Shifting a center of gravity of an aircraft

According to one aspect of the present disclosure, an apparatus for shifting a center of gravity of an aircraft is disclosed. The apparatus includes a propulsion component, a moveable ballast component, and an assembly configured to translate the moveable ballast component. The propulsion component is configured to assist in transitioning the aircraft between a first mobility phase and a second mobility phase. The assembly is configured to translate the moveable ballast component between an aft position and a forward position of the aircraft based on the aircraft transitioning between the first mobility phase and the second mobility phase to shift the center of gravity of the aircraft along a longitudinal axis of the aircraft.

FIELD

The present disclosure relates generally to the field of aircraft, and more specifically to shifting a center of gravity of an aircraft based on a change in mobility phase of the aircraft.

BACKGROUND

In different types of aircraft, the desired location of the aircraft's center of gravity —i.e., a balance location of the aircraft's mass, may depend on a variety of factors including a mobility phase in which the aircraft is operating. As one example, for an aircraft designed to operate in a hover mobility phase (e.g., a helicopter), a center of gravity of the aircraft is preferably collocated with a center of lift of the aircraft—i.e., a balance location of the aircraft's vertical thrust that enables hovering. By collocating the center of gravity with the center of lift, a load of the aircraft is equally balanced between all propulsors (e.g., rotors) of the aircraft, and the aircraft is able to provide power-efficient hovering without any one propulsor being loaded more than any other propulsor.

As another example, for an aircraft designed to operate primarily in a cruising mobility phase (e.g., a passenger jet), a center of gravity of the aircraft is preferably positioned forward in a longitudinal direction from a center of pressure of the aircraft—i.e., a balance location of upward aerodynamic loads on the aircraft in forward cruise flight. By positioning the center of gravity ahead of the center of pressure, positive static stability (i.e., static margin) is achieved while in the cruising mobility phase. Accordingly, the balance of aircraft mass and aerodynamic forces in a statically stable aircraft operates to passively reject small disturbances to pitch, thereby increasing stability and efficiency per flight phase.

SUMMARY

According to one aspect of the present disclosure, an apparatus for shifting a center of gravity of an aircraft is disclosed. The apparatus includes a propulsion component, a moveable ballast component, and an assembly configured to translate the moveable ballast component. The propulsion component is configured to assist in transitioning the aircraft between a first mobility phase and a second mobility phase. The assembly is configured to translate the moveable ballast component between an aft position and a forward position of the aircraft based on the aircraft transitioning between the first mobility phase and the second mobility phase to shift the center of gravity of the aircraft along a longitudinal axis of the aircraft.

DETAILED DESCRIPTION

Different aircraft may have differently positioned and fixed centers of gravity depending on the mobility phase in which the aircraft is designed to operate. Some aircraft are designed to transition between operation in different mobility phases, which can present issues when the center of gravity is misaligned for a particular mobility phase. For example, a vertical-take-off-and-landing (VTOL) aircraft may transition through a sequence of different mobility phases beginning with vertical takeoff, hover climb, hover, outbound transition, climb, cruise and maneuver, descent, inbound transition, hover and reserve, and vertical landing. In such a VTOL aircraft, if the center of gravity is fixed, then the aircraft is optimized for only some of the mobility phases and not the other mobility phases.

Thus, examples are disclosed that relate to shifting a center of gravity of an aircraft based on the aircraft transitioning from one mobility phase to another mobility phase. Such mobility phase-based shifting of the center of gravity allows for the center of gravity to be optimally positioned in the aircraft according to the particular mobility phase in which the aircraft is operating. As described in more detail below, the center of gravity of an aircraft can be shifted in different ways using a variety of different assemblies.

FIGS.1A,1B,2A, and2Bare diagrammatic representations of an exemplary embodiment of an aircraft100according to examples of the present disclosure. The aircraft100is an exemplary embodiment of a VTOL aircraft. The aircraft100is configured to operate in a hover mobility phase as shown inFIGS.1A and2A. For example, the aircraft100may operate in the hover mobility phase that includes vertical take-off, hover climb, hover, hover and reserve and vertical landing. Further, the aircraft100is configured to transition between operating in the hover mobility phase and operating in a cruising mobility phase as shown inFIGS.1B and2B. Note that aircraft100may operate in other intermediate mobility phases when transitioning between the hover phase and the cruising phase (e.g., outbound transition, inbound transition).

The aircraft100comprises a fuselage102, a pair of wings104(e.g.,104.1,104.2), a pair of tail fins106(e.g.,106.1,106.2) that embody an H-tail type empennage, a pair of booms108(e.g.,108.1,108.2), and a plurality of rotor propulsors110(e.g.,110.1-110.9). In various examples, such components of the aircraft100may be fabricated from metal, composite materials, polymeric materials, ceramic materials, and/or combinations thereof.

The fuselage102comprises an interior cabin112that is configured to accommodate a payload, such as one or more passengers and optionally cargo. In some examples, the fuselage102accommodates other components related to shifting a center of gravity of the aircraft100, as will be discussed in further detail below with reference toFIGS.3A and3B.

The pair of wings104and the pair of tail fins106are operatively coupled to the fuselage102and extend laterally from the fuselage102along a lateral axis200of the aircraft100(shown inFIGS.2A and2B). Note that the term “along” is not meant to limit the positioning of the wing and tail fins to only on the lateral axis of the aircraft. Rather, the wing and tail fins can be positioned on, beside, over, or parallel to the lateral axis of the aircraft without departing from the scope of the present description. The pair of wings104and the pair of tail fins106are configured to provide lift and stability while the aircraft100is moving in a forward flight direction in the cruising mobility phase. The pair of booms108are operatively coupled to the fuselage102and extend parallel to a longitudinal axis202of the aircraft100(shown inFIGS.2A and2B).

A plurality of propulsion components in the form of rotor propulsors110.1-110.8are distributed along each boom108. In this example, the rotor propulsors110.1,110.2,110.3, and110.4are positioned on the boom108.1and the rotor propulsors110.5,110.6,110.7, and110.8are positioned on the boom108.2. These rotor propulsors are configured to direct thrust downward relative to the fuselage102while the aircraft100is operating in the hover mobility phase. The positioning of the rotor propulsors110on the booms108may be selected to accommodate various design and flight dynamics considerations.

In the present example, a propulsion component in the form of a pusher rotor propulsor110.9is operatively coupled to a tail end of the fuselage102. The pusher rotor propulsor110.9is configured to direct thrust rearward relative to the fuselage102when the aircraft100is operating in the cruising mobility phase. In some examples, the pusher rotor propulsor110.9may assist in transitioning the aircraft100between the hover mobility phase and the cruising mobility phase by directing thrust rearward.

The pusher rotor propulsor110.9can be controlled to have any suitable rotational speed to assist in transitioning the aircraft100between the hover mobility phase and the cruising mobility phase. In some examples, the pusher rotor propulsor110.9may not rotate at all when the aircraft100is operating in the hover mobility phase. In other examples, the pusher rotor propulsor110.9may rotate at a same or lesser speed than the other rotor propulsors110positioned on the booms108when the aircraft100is operating in the hover mobility phase. Correspondingly, in some examples, the pusher rotor propulsor110.9may rotate at a same or greater speed than the rotor propulsors110positioned on the booms108when the aircraft100is operating in the cruising mobility phase.

Additionally, the rotor propulsors110.1and110.5positioned on respective front ends of the booms108are configured to assist in transitioning the aircraft100between the hover mobility phase and the cruising mobility phase. In particular, in the illustrated embodiment, the rotor propulsors110.1and110.5are configured as tilting rotor propulsors that each pivot between an upright position in the hover mobility phase (as shown inFIGS.1A and2A) and a prone position in the cruising mobility phase (as shown inFIGS.1B and2B). In the upright position, the tilting rotor propulsors110.1and110.5provide upward thrust. In the prone position, the tilting rotor propulsors110.1and110.5provide forward or rearward thrust. During the transition between the upright position and prone position, the amount of tilt of the rotor propulsors between the upright position and the prone position controls the direction of the force (i.e. thrust) during the transition to balance and maneuver the aircraft between hover and forward cruising.

The plurality of rotor propulsors110may utilize any suitable type of engine, motor or other power generation mechanism. In some examples, the rotor propulsors110may include internal combustion engines. In other examples, the rotor propulsors110may include electric motors. In still other examples, the rotor propulsors110may include mechanical or electromechanical engines. While each boom is illustrated as having four rotor propulsors, it will be appreciated that each boom may include a greater or lesser number of rotor propulsors to achieve a desired function, such as achieving particular thrust and/or balance requirements. In some embodiments, the booms108, the forwardly positioned rotor propulsors110.1and110.5, and/or the pusher propulsor110.9may be omitted from the aircraft100. In some embodiments, the forwardly positioned rotor propulsors110.1and110.5may be fixed in either the upright or prone position. In some embodiments, the aircraft100may include additional or alternative propulsion components, such as turbine engines. The aircraft100may include any suitable propulsion components to achieve VTOL capability.

As described in more detail below, to enable shifting the center of gravity204of the aircraft100, a pair of moveable ballast components114.1and114.2are provided within the booms108.1and108.2, respectively. Each of the moveable ballast components114are configured to translate linearly within the associated boom along the longitudinal axis202(shown inFIGS.2A and2B) of the aircraft100between an aft position (shown inFIGS.1A and2A) and a forward position (shown inFIGS.1B and2B) based on the aircraft100transitioning between the hover mobility phase and the cruising mobility phase. Note that the term “along” is not meant to limit the translation of the moveable ballast components114to only on the longitudinal axis of the aircraft. Rather, the moveable ballast components114can move on, beside, over, or parallel to the longitudinal axis of the aircraft without departing from the scope of the present description. Further, the movement of the pair of moveable ballast components114is configured to shift the position of the center of gravity204of the aircraft100linearly on the longitudinal axis202, while not changing the center of gravity relative to the lateral axis200of the aircraft100. In other words, the pair of moveable ballast components114may be substantially balanced to laterally align the center of gravity204with the longitudinal axis202.

In some embodiments, the linear movement of the moveable ballast components114may be mechanically coupled to the pivoting/tilting motion of the tilt rotors110.1and110.5, such that pivoting the tilt rotors110.1and110.5between the upright and prone positions causes the moveable ballast components114to translate linearly between the aft and forward positions within the booms108. In other embodiments and as described in more detail below, the linear movement of the moveable ballast components114is not mechanically coupled to the pivoting motion of the tilt rotors110.1and110.5. In these examples, the moveable ballast components114are translated using a separate translation assembly that is controlled in conjunction with pivoting the tilt rotors110.1and110.5.

As shown inFIG.2A, in the illustrated embodiment, when the aircraft100is in the hover mobility phase where the moveable ballast components114are in the aft position, the center of gravity204of the aircraft100is positioned proximate to a center of lift206of the aircraft100and in substantial alignment with the lateral axis200and the longitudinal axis202. Also, the center of gravity204and the center of lift206are positioned slightly ahead of a center of pressure208of the aircraft100. As shown inFIG.2B, based on the aircraft100transitioning from the hover mobility phase to the cruise mobility phase, the moveable ballast components114are translated from the aft position toward a forward position to shift the center of gravity204of the aircraft forward. Meanwhile, the center of lift206and the center of pressure208remain in substantially the same position as when the aircraft100is in the hover mobility phase.

In a similar manner, when the aircraft100transitions from the cruising mobility phase to the hover phase, the moveable ballast components114are translated from the forward position (FIG.2B) toward the aft position (FIG.2A) based on this transition. In different examples and flight operations, the center of gravity204may be shifted laterally along the longitudinal axis202of the aircraft100by any suitable amount to optimize the flight dynamics of the particular mobility phase in which the aircraft is operating.

The pair of moveable ballast components114may take any suitable form. In some embodiments, the moveable ballast components114may comprise a power storage component configured to provide electrical power to one or more other components, such as one or more of the propulsion components of the aircraft100. In some examples, a power storage component may comprise a battery or other electrical power storage device.

In other embodiments where the aircraft comprises combustion engines, the moveable ballast component may comprise a fuel tank. Further, in some embodiments, the aircraft may include multiple fuel tanks dispersed along the longitudinal axis of the aircraft, and fuel may be transferred from one fuel tank to another fuel tank to shift the center of gravity based on the aircraft transitioning from one mobility phase to another mobility phase. In still other embodiments, passengers and/or associated accommodations may be used as moveable ballast components. As one example, seats in a cabin may be translated forward or aft based on a transition from one mobility phase to another mobility phase.

The aircraft may include any suitable number of moveable ballast components that can have any suitable number of translation paths in order to shift the center of gravity along the longitudinal axis of the aircraft based on the aircraft transitioning between mobility phases.

Additionally or alternatively, in some embodiments, one or more moveable ballast components may be located within a fuselage of the aircraft.FIGS.3A and3Bdiagrammatically represent an exemplary embodiment of an aircraft300comprising a fuselage302. The fuselage302comprises an interior cabin304configured to accommodate passengers, and a compartment306positioned below the interior cabin304. The compartment306contains a moveable ballast component308configured to move linearly between an aft position (shown inFIG.3A) and a forward position (shown inFIG.3B) to shift a center of gravity320of the aircraft300based on the aircraft transitioning between different mobility phases.

The moveable ballast component308may take any suitable form. The moveable ballast component308is translated along a longitudinal axis310of the aircraft300by a translation assembly312. The translation assembly312may comprise any suitable mechanism that is configured to push/pull or otherwise move the moveable ballast component308between the aft and forward positions based on the aircraft transitioning between different mobility phases. As one example, the translation assembly312comprises a linear actuator, such as a servo motor that allows for precise control of the linear position of the moveable ballast component308. The translation assembly312is controlled by a controller314. In some examples, the translation assembly312and the controller314may be collectively referred to as a control system. In operation, the controller314is configured to dynamically control the translation assembly312to translate the moveable ballast component308along the longitudinal axis310of the aircraft300based on the aircraft300transitioning from one mobility phase to another mobility phase.

The controller314may control the translation assembly312to translate the moveable ballast component308based on the aircraft300transitioning from one mobility phase to another mobility phase in relation to the aerodynamic centers of the aircraft100(i.e., center of lift/pressure). The controller314may translate the moveable ballast component308within a window of time having any suitable temporal relationship with the transition between mobility phases. In some examples, the controller314may control the translation assembly312to translate the moveable ballast component308during a window of time when the aircraft300transitions between mobility phases. As one example, the moveable ballast component308may be translated from the aft position to the forward position as the tilt rotors of the aircraft pivot from the upright position to the prone position causing the aircraft300to transition from the hover mobility phase to the cruising mobility phase. In other examples, the controller314may control the translation assembly312to translate the moveable ballast component308based on the aircraft300transitioning between mobility phases during a window of time before or after the aircraft300transitions between mobility phases. For example, the moveable ballast component308may be translated from the aft position to the forward position after the tilt rotors pivot from the upright position to the prone position.

In some embodiments, the controller314is configured to control the propulsion components of the aircraft300to transition the aircraft300from one mobility phase to another mobility phase, such that the controller314controls both the propulsion components and translation of the moveable ballast component308in a coordinated fashion. In other embodiments, the controller314is configured to receive an indication that the aircraft300is transitioning from one mobility phase to another mobility phase, and to correspondingly control the translation of the moveable ballast component308responsive to receiving the indication. For example, such an indication may be provided by a sensor or another controller of the aircraft.

The controller314includes one or more processors communicatively coupled with one or more memory devices. The one or more processors are configured to execute instructions stored in the one or more memory devices. For example, the one or more processors may be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. The one or more processors may be configured to execute software instructions. Additionally, or alternatively, the one or more processors may be configured to execute hardware or firmware instructions. The one or more processors may be single-core or multi-core, and the instructions executed thereon may be configured for sequential, parallel, and/or distributed processing. The one or more storage devices may include volatile, nonvolatile, dynamic, static, read/write, read-only, random-access, sequential-access, location-addressable, file-addressable, and/or content-addressable devices. Aspects of the one or more processors and the one or more storage devices may be integrated together into one or more hardware-logic components. Such hardware-logic components may include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC/ASICs), program- and application-specific standard products (PSSP/ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

In the illustrated embodiment, the moveable ballast component308, the translation assembly312, and the controller314are located in the compartment306positioned below the interior cabin304. In other embodiments, the moveable ballast component308, the translation assembly312, and/or the controller314may be positioned in another suitable location within the fuselage. In some embodiments, the controller may be located in another portion of the aircraft, such as a wing or a boom.

In the illustrated embodiment, the moveable ballast component308is not mechanically coupled to a propulsion component of the aircraft300. Rather, the controller314controls the translation assembly312to translate the moveable ballast component308in coordination with the aircraft300transitioning form one mobility phase to another mobility phase. In other embodiments, the moveable ballast component may be mechanically coupled to a propulsion component of the aircraft.

FIGS.4A-4D,5A-5B,6A-6B,7A-7B,8A-8B, and9A-9Bare diagrammatic representations of different embodiments of mechanical assemblies that mechanically couple a moveable ballast component to a moveable propulsion component, such that rotary/pivoting movement of the moveable propulsion component is tied to linear translation of the moveable ballast component. In different examples, the herein described mechanical assemblies are mounted to a fixed component of an aircraft. The mechanical assemblies may be utilized with any suitable aircraft. Regarding the example aircraft100shown inFIGS.1A,1B,2A, and2B, such mechanical assemblies can be mounted internally or externally to one of the booms108of the aircraft. In some examples, one of the mechanical assemblies may be mounted on a surface of one of the booms108. In other examples, one of the mechanical assemblies may be at least partially contained within one of the booms108. The mechanical assemblies may be mounted to any suitable component of an aircraft. Moreover, any suitable number of such mechanical assemblies may be employed in the aircraft. For example, one or more instances of the mechanical assemblies may be mounted to each of the booms108of the aircraft100.

FIGS.4A-4Dare diagrammatic representations of an exemplary embodiment of an apparatus400comprising a four-bar linkage402for shifting a center of gravity of an aircraft. The four-bar linkage402is mounted to a fixed component404of an aircraft. A tilting rotor propulsor406is mounted on a forward end408of the four-bar linkage402. A moveable ballast component410is mounted to the upper horizontal bar416proximate to an aft end412of the four-bar linkage402opposite the forward end408. The moveable ballast component410may take any suitable form as described above. As one example, the moveable ballast component410comprises a battery configured to provide power to the tilting rotor propulsor406. In some embodiments, the moveable ballast component410may comprise an aerodynamic fairing.

The four-bar linkage402comprises a plurality of bars coupled together via a plurality of corresponding revolute joints. The four-bar linkage402is configured to transition between an upright position shown in the side view ofFIG.4Aand top view ofFIG.4B, and a prone position shown in the side view ofFIG.4Cand the top view ofFIG.4D. In the upright position ofFIGS.4A and4B, the tilting rotor propulsor406can provide upward or downward thrust for a hover mobility phase of the aircraft. In this upright position, the moveable ballast component410assumes an aft position that aligns a center of gravity of the aircraft with a center of hover of the aircraft.

The four-bar linkage402transitions from the upright position to the prone position ofFIGS.4C and4Dby rotating the shorter bars of the four-bar linkage from a vertical orientation to a horizontal orientation. Such rotation of the shorter bars of the four-bar linkage402causes the tilting rotor propulsor406to pivot from the upright position to a forward-facing prone position shown inFIGS.4C and4D. In the prone position, the tilting rotor propulsor406can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, such rotation of the shorter bars of the four-bar linkage402causes the moveable ballast component410to translate along a longitudinal axis420of the aircraft from the aft position to a forward position, which causes the center of gravity (CG) of the aircraft to shift forward (i.e., leftward on the page). In other words, the pivoting motion of the tilt rotor propulsor406is mechanically coupled to the linear motion of the moveable ballast component410along the longitudinal axis420via the four-bar linkage402.

FIGS.5A-5Bare diagrammatic representations of an exemplary embodiment of an apparatus500for shifting a center of gravity of an aircraft comprising a slider crank mechanism502. The apparatus500is mounted to a fixed component504of an aircraft. A tilting rotor propulsor506is mounted on a forward end508of the slider crank mechanism502. A moveable ballast component510is mounted proximate to an aft end512of the slider crank mechanism502opposite the forward end508.

The slider crank mechanism502comprises a plurality of bars coupled together via a plurality of corresponding revolute joints and a rocker joint514coupled to a rocker arm516. The rocker joint514is configured to rotate and is translationally fixed. The slider crank mechanism502is configured to transition the between an upright position shown inFIG.5Aand a prone position shown inFIG.5B.

In the upright position, the tilting rotor propulsor506and the rocker arm516assume an upright position, such that the tilting rotor propulsor506can provide upward or downward thrust for a hover mobility phase of the aircraft. In the upright position, the moveable ballast component510is positioned in an aft position that aligns a center of gravity of the aircraft with a center of hover of the aircraft. The slider crank mechanism502transitions from the upright position to the prone position ofFIG.5Bby rotating the rocker arm516forward about the rocker joint514such that rocker arm pivots from a vertical position to the prone position. Such rotation of the rocker arm516causes the tilting rotor propulsor506to pivot from the upright position to a forward-facing prone position. In the prone position shown inFIG.5B, the tilting rotor propulsor506can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, such rotation of the rocker arm516causes the moveable ballast component510to translate along a longitudinal axis520of the aircraft from the aft position to a forward position via the slider crank mechanism502, which causes the center of gravity (CG) of the aircraft to shift forward (i.e., leftward on the page). In other words, the pivoting motion of the tilting rotor propulsor506is mechanically coupled to the linear motion of the moveable ballast component510along the longitudinal axis520via the slider crank mechanism502.

FIGS.6A-6Bare diagrammatic representations of an exemplary embodiment of an apparatus600for shifting a center of gravity of an aircraft comprising a chain and sprocket mechanism602. The apparatus600is mounted to a fixed component604of an aircraft. A tilting rotor propulsor606is mounted to chain616on a forward end608of the chain and sprocket mechanism602. A moveable ballast component610is mounted to an upper portion of chain616proximate to an aft end612of the chain and sprocket mechanism602that is opposite the forward end608.

The chain and sprocket mechanism602comprises a pair of sprockets614.1and614.2and a chain616wrapped around the pair of sprockets. The chain and sprocket mechanism602is configured to transition the tilting rotor propulsor606between an upright position shown inFIG.6Aand a prone position shown inFIG.6B. In the upright position, the tilting rotor propulsor606can provide upward or downward thrust for a hover mobility phase of the aircraft. In the upright position ofFIG.6A, the moveable ballast component610is located in an aft position that aligns a center of gravity of the aircraft with a center of hover of the aircraft.

The chain and sprocket mechanism602transitions the tilting rotor propulsor606from the upright position to the prone position by rotating the pair of sprockets614.1and614.2in a counter-clockwise direction that causes the upper portion of chain616to translate along the longitudinal axis620of the aircraft. Such translation of the chain616causes the tilting rotor propulsor606to pivot from the upright position to a forward-facing prone position shown inFIG.6B. In the prone position, the tilting rotor propulsor606can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, such translation of the chain616causes the moveable ballast component610to translate linearly from the aft position to a forward position via the chain and sprocket mechanism602, which causes the center of gravity (CG) of the aircraft to shift forward (i.e., leftward on the page). In other words, the pivoting motion of the tilting rotor propulsor606is mechanically coupled to the linear motion of the moveable ballast component610via the chain and sprocket mechanism602.

FIGS.7A-7Bare diagrammatic representations of an exemplary embodiment of an apparatus700for shifting a center of gravity of an aircraft comprising a rack gear drive mechanism702. Portions of the apparatus700are mounted to a fixed component704of an aircraft. A tilting rotor propulsor706is mounted on a forward end708of the rack gear drive mechanism702. A moveable ballast component710is mounted to a moveable rack718proximate to an aft end712of the rack gear drive mechanism702opposite the forward end708.

The rack gear drive mechanism702comprises a fixed rack714, a gear716, a moveable rack718, a rod720, a crank722, and a drive shaft724. The rack gear drive mechanism702is configured to transition between an upright position shown inFIG.7Aand a prone position shown inFIG.7B. In the upright position, the tilting rotor propulsor706assumes an upright position on the drive shaft724, such that the tilting rotor propulsor706can provide upward or downward thrust for a hover mobility phase of the aircraft. In the upright position, the moveable ballast component710and moveable rack718are located in an aft position that aligns a center of gravity of the aircraft with a center of hover of the aircraft.

The rack gear drive mechanism702transitions from the upright position to the prone position by rotating the drive shaft724causing the crank722to rotate and translate the rod720in the X-axis direction. Translation of the rod720correspondingly causes translation and rotation of the gear716and translation of the moveable rack718. Such rotation of the drive shaft724causes the tilting rotor propulsor706to pivot from the upright position to a forward-facing prone position. In the prone position, the tilting rotor propulsor706can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, such translation of the moveable rack718causes the moveable ballast component710to translate linearly from the aft position to a forward position via the rack gear drive mechanism702, which causes the center of gravity (CG) of the aircraft to shift forward (i.e., leftward on the page). In other words, the pivoting motion of the tilting rotor propulsor706is mechanically coupled to the linear motion of the moveable ballast component710along the longitudinal axis726of the aircraft via the rack gear drive mechanism702. Note that the rack gear drive mechanism702provides a stroke-doubling mechanism that advantageously yields a larger translation range of the center of gravity if such a range is desired.

FIGS.8A-8Bare diagrammatic representations of an exemplary embodiment of an apparatus800for shifting a center of gravity of an aircraft comprising a tilting rotor mechanism802. The apparatus800is mounted to a fixed component804of an aircraft. A tilting rotor propulsor806is mounted on a distal end of a shaft808. Shaft808is rotatably coupled to a stanchion816that extends from the fixed component804. A moveable ballast component810is mounted intermediate the tilting rotor propulsor806and a pivot812that rotatably couples the shaft808to the stanchion812.

The tilting rotor mechanism802is configured to transition between an upright position shown inFIG.8Aand a prone position shown inFIG.8B. In the upright position, the shaft808assumes an upwardly-extending position substantially collinear with the stanchion812, such that the tilting rotor propulsor806can provide upward or downward thrust for a hover mobility phase of the aircraft. The tilting rotor mechanism802transitions from the upright position to the prone position by rotating shaft808about the pivot812to cause corresponding rotation of the tilting rotor propulsor806and the moveable ballast component810.

Such rotation about the pivot812causes the tilting rotor propulsor806to pivot from the upright position to a forward-facing prone position. In the prone position, the tilting rotor propulsor806can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, such rotation about the pivot812causes the moveable ballast component810to not only rotate but also translate linearly forward direction along the longitudinal axis820of the aircraft, which causes the center of gravity (CG) of the aircraft to also shift forward (i.e., leftward on the page). In other words, the rotary motion of the propulsor about pivot812causes corresponding motion of the moveable ballast component810via the tilting rotor mechanism802. In embodiments where the moveable ballast component810is a battery that provides power to the tilt rotor propulsor, the tilting rotor mechanism has the added benefit of reduced power harness mass, since the battery is in close proximity to the rotor propulsor being driven by the battery.

FIGS.9A-9Bare diagrammatic representations of an exemplary embodiment of an apparatus900for shifting a center of gravity of an aircraft comprising a tilt wing mechanism902. A rotor propulsor904is mounted on a leading edge of a wing906in a fixed position relative to the wing906(i.e., the rotor propulsor904does not tilt relative to the wing906). A moveable ballast component908is mounted within the wing906intermediate the rotor propulsor904and a pivot910.

The tilt wing mechanism902is configured to transition between an upright position shown inFIG.9Aand a prone position shown inFIG.9B. In the upright position, the rotor propulsor904can provide upward or downward thrust for a hover mobility phase of the aircraft. The tilt wing mechanism902transitions from the upright position to the prone position by rotating about the pivot910causing rotation of the wing906, and correspondingly rotation of the rotor propulsor904and the moveable ballast component908. Such rotation of the wing906causes the rotor propulsor904to rotate from the upright position to a forward-facing prone position. In the prone position, the rotor propulsor906can provide forward or rearward thrust for a cruising mobility phase of the aircraft. Additionally, since the movable ballast component908is positioned intermediate the leading edge of the wing906and the pivot910, such rotation about the pivot910causes the moveable ballast component910to not only rotate but also translate linearly in the X-axis direction along the longitudinal axis920of the aircraft, which causes the center of gravity (CG) of the aircraft to also shift forward (i.e., leftward on the page). In other words, the rotary motion of the wing906about pivot910causes corresponding motion of the moveable ballast component908via the tilt wing mechanism902. In embodiments where the moveable ballast component908is a battery providing power to the rotor propulsor904, the tilt wing mechanism902has the added benefit of reduced power harness mass, since the battery is in close proximity to the rotor propulsor being driven by the battery.

The above described apparatuses provide different variable geometry mechanisms to change the center of gravity of an aircraft. Such variable geometry mechanisms mechanically couple translational movement of a moveable ballast component to rotary movement of tilting rotor propulsors or wings of the aircraft. In this way, the center of gravity of the aircraft automatically shifts as the rotor propulsors tilt for the different mobility phases. Such mechanisms can be linked to single rotor propulsors, and thus can be redundant in multi-rotor propulsor embodiments to increase error tolerance of an aircraft.

FIG.10is a flowchart of an example method1000of shifting a center of gravity of an aircraft. For example, the method1000may be performed by the controller314shown inFIGS.3A and3B.

At1002, the method1000includes providing a propulsion component in an aircraft. The propulsion component may take any suitable form. In some examples, the propulsion component includes a tilting rotor configured to move between an upright position and a prone position. In some examples, the tilting rotor is fixed to a tilt wing of the aircraft. In other examples, the tilting rotor is not fixed to a wing of the aircraft. The propulsion component is configured to assist in transitioning the aircraft between a first mobility phase and a second mobility phase. For example, the first mobility phase may include a hover (or vertical takeoff or vertical landing) phase and the second mobility phase may include a cruising phase.

At1004, the method1000includes providing a moveable ballast component in the aircraft. The moveable ballast component is configured to move along a longitudinal axis of the aircraft between an aft position and a forward position of the aircraft to shift the center of gravity of the aircraft. For example, the moveable ballast component may include a power storage component configured to provide power to the propulsion component. As one example, the power storage component may include a battery. As another example, the power storage component may include liquid or solid fuel that may be combusted or otherwise consumed to provide power to the propulsion component.

At1006, the method1000includes transitioning the aircraft from the first mobility phase to the second mobility phase. At1008, the method1000includes, based on transitioning the aircraft from the first mobility phase to the second mobility phase, moving the moveable ballast component from the aft position toward the forward position to shift the center of gravity of the aircraft along the longitudinal axis of the aircraft.

In some embodiments, the aircraft may include an assembly configured to translate the moveable ballast component to shift the center of gravity of the aircraft along a longitudinal axis of the aircraft between the aft position and the forward position of the aircraft. The aircraft may include any suitable assembly to translate the ballast component to shift the center of gravity of the aircraft along the longitudinal axis of the aircraft. For example, the assembly may include a rack gear drive mechanism, a chain and sprocket mechanism, a slider crank mechanism, or a four-bar linkage.

At1010, the method1000includes transitioning the aircraft from the second mobility phase to the first mobility phase. At1012, the method1000includes, based on transitioning the aircraft from the second mobility phase to the first mobility phase, moving the moveable ballast component from the forward position toward the aft position to shift the center of gravity of the aircraft along the longitudinal axis of the aircraft.

The concepts described herein are broadly applicable to any suitable type of aircraft, including VTOL aircraft with or without fixed wings, and manned and unmanned aircraft. Additionally, the concepts described herein may be broadly applicable to any suitable type of mobility phase of an aircraft beyond hover and cruising mobility phases.

The present disclosure includes all novel and non-obvious combinations and subcombinations of the various features and techniques disclosed herein. The various features and techniques disclosed herein are not necessarily required of all examples of the present disclosure. Furthermore, the various features and techniques disclosed herein may define patentable subject matter apart from the disclosed examples and may find utility in other implementations not expressly disclosed herein.