mechanisms for Pivotally Supporting Floating MastsSection 3: Cyclic Rotor Blade Pitch ControlsSection 4: Rotorcraft with Forward Propulsion UnitSection 5: Rotorcraft Steering and Rotorcraft ManeuversSection 6: Technical Benefits of Rotorcraft with Forward Propulsion Unit and one or more Floating Masts

Section 1: Rotorcraft with Floating Mast

For illustrative purposes only, the present invention is now described with respect to a tricopter having a single floating mast.

FIG.1AandFIG.1Bshow a tricopter10including a fuselage11at an intersection of three preferably rigid rotor system arms12A,12B and12C. The fuselage11can be designed for passengers and/or payload and can have different shapes and sizes. The rotor system arms12A,12B and12C correspondingly include rotor systems13A,13B and13C displaced from the fuselage11. In small scale rotorcraft, control of the rotor systems13A,13B and13C for adjusting rotorcraft inclination is typically by rpm only. In large scale rotorcraft, control of the rotor systems13A,13B and13C for adjusting rotorcraft inclination is by rpm and/or collective rotor blade pitch.

The rotor systems13A and13B correspondingly have a fixedly mounted mast14A and a fixedly mounted14B mast each having an opposite pair of fixed pitch rotor blades16A and16B. The rotor systems13A and13B correspondingly have electric rotor motors17A and17B coupled to their masts14A and14B for driving same such that opposite pairs of fixed pitch rotor blades16A and16B act as rotor discs18A and18B graphically represented as circles. The rotor systems13A and13B are counter rotating thereby compensating each other torque at the same rpm, thereby having zero resultant torque.

The rotor system arm12C has a longitudinal rotor system arm centerline19and includes either a single axis or a dual axis support mechanism21for pivotally supporting a floating mast22having an opposite pair of rotor blades23. The rotor system13C includes an electric rotor motor24coupled to the floating mast22for driving same such that the opposite pair of rotor blades23act as a rotor disc26graphically represented as a circle. The electric rotor motor24can be directly coupled to the floating mast22whereby the electric rotor motor24tilts simultaneously with the floating mast22. Alternatively, the electric rotor motor24can be stationary and coupled to the floating mast22by a linkage mechanism, thereby reducing the weight of the floating mast22. The floating mast22has a tilt angle ⊖ with respect to vertical where ⊖≤±80° as shown inFIG.6. The single axis support mechanism21A and the dual axis support mechanism21B can provide mechanical stops for the floating mast22.

The tricopter10is enabled with conventional collective control27of the collective rotor blade pitch of the three rotor systems13A-13C and conventional cyclic control28of the cyclic rotor blade pitch of the rotor system13C only. The rotor systems13A-13C have individually controllable collective rotor blade pitch. The rotor system13C preferably includes a servo-controlled swashplate mechanism for enabling individual or simultaneous adjustment of its collective rotor blade pitch and cyclic rotor blade pitch. The rotor system13C can include alternative mechanisms for enabling individual or simultaneous adjustment of its collective rotor blade pitch and cyclic rotor blade pitch.

The tricopter10includes a mast tilt measurement mechanism29for measuring a tilt of the floating mast22relative to a fiducial tilt position. Suitable commercially available gravitational accelerometers for measuring a floating mast's tilt include inter alia a FXOS8700CQ accelerometer commercially available from NXP Semiconductors N.V.

The tricopter10includes a Flight Control System (FCS)31for receiving a multitude of input signals regarding attitude of the tricopter, flight conditions, and the like. The FCS31also receives a desired input maneuver for the tricopter10and a mast tilt feedback signal from the mast tilt measurement mechanism29regarding the floating mast22's tilt position relative to its fiducial tilt position. The FCS31outputs control signals for continuously controlling the rotor systems13A-13C for executing the desired input maneuver and compensate for instantaneous changes.

The FCS31is a computing device including at least one processing unit and optionally a memory. The presently disclosed subject matter, or certain aspects or portions thereof, may take the form of program code embodied in computer readable storage medium for loading into a computing device whereupon the computing device becomes the FCS31.

The FCS31continuously controls the floating mast22in response to the mast tilt feedback signal for executing the following steps: At an initial tilt position of the floating mast22, the FCS31actuates minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat. Second, the FCS31actuates a major cyclic rotor blade pitch adjustment for tilting the floating mast22from its initial tilt position to a desired tilt position. And thirdly, upon arrival at the desired tilt position, the FCS31neutralizes the major cyclic rotor blade pitch adjustment and reverts to actuating minor cyclic rotor blade pitch adjustments to maintain the floating mast22at its desired tilt position. A major cyclic rotor blade pitch adjustment to achieve a desired tilt position is typically in the order of milliseconds. The tilt angle between an initial tilt position and a desired tilt position is typically in the order of about 45°.

The tricopter10can include an Advanced Collision Avoidance System (ACAS)32for assisting indoor and outdoor flight applications. The ACAS32includes inter alia sonar sensors, IR sensors, LIDAR sensors, and the like. The ACAS32is also employable for avoiding ground collisions. The ACAS32is commercially available from FlytBase, Inc, www.flytbase.com and similar vendors.

FIG.2Ashows the tricopter10with a pair of aerodynamic wings33.

FIG.2BandFIG.2Cshow the tricopter10with rotor system arms12configured as aerodynamic wings for providing lift.

FIG.3shows a single axis support mechanism21A pivotally supporting the floating mast22along a single pre-determined straight tilt line which subtends an included fixed angle α where 0°≤α≤180° relative to the longitudinal rotor system arm centerline19in a top plan view of the rotary system arm12C. The single axis support mechanism21A is preferably designed to pivotally support a floating mast22either co-directional with the rotor system arm12C in the top plan view or perpendicular to the rotor system arm12C in the top plan view.

FIG.4shows a dual axis support mechanism21B pivotally supporting the floating mast22along two pre-determined straight tilt lines which can each subtend an included angle β where 0°≤β≤180° relative to the longitudinal rotor system arm centerline19in a top plan view of the rotary system arm12C. The two tilt lines are preferably orthogonal for facilitating control of a floating mast22.FIG.4shows two exemplary straight tilt lines β1=45° and β2=135° relative to the longitudinal rotor system arm centerline19.

FIG.5toFIG.10show a single axis support mechanism21A pivotally supporting the floating mast22about a pivot axis34co-axial with the longitudinal rotor system arm centerline19.FIG.5,FIG.7andFIG.9show lift-thrust forces on four quadrants of the rotor disc26in the top plan view.FIG.6,FIG.8andFIG.10show lift-thrust forces on the two quadrants of the rotor disc26on opposite sides of the floating mast22in the right side elevation view.FIG.10shows the rotor disc26applies a resultant force RF on the rotor system arm12C in the floating mast22's general direction. The resultant force RF has a vertical lift component and a horizontal thrust component for steering and/or maneuvering purposes.

FIG.5andFIG.6show the floating mast22in an initial tilt position. Cyclic rotor blade control is continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.FIG.7andFIG.8show a transitory major cyclic rotor blade pitch adjustment to tilt the floating mast22from the initial tilt position to a desired tilt position. Such transitory major cyclic rotor blade pitch adjustments typically last a short duration of few milliseconds. The desired tilt position is typically within ±30° with respect to the vertical.FIG.9andFIG.10show neutralization of the major cyclic rotor blade pitch adjustment at the floating mast22's desired tilt position. Cyclic rotor blade control is again continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.

FIG.11toFIG.16show a single axis support mechanism21A pivotally supporting the floating mast22about a pivot axis36perpendicular to the longitudinal rotor system arm centerline19in a front elevation view thereof.FIG.11,FIG.13andFIG.15show lift-thrust forces on four quadrants of the rotor disc26.FIG.12,FIG.14andFIG.16show lift-thrust forces on the two quadrants of the rotor disc26on opposite sides of the floating mast22in the front elevation view.FIG.16shows the rotor disc26applies a resultant force RF on the rotor system arm12C in the floating mast22's general direction. The resultant force RF has a vertical lift component and a horizontal thrust component for steering and/or maneuvering purposes.

FIG.11andFIG.12show the floating mast22in an initial tilt position. Cyclic rotor blade control is continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.FIG.13andFIG.14show a transitory major cyclic rotor blade pitch adjustment to tilt the floating mast22from the initial tilt position to a desired tilt position. Such transitory major cyclic rotor blade pitch adjustments typically last a short duration of few milliseconds. The desired tilt position is typically within ±30° with respect to the vertical.FIG.15andFIG.16show neutralization of the major cyclic rotor blade pitch adjustment at the floating mast22's desired tilt position. Cyclic rotor blade control is again continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.

FIG.17toFIG.22show a dual axis support mechanism21B pivotally supporting the floating mast22about orthogonal pivot axes37and38correspondingly co-axial with the longitudinal rotor system arm centerline19and perpendicular thereto such that the floating mast22tilts at both about the rotor system arm12C in a right side elevation view thereof and co-directional with the rotor system arm12C in a front elevation view thereof.FIG.17,FIG.19andFIG.21show the lift-thrust forces on four quadrants of the rotor disc26.FIG.19shows an arrow depicting the combined movement of the floating mast22.FIG.18A,FIG.20AandFIG.22Ashow lift-thrust forces on the two quadrants of the rotor disc26on opposite sides of the floating mast22in the right side elevation view.FIG.18B,FIG.20BandFIG.22Bshow lift-thrust forces on the two quadrants of the rotor disc26on opposite sides of the floating mast22in the front elevation view.FIG.22AandFIG.22Bshow the rotor disc26applies a resultant force RF on the rotor system arm12C in the floating mast22's general direction. The resultant force RF has a vertical lift component and a horizontal thrust component for steering and/or maneuvering purposes.

FIG.17,FIG.18AandFIG.18Bshow the floating mast22in an initial tilt position. Cyclic rotor blade control is continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.FIG.19,FIG.20AandFIG.20Bshow a transitory major cyclic rotor blade pitch adjustment to tilt the floating mast22from the initial tilt position to a desired tilt position. Such transitory major cyclic rotor blade pitch adjustments typically last a short duration of few milliseconds. The desired tilt position is typically within ±30° with respect to the vertical.FIG.21,FIG.22AandFIG.22Bshow neutralization of the major cyclic rotor blade pitch adjustment at the floating mast22's desired tilt position. Cyclic rotor blade control is again continuously employed for causing minor cyclic rotor blade pitch adjustments to maintain the floating mast22thereat to compensate for instantaneous changes.

Section 2: Single Axis and Dual Axis Support Mechanisms for Pivotally Supporting Floating Masts

Single axis support mechanisms for pivotally supporting a floating mast can be implemented by single bearings, pairs of opposite and parallel bearings, single rails, pairs of opposite and parallel rails, and the like. Dual axis support mechanisms for pivotally supporting a floating mast can be implemented by bearings, rails, and the like. Selection of an implementation of a support mechanism depends on a number of factors including inter alia size and weight of a rotorcraft, desired maximum degree of tilting, pivot axis and the like.

FIG.23andFIG.24show a rotor system arm40with a longitudinal rotor system arm centerline41and having a single axis support mechanism42with a pair of opposite and parallel bearings43on either side of the longitudinal rotor system arm centerline41for providing a pivot axis44perpendicular thereto and intercepting same. The pivot axis44is necessarily beneath a juncture between the floating mast22and opposite pair of rotor blades23.

FIG.25andFIG.26show the rotor system arm40having a single axis support mechanism46with a pair of opposite and parallel curved rails47deployed on both sides of the longitudinal rotor system arm centerline41. The pair of opposite and parallel curved rails47are preferably deployed symmetrical with respect to the vertical. The single axis support mechanism46can be readily designed to provide a pivot axis48adjacent the juncture between the floating mast22and the opposite pair of rotor blades23, thereby affording a more stable arrangement than the single axis support mechanism42. The single axis support mechanism46can be readily designed to control the location of the pivot axis48relative to the rotor system arm40.FIG.25andFIG.26show the single axis support mechanism46has a pair of opposite and parallel curved rails47with a radius of curvature R1such that the pivot axis48is at the juncture between the floating mast22and the opposite pair of rotor blades23.FIG.27shows the single axis support mechanism46has a pair of opposite and parallel curved rails47with a radius of curvature R2greater than the radius of curvature R1thereby elevating the pivot axis48above the juncture between the floating mast22and the opposite pair of rotor blades23.

The single axis support mechanisms42and46can equally be used for providing a pivot axis codirectional with the rotor system arm40whereby a floating mast22tilts about the rotor system arm40in a right side elevation view.

FIG.28show the rotor system arm40with a dual axis support mechanism49having a first pair of opposite and parallel bearings51and an orthogonal pair of opposite and parallel bearings52for pivotally supporting a floating mast53having a hinged rotor as described in aforementioned U.S. Pat. No. 9,914,535 to Paulos,

FIG.29andFIG.30show the rotor system arm40with a dual axis support mechanism54having a bearing56along with the longitudinal rotor system arm centerline41for pivotally supporting a mast support57thereabout in a right side elevation view. The mast support57includes the pair of opposite and parallel bearings43.

FIG.31andFIG.32show the rotor system arm40with a dual axis support mechanism58having the pair of opposite and parallel curved rails47supporting a mast support57which in turn has a pair of opposite and parallel curved rails59perpendicular to the longitudinal rotor system arm centerline41.

Section 3: Cyclic Rotor Blade Pitch Controls

FIG.33AtoFIG.33CandFIG.34show different cyclic rotor blade pitch controls for tilting a floating mast.FIG.33Ashows a single servo swashplate mechanism60for deployment with a single axis support mechanism.FIG.33Bshows a dual servo swashplate mechanism61for deployment with a dual axis support mechanism. Alternatively, the dual servo swashplate mechanism61can be employed for deployment with a single axis support mechanism and providing collective rotor blade pitch control of a floating mast.FIG.33Cshows a triple servo swashplate mechanism62for deployment with a dual axis support mechanism and also providing collective rotor blade pitch control of a floating mast.FIG.34shows a hinged rotor63as described in aforementioned U.S. Pat. No. 9,914,535 to Paulos as an alternative to servo swashplate mechanism for tilting a floating mast mounted on either a single axis support mechanism or a dual axis support mechanism.

Section 4: Rotorcraft with Forward Propulsion Unit

FIG.35AandFIG.35Bshow the tricopter10additionally including a forward propulsion unit64configured as a rear mounted pusher. Alternatively, the forward propulsion unit64can be implemented by two or more side mounted pushers, a front mounted puller or a combination thereof. The flight control system31also controls the forward propulsion unit64along with the rotor systems13A-13C.FIG.36Ashows a vectored thrust rear mounted pusher66for improving handling qualities.FIG.36BandFIG.36Cshow vectored thrust rear mounted pusher66providing thrust in two exemplary directions:FIG.36Bshows right thrust generating counterclockwise torque andFIG.36Cshows down thrust resulting in pitching up torque.

The tricopter10has a pre-determined total take-off payload weight and an optimal flight speed for cruising flight at a non-descending altitude. The tricopter10at a predetermined total take-off payload weight has an overall drag at its optimal speed. The rotorcraft10with the forward propulsion unit64's assistance is capable of straight and level gyro-cruising flight when the electric rotor motors17A-17C of the rotor systems13A-13C are powered up to 25% of their maximum power. The tricopter10can be provided with a more powerful forward propulsion unit64such that the tricopter is capable of straight and level gyro-cruising flight when the electric rotor motors17A-17C of the rotor systems13A-13C are not powered. The floating mast functionality allows gyro-cruising flight at a low platform angle of attack relative to air flow resulting in improved energy consumption.

Section 5: Rotorcraft Steering and Rotorcraft Maneuvers

Exemplary rotorcraft steering and rotorcraft maneuvers achievable by a rotorcraft with one or more floating masts are now described. For explanatory purposes, a Cartesian coordinate system is employed wherein forward flight is along the X axis and sideways flight is along the Y axis. Forward flight and/or sideways flight can be achieved without an entire rotorcraft having to be tilted as presently required with conventional rotorcraft, thereby affording considerably reduced drag. Furthermore, in the case of a rotorcraft having one or more lifting surfaces, greater lift efficiency can be achieved by controlling its fuselage's angle of attack which correspondingly changes the lifting surfaces' angle of attack. Moreover, responsiveness of a rotorcraft with one or more floating masts to a desired input maneuver is considerably quicker than responsiveness of a rotorcraft requiring its entire tilting for the same desired input maneuver. In the case of a rotorcraft having rotor systems without collective rotor blade pitch control, rpm control is employed for controlling a rotorcraft's inclination. In the case of a rotorcraft having rotor systems with collective rotor blade pitch control, a rotorcraft's inclination can be controlled by rpm and/or collective rotor blade pitch.

Traditional rotorcraft with three or more rotor systems has pairs of counter-rotating rotor systems. Accordingly, a traditional rotorcraft with an odd number of rotor systems has a resulting residual clockwise or counterclockwise torque.

FIG.37andFIG.38show the tricopter10with a single axis support mechanism21A for tilting the floating mast22to a desired tilt position for affording yaw shown an exemplary clockwise yaw. The rotor disc26has a higher rpm and/or higher collective rotor blade pitch than the rotor disc18A and the rotor disc18B to compensate for the floating mast22's tilting and preclude tilting the fuselage11. The yaw can also be provided by a dual axis support mechanism supporting the floating mast22. The yaw can be more easily afforded by multiple floating masts.

FIG.39andFIG.40show the tricopter10with a dual axis support mechanism21B for affording both yaw and pitch. The rotor disc26has a higher rpm and/or higher collective rotor blade pitch than the rotor disc18A and the rotor disc18B to compensate for the floating mast22's tilting and preclude tilting the fuselage11as occurs in a traditional tricopter as shown inFIG.41.

FIG.42toFIG.47show a quadcopter70with an increasing number of floating masts for progressively improving its steering. For illustrative purposes, the quadcopter70is provided with one or more single axis support mechanisms21A. Two single axis support mechanisms21A for pivotally supporting two floating masts in two different directions can be replaced by a dual axis support mechanism21B.

FIG.42andFIG.43show a quadcopter70with four rotor system arms71A-71D having a first pair of diagonally opposite counter-rotating rotor systems72A and72B and a second pair of diagonally opposite counter-rotating rotor systems72C and72D thereby resulting in a resultant zero torque. The rotor system arm71A has a single axis support mechanism21A for tilting a floating mast73A therealong for facilitating25forward flight. The rotor system72A has a higher rpm and/or higher collective rotor blade pitch than the rotor systems72B-72D to compensate for the floating mast73A′s tilting and preclude tilting the quadcopter70.

FIG.44andFIG.45show the rotor system arm71B has a single axis support mechanism21A for tilting a floating mast73B thereabout for affording yaw shown as exemplary clockwise yaw. The rotor system72B has a higher rpm and/or higher collective rotor blade pitch than the rotor systems72A,72C and72D to compensate for the floating mast73B's tilting and preclude tilting the quadcopter70.

FIG.46andFIG.47show the rotor system arm71C has a single axis support mechanism21A for tilting a floating mast73C there along for enabling sideways flight. The rotor system72C has a higher rpm and/or higher collective rotor blade pitch than the rotor systems72A,72B and72D to compensate for the floating mast73C's tilting and preclude tilting the quadcopter70.

FIG.48toFIG.53show a quadcopter80with a fuselage81and four rotor system arms82A-82D each having a dual axis support mechanism21B for correspondingly pivotally supporting rotor systems83A-83D. The quadcopter has four floating masts84A-84D and rotating rotor discs86A-86D including a pair of counterrotating rotor discs86A and86B and a pair of counterrotating rotor discs86C and86D. The quadcopter80includes a rear mounted pusher87similar to the rear mounted pusher64.

FIG.49shows the quadcopter80in forward flight. The quadcopter's four floating masts84A-84D are tilted forward with respect to the vertical for providing lift and forward thrust, thereby enabling the fuselage81to assume an aerodynamic efficient position, in this case, horizontal, for reducing drag. The forward propulsion unit87can optionally be operated.

FIG.50shows the quadcopter80in sideways flight. The quadcopter's four floating masts84A-84D are tilted sideways with respect to the vertical for providing lift and sideways thrust, thereby enabling the fuselage81to assume an aerodynamic efficient position, in this case, horizontal, for reducing drag. The forward propulsion unit87can optionally be operated.

FIG.51shows use of the four floating masts84A-84D to turn the quadcopter80clockwise. The forward propulsion unit87can optionally be operated.

FIG.52shows the quadcopter80in forward flight under gyro-cruising on operation of the forward propulsion unit87. The floating masts84A-84D are necessarily tilted backwards with respect to the quadcopter's forward flight such that their rotating rotor discs86A-86D present a positive angle of attack for enabling their autorotation as opposed to being motor driven. The floating masts84A-84D are preferably tilted for positioning the fuselage81in an aerodynamic efficient position, in this case, horizontal, for reducing drag.

FIG.53shows the quadcopter80is capable for flying in the case of a catastrophic malfunction of a rotor system, in this case, the rotor system83A. Loss of the rotor system83A can be compensated by means of suitable cyclic control of the remaining rotor systems83B,83C and83D.

Rotorcraft of the present invention also afford substantially vertical landing on inclined landing areas including inter alia open terrain, roofs, stationary or moving transportation means, and the like. Such vertical landing can be operator controlled, semi-automatic or fully automatic. Transportation means can be land-based or sea-based. Land-based transportation means can be stationary or moving. Sea-based transportation means are nearly continuously moving by virtue of wave action. Rotorcraft of the present invention necessarily require inclination details of a landing area for safe vertical descent thereon. In the case of open terrain, commercially available topographic maps include inter alia inclination details. Accordingly, a rotorcraft's flight plan can include landing at a destination with known topographic details. Otherwise inclination details of a landing area can be obtained by either on-board rotorcraft means or telemetry apparatus provided on a landing area for measuring and transmitting same to a rotorcraft intending to land thereon. The on-board rotorcraft means can be provided as part of a commercially available Airborne Collision Avoidance System (ACAS).

Landing on an inclined landing area involves changing a fuselage's inclination from being typically horizontal as its hovers above a desired landing area to substantially match the landing area's inclination. A fuselage's inclination can be changed either by way of rpm control and/or collective pitch. In the case of a conventional rotorcraft with fixed masts, such change would lead to a lateral displacement of the rotorcraft from its hovering position above a desired landing area. Rotorcraft of the present invention preclude such lateral displacement by simultaneous tilting of its one or more floating masts. Rotorcraft of the present invention preferably have each rotor system arm having a floating mast pivotally supported by a single axis support mechanism or preferably a dual axis support mechanism for landing on a stationary landing area. Landing on a landing area with a continuously changing inclination preferably requires that each floating mast is pivotally supported by a dual axis support mechanism.

FIG.54toFIG.56show landing the quadcopter80on an inclined landing area in open terrain. The quadcopter80includes sensors for measuring distances to objects, for example, for collision avoidance. The quadcopter80can employ the same sensors for measuring distances to the landing area.FIG.54shows the quadcopter80hovering above the inclined landing area. The quadcopter's fuselage81is generally horizontal.FIG.55shows inclining the fuselage81compared to itsFIG.54inclination to correspondingly match the inclined landing area. The fuselage81's change of inclination is achieved by the front rotor systems have a higher rpm and/or collective rotor blade pitch than the rear rotor systems until the desired inclination is achieved. Simultaneously, the floating masts of the rotor systems undergo an opposing tilt to ensure that the quadcopter80stays substantially at the same position over the inclined landing area and doesn't fly backwards.FIG.56shows the quadcopter80landed on the inclined landing area.

FIG.57toFIG.59show landing the quadcopter80on a landing area on a sea-based vehicle88which even under relatively calm conditions may lead to the landing area having a continuously changing inclination in at least one axis and generally two axes. The sea-based vehicle88includes telemetry apparatus89for real-time measuring its inclination details and transmitting same to the quadcopter80for enabling its safe substantially vertical descent on the landing area. Such real-time inclination details can supplement on-board ACAS functionality or replace same.FIG.57shows the quadcopter80hovering above the sea-based vehicle88.FIG.58shows the quadcopter80continuously adjusting its fuselage81's inclination to correspondingly match the sea-based vehicle88's continuously changing inclination. Continuously matching the fuselage81's inclination to the sea-based vehicle88's continuously changing inclination until landing involves continuous control of rpm and/or collective rotor blade pitch and simultaneous tilt control of the quadcopter's floating masts to counter lateral displacements.FIG.59shows the quadcopter80landed on the sea-based vehicle88.

Section 6: Technical Benefits of Rotorcraft with Forward Propulsion Unit and One or More Floating Masts

Rotorcraft with a forward propulsion unit and one or more floating masts have considerable technical benefits compared to conventional rotorcraft as summarized in the following table indicating a two-level grading system: Good and Medium. For illustrative purposes, rotorcraft with a forward propulsion unit and one or more floating masts are compared to a helicopter, a gyrodyne, a hybrid gyrodyne aircraft as disclosed in U.S. Pat. No. 10,046,853 to Vander Mey (hereinafter referred to as US '853 gyrodyne) and a VTOL rotorcraft as described in EP 2 990 332 A1 hereinafter referred to as EP '332 rotorcraft)

Flight Redundancy

Rotorcraft of the present invention have flight redundancy capability for cruising flight at a non-descending altitude, and also during climbing and descending. In case of power failure of one or more electric rotor motors, a FCS can control a rotorcraft by virtue of cyclic rotor blade pitch control. Conversely, in case of a power failure of a forward propulsion unit, a FCS can drive electric rotor motors to fly a rotorcraft of the present invention.

None of the helicopter, the gyrodyne, the US '853 gyrodyne, and the EP '332 rotorcraft has such flight redundancy capability. The helicopter and the EP '332 rotorcraft do not have a forward propulsion unit for providing forward thrust. The gyrodyne requires its one or more forward propulsion units for cruising flight, climbing, descending and hovering. The US '853 gyrodyne requires its protors for steering during cruising flight, climbing, descending and hovering.

Rotor System Redundancy

Rotorcraft of the present invention are controllable on the condition that at least one rotor system has a controllable cyclic rotor blade pitch. Accordingly, in the case of a rotorcraft with at least three rotor systems having at least two rotor systems with cyclic rotor blade pitch functionality, even if one of the rotor systems with cyclic rotor blade pitch functionality becomes inoperative, the rotorcraft can still be controlled and complete its flight to safe landing.

The EP '332 rotorcraft also has rotor system redundancy but the gyrodyne and US '853 gyrodyne do not have adjustable cyclic rotor blade pitch and therefore do not have rotor system redundancy

Cruising Energy Consumption

Maximum energy efficiency is achieved at a lowest platform angle of attack relative to air flow as possible by virtue of reducing total drag to a minimum. Rotorcraft of the present invention employs a forward propulsion unit for cruising and therefore can cruise at a low platform angle of attack relative to air flow.

In comparison to conventional rotorcraft, the present invention has comparable energy consumption to a gyrodyne and the US '853 gyrodyne during cruising. The former three have improved energy consumption relative to a helicopter and the EP '332 rotorcraft because the latter two do not have a forward propulsion unit and therefore require a higher platform angle of attack relative to air flow.

Maximum Flight Speed Vne

Maximum flight speed Vne is limited by stalling of a retreating rotor blade. Stalling occurs at a rotor blade's high angle of attack relative to air flow. Rotorcraft of the present invention gain air speed by increasing a forward propulsion unit's thrust rather than by forward cyclic rotor blade pitch thereby avoiding a high angle of attack of a retreating rotor blade.

In comparison to conventional rotorcraft, rotorcraft of the present invention have a maximum flight speed Vne comparable a gyrodyne and the US '853 gyrodyne. The former three have a higher maximum flight speed than a helicopter and the EP '332 rotorcraft because the latter two do not include a forward propulsion unit.

Operational Weather Limitation

Maneuverability of rotorcraft of the present invention depends on how many of their rotor systems enable individual or simultaneous adjustment of collective rotor blade pitch and cyclic rotor blade pitch. The greater the number of swashplate mechanisms the greater the maneuverability. The present invention is equally steerable when hovering and cruising at a non-descending altitude, and also when climbing and descending. The present invention's steering can be further improved by provision of vectored thrust means.

Present invention having multiple swashplate mechanisms: Grade Good

In comparison to conventional rotorcraft, the present invention has comparable maneuverability to the EP '332 rotorcraft. The former two are more maneuverable than a helicopter and a gyrodyne because the latter two have a single rotor system and are restricted to using their cyclic rotor blade pitch for rotorcraft roll and rotorcraft pitch. The former two are more maneuverable than the US '853 gyrodyne because the latter omits cyclic rotor blade pitch control.

Safe Emergency Landing

In case of power failures of both all electric rotor motors and the forward propulsion unit, full steering capability is maintained by virtue of at least one rotor system having a controllable cyclic rotor blade pitch. Safe emergency landings require both steering and autorotation. The present invention includes at least three rotor systems, at least one swashplate mechanism or alternative mechanism for enabling controllable cyclic rotor blade pitch of at least one rotor system, a forward propulsion unit, and preferably at least one freewheel arrangement.

In case the present invention does not include at least one freewheel arrangement, the present invention maintains steering and autorotation similar to the EP '332 rotorcraft and descends at a similar steep descent rate. The US '853 gyrodyne has a limited steering capability because it does not include swashplate mechanisms and also descends at a steep descent rate.

In case the present invention includes at least one freewheel arrangement, the present invention is capable of a safe emergency landing at a shallow descent rate similar to a helicopter and a gyrodyne.

Landing on Stationary Inclined Landing Area

A rotorcraft of the present invention is capable of a general vertical descent to land on a stationary inclined landing area by virtue of inclining its fuselage to be substantially parallel thereto without substantial horizontal movement relative to its generally vertical descent. In contradistinction, altering orientation of a conventional rotorcraft such that its fuselage is substantially parallel to a stationary inclined landing area, necessarily causes an undesirable horizontal movement due to a required change in its thrust vector.

Landing on Landing Area Having Continuously Changing Inclination

A rotorcraft of the present invention is capable of a general vertical descent to land on a landing area having a continuously changing inclination in at least one axis in a similar manner to landing on a stationary inclined landing area except that in this case the inclination of its fuselage is continuously changing to match the landing area's continuously changing inclination.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications, and other applications of the invention can be made within the scope of the appended claims.