Patent Description:
An electric vertical takeoff and landing (eVTOL) is a type of aircraft that uses electric power to supply rotational energy in an aircraft propulsion system for enabling the aircraft to hover, take off, and land vertically. Because of their versatility and lack of a need for a runway, eVTOLs are particularly useful for providing urban air mobility. As used herein, the term eVTOL also includes VTOLs that use hybrid electric propulsion systems. One particular type of eVTOL is an electric tiltrotor aircraft.

<CIT> describes a tiltrotor aircraft having a vertical takeoff and landing (VTOL) flight mode and a forward flight mode, the aircraft comprising tiltable rotors located at forward boom ends, tiltable ducted fans located at wings aft of the forward boom ends, and aft rotors located on aft boom portions.

<CIT> describes air vehicle having an airframe, aerodynamic lift generating wings, and a propulsion system. The propulsion system provides propulsion to the air vehicle in powered aerodynamic flight mode and in vectored flight mode, and stability and control in vectored flight mode.

<CIT> describes a tiltrotor aircraft having a vertical takeoff and landing flight mode and a forward flight mode. The tiltrotor aircraft includes a longitudinally extending fuselage with a wing extending laterally therefrom having oppositely disposed wing tips distal from the fuselage. Tip booms respectively extend longitudinally from the wing tips. Forward rotors are coupled to the forward ends of the tip booms.

<CIT> describes a system and method for providing propulsion and control to an air vehicle, and for operating the vehicle, including at least three propulsion units that provide vertical thrust for vectored thrust flight, in which at least one or two of the propulsion units also provide thrust for vectored thrust cruising or aerodynamic flight by suitably tilting the respective propulsion units for changing the thrust vector thereof.

According to a first aspect of the invention, there is provided an aircraft according to claim <NUM>.

Optional and/or preferable features are set out in the dependent claims.

To provide a more complete understanding of the present disclosure and features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying figures, in which like reference numerals represent like elements:.

The following disclosure describes various illustrative embodiments and examples for implementing the features and functionality of the present disclosure. While particular components, arrangements, and/or features are described below in connection with various example embodiments, these are merely examples used to simplify the present disclosure and are not intended to be limiting. It will of course be appreciated that in the development of any actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, including compliance with system, business, and/or legal constraints, which may vary from one implementation to another. Moreover, it will be appreciated that, while such a development effort might be complex and time-consuming; it would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the Specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, components, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as "above", "below", "upper", "lower", "top", "bottom", or other similar terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components, should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the components described herein may be oriented in any desired direction. When used to describe a range of dimensions or other characteristics (e.g., time, pressure, temperature, length, width, etc.) of an element, operations, and/or conditions, the phrase "between X and Y" represents a range that includes X and Y.

Additionally, as referred to herein in this Specification, the terms "forward", "aft", "inboard", and "outboard" may be used to describe relative relationship(s) between components and/or spatial orientation of aspect(s) of a component or components. The term "forward" may refer to a spatial direction that is closer to a front of an aircraft relative to another component or component aspect(s). The term "aft" may refer to a spatial direction that is closer to a rear of an aircraft relative to another component or component aspect(s). The term "inboard" may refer to a location of a component that is within the fuselage of an aircraft and/or a spatial direction that is closer to or along a centerline of the aircraft (wherein the centerline runs between the front and the rear of the aircraft) or other point of reference relative to another component or component aspect. The term "outboard" may refer to a location of a component that is outside the fuselage of an aircraft and/or a spatial direction that farther from the centerline of the aircraft or other point of reference relative to another component or component aspect.

Further, the present disclosure may repeat reference numerals and/or letters in the various examples. Example embodiments that may be used to implement the features and functionality of this disclosure will now be described with more particular reference to the accompanying FIGURES.

Electric tiltrotor aircraft configurations described herein are characterized by tilting of the rotors on a wing. In various embodiments, the tiltrotor aircraft configuration rotates the rotor pylon at the side pylon of body, wing station inboard on the wing, or incorporating tiltwing elements with wing rotation as a whole. The degree of wing rotation with the pylon and placement of the axis of rotation relative to the wing are unique elements of embodiments described herein. Rotating a greater portion of the wing with the pylon reduces download of the rotor on the wing but makes transition of the wing from hovering flight to airplane mode flight more difficult, as the rotated portion of the wing will be stalled through a lot of transition increasing rotor power required in transition beyond that required for hover. Variation of wing rotation includes rotating only the pylon and none of the wing which make transition benign but increase power required in a hover to the downwash on the horizontal wing surfaces, rotating an outboard wing extension with the pylon which is a good compromise of download reduction and benign transition, rotating an inboard section of the wing with the pylon which or rotating the whole wing with the pylon both of which increase transition power required from a conventional tiltrotor but reduce download in hover. Pylon rotation actuation is effected through linear or rotary actuators forward, aft, or under the pylon are described herein.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM>, not in accordance with the appended claims, that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wing <NUM>, and a tail assembly <NUM>. The aircraft further includes propulsion systems 112a, 112b, proximate outboard ends of wing <NUM>. Wing tips 114a, 114b, are fixedly connected to outboard sides of propulsion systems 112a, 112b, as will be described below.

Each propulsion system 112a, 112b, includes a drive system housing comprising a pylon 130a, 130b, and a rotatable open rotor assembly 132a, 132b, comprising a plurality of rotor blades 134a, 134b, connected to a rotor mast and configured to rotate about a rotor axis 136a, 136b. As shown in <FIG> and <FIG>, each rotor assembly 132a, 132b, includes three (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented. Rotation of rotor blades 134a, 134b, about rotor axis 136a, 136b, generates lift while operating in helicopter mode and thrust while operating in airplane mode. Each pylon 130a, 130b, may house one or more electric motors therein configured to produce rotational energy that drives the rotation of rotor assembly 132a, 132b. Alternatively, each pylon 130a, 130b, may house a gearbox therein that drives the rotation of rotor assembly 132a, 132b, wherein the gearbox receives rotational energy from a driveshaft.

As illustrated in <FIG> and <FIG>, wing tips 114a, 114b, are fixedly attached to outboard sides of pylons 130a, 130b. Inboard sides of pylons 130a, 130b, are tiltably connected to outboard ends of wing <NUM>. In operation, wing tips 114a, 114b, together with propulsion systems 112a, 112b, tilt relative to wing <NUM> between a first position (<FIG>), in which propulsion systems 112a, 112b, and wing tips 114a, 114b, are configured in a hover mode, and a second position (<FIG>), in which propulsion systems 112a, 112b, and wing tips 114a, 114b, are configured in a cruise mode.

The position of rotor assemblies 132a, 132b, as well as the pitch of individual rotor blades 134a, 134b, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, propulsion systems 112a, 112b, are each convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Propulsion systems 112a, 112b, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Propulsion systems 112a, 112b, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 112a, 112b, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Propulsion systems 112a, 112b, including wing tips 114a, 114b, may be tiltable between the vertical and horizontal positions by actuators (not shown) that are tiltable in response to commands originating from a pilot and/or a flight control system. Typically, linear actuators may be used, which attach to the wing tip via a spindle in the outboard tip ribs and attach to a clevis on the pylon support which forms the structure of the pylon. The dual or triply-redundant electric or hydraulic actuator extends pushing the pylon up greater than <NUM> degrees. A gimbal on the lower wing attach spindle allows the angle of the actuator to rotate as the pylon moves from horizontal to vertical. In a more compact installation, a rotary actuator could be used. The actuator would be installed at a radius about the pylon spindle such that movement of the rotary actuator about the radius would drive the pylon rotation. Each of the propulsion systems 112a, 112b, may utilize a drive system comprising one or more electric motors and gearbox unit disposed within a respective pylon 130a, 130b as a power source to rotate the respective rotor assembly 132a, 132b about rotor axis 136a, 136b via a rotor mast.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM>, not in accordance with the appended claims, that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wing <NUM> comprising wing segments 202a, 202b, tiltably connected to fuselage <NUM>, and a tail assembly <NUM>. The aircraft further includes propulsion systems 212a, 212b, integrated into respective wing segments 204a, 204b. Wing tips 214a, 214b, are fixedly connected to outboard sides of propulsion systems 212a, 212b.

Similar to the propulsion systems of aircraft <NUM>, each of propulsion systems 212a, 212b, may include a drive system housing comprising a pylon, and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, the rotor assembly of each of propulsion systems 212a, 212b, includes three (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented. Rotation of rotor assemblies of propulsion systems 212a, 212b, generates lift while the aircraft <NUM> is operating in helicopter mode and thrust while the aircraft <NUM> is operating in airplane mode.

As illustrated in <FIG> and <FIG>, propulsion systems 212a, 212b (including wing tips 214a, 214b), and wing segments 204a, 204b, which tilt relative to fuselage <NUM> between a first position (<FIG>), in which wing segments 204a, 204b, and propulsion systems 212a, 212b, are configured in a hover mode, and a second position (<FIG>), in which wing segments 204a, 204b, and propulsion systems 212a, 212b, are configured in a cruise mode.

The position of wing segments 204a, 204b, rotor assemblies of propulsion systems 212a, 212b, as well as the pitch of individual rotor blades of all of the propulsion systems 212a, 212b, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, propulsion systems 212a, 212b, are each convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Propulsion systems 212a, 212b, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Propulsion systems 212a, 212b, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 212a, 212b, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Propulsion systems 212a, 212b, may be tiltable between the vertical and horizontal positions by actuators that are tiltable in response to commands originating from a pilot and/or a flight control system. A linear actuator (or a group of two or more linear actuators for redundancy) attached to the aft spar as shown in <FIG> or a spindle connecting the two wing boxes as shown in <FIG> and pushing the trailing edge of the wing down are possible implementations.

<FIG> illustrate an example tiltrotor aircraft <NUM>, not in accordance with the appended claims, that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wing <NUM>, and tail assembly <NUM>. The aircraft further includes propulsion systems 312a, 312b. Propulsion systems 312a, 312b, are integrated into wing <NUM> proximate outboard ends thereof. Wing tips 314a, 314b, are fixedly connected to outboard sides of propulsion systems 312a, 312b.

Similar to the propulsion systems of aircraft <NUM>, each of propulsion systems 312a, 312b may include a drive system housing comprising a pylon, and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG>, the rotor assembly of each of propulsion systems 312a, 312b, includes three (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented. Rotation of rotor assemblies of propulsion systems 312a, 312b, generates lift while the aircraft <NUM> is operating in helicopter mode and thrust while the aircraft <NUM> is operating in airplane mode.

As illustrated in <FIG>, wing <NUM>, including propulsion systems 312a, 312b, and wing tips 314a, 314b, is tiltably connected to the fuselage <NUM>, and tilts relative to the fuselage between a first position (<FIG>), in which wing <NUM> and propulsion systems 312a, 312b, are configured in a hover mode, and a second position (<FIG>), in which wing <NUM> and propulsion systems 312a, 312b, are configured in a cruise mode.

The position of wing <NUM> and propulsion systems 312a, 312b, (including wing tips 314a, 314b) as well as the pitch of individual rotor blades of the propulsion systems 312a, 312b, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, wing <NUM>, including propulsion assemblies 312a, 312b, is convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Wing <NUM> and propulsion systems 312a, 312b, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Wing <NUM> and propulsion systems 312a, 312b, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 312a, 312b, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Wing <NUM> and propulsion systems 312a, 312b, may be tiltable between the vertical and horizontal positions by actuators (not shown) that are tiltable in response to commands originating from a pilot and/or a flight control system. <FIG> illustrate a possible actuator arrangement in which a linear actuator tilts the aft spar of the wing box down and forward up in a streamlined arrangement. Actuator attach points can be varied to tailor mechanical advantage.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM> that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wings 404a, 404b, booms 406a, 406b, connected to opposite sides of the fuselage <NUM>, and a tail assembly <NUM>. In accordance with features of embodiments described herein, aircraft further includes three pairs of propulsion systems, including a forward pair of boom-mounted propulsion systems 408a, 408b, an aft pair of boom-mounted propulsion systems 410a, 410b, and a pair of propulsion systems 412a, 412b. In the illustrated embodiment, propulsion systems 412a, 412b, are integrated into wings 404a, 404b, which are tiltably connected to outboard sides of booms 406a, 406b. Wing tips 414a, 414b, are fixedly connected to outboard sides of propulsion systems 412a, 412b. Propulsion systems 408a, 408b, are tiltably connected to the forward ends of wing booms 404a, 404b. Propulsion systems 410a, 410b, are mounted to top surfaces of booms 406a, 406b, proximate the aft end of the fuselage <NUM>.

Similar to the propulsion systems of aircraft <NUM>, each of propulsion systems 408a, 408b, 410a, 410b, 412a, and 412b may include a drive system housing comprising a pylon, and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, the rotor assembly of each of propulsion systems 408a, 408b, 412a, 412b, includes five (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented without departing from the scope of the embodiments described. It should also be recognized that rotor assemblies of propulsion systems 408a, 408b, may include a different number of rotor blades than rotor assemblies of propulsion systems 412a, 412b. Rotation of rotor assemblies of propulsion systems 408a, 408b, 412a, and 412b generates lift while the aircraft <NUM> is operating in helicopter mode and thrust while the aircraft <NUM> is operating in airplane mode.

In the illustrated embodiment, each boom-mounted propulsion system 410a, 410b, includes a drive system housing comprising a pylon and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, each rotor assembly of propulsion systems 410a, 410b, includes two (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented without departing from the scope of the embodiments described. Rotation of rotor assemblies of propulsion systems 410a, 410b, generates lift while the aircraft <NUM> is operating in helicopter mode. It will be recognized that while rotor assemblies of propulsion systems 410a, 410b, are illustrated as being disposed above (i.e., on top of) booms 406a, 406b, they may alternatively be disposed below (i.e., on the underside of) booms.

In accordance with features of embodiments described herein, and as illustrated in <FIG> and <FIG>, propulsion systems 412a, 412b, are integrated into wings 404a, 404b. Wings 404a, 404b, together with wing-mounted propulsion systems 412a, 412b (including wing extensions 414a, 414b), tilt relative to booms 406a, 406b, and fuselage <NUM> between a first position (<FIG>), in which wings 404a, 404b, and propulsion systems 412a, 412b, are configured in a hover mode, and a second position (<FIG>), in which wings 404a, 404b, and propulsion systems 412a, 412b, are configured in a cruise mode.

Forward propulsion systems 408a, 408b, are tiltably connected to forward ends of booms and tiltable between a first position (<FIG>), in which propulsion systems 408a, 408b, are configured in a hover mode, and a second position (<FIG>), in which propulsion systems 408a, 408b, are configured in a cruise mode. In accordance with features of embodiments described herein, aft propulsion systems 410a, 410b, are fixedly attached to booms 406a, 406b, aft of the wing <NUM> in hover mode and do not convert between hover mode (<FIG>) and cruise mode (<FIG>).

The position of wings 404a, 404b, including propulsion systems 412a, 412b, and propulsion systems 408a, 408b, as well as the pitch of individual rotor blades of all of the propulsion systems 408a, 408b, 410a, 410b, 412a, 412b, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, propulsion systems 408a, 408b, 412a, 412b, are each convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Propulsion systems 408a, 408b, 412a, 412b, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Propulsion systems 408a, 408b, 412a, 412b, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 408a, 408b, 412a, 412b, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Wings 404a, 404b, including propulsion systems 412a, 412b, and propulsion systems 408a, 408b, may be tiltable between the vertical and horizontal positions by actuators (not shown) that are tiltable in response to commands originating from a pilot and/or a flight control system. Linear actuators which attach to the wing via a spindle in the wing common to the wing ribs attach to a clevis on the side of the boom. The dual or triply- redundant electric or hydraulic actuator extends rotating the wing.

It should be noted that, although propulsion systems 408a, 408b, are shown and described as being tiltable between cruise and hover positions, those propulsion systems may be fixed in the hover positions, similarly to propulsion systems 410a, 410b.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM>, not in accordance with the appended claims, that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wings 504a, 504b, and a tail assembly <NUM>. In accordance with features of embodiments described herein, aircraft further includes a plurality of propulsion systems 508a-508f integrated into wings 504a, 504b.

Similar to the propulsion systems of aircraft <NUM>, each of propulsion systems 508a-508f may include a drive system housing comprising a pylon, and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, the rotor assembly of each of propulsion systems 508a-508f includes five (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented without departing from the scope of the embodiments described. It should also be recognized that rotor assemblies of propulsion systems 508a-508f may include different numbers of rotor blades. Still further, although six propulsion systems are illustrated, it will be recognized that more or fewer propulsion assemblies may be integrated into wings 504a, 504b. Rotation of one or more rotor assemblies of propulsion systems 508a-508f lift while the aircraft <NUM> is operating in helicopter mode and thrust while the aircraft <NUM> is operating in airplane mode.

As illustrated in <FIG> and <FIG>, wings 504a, 504b, including propulsion systems 508a-508f, are tiltably connected to the fuselage <NUM>, and tilt relative to the fuselage between a first position (FIG. <NUM> A), in which wings 504a, 504b, and propulsion systems 508a-508f, are configured in a hover mode, and a second position (<FIG>), in which wings 504a, 504b, and propulsion systems 508a-508f are configured in a cruise mode.

The position of wings 504a, 504b, and rotor assemblies of propulsion systems 508a-508f, as the pitch of individual rotor blades of all of the propulsion systems, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, wings 504a, 504b, including propulsion systems 508a-508f, are convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Wings 504a, 504b, including propulsion systems 508a-508f, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Wings 504a, 504b, including propulsion systems 508a-508f, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 508a-508f, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Wings 504a, 504b, and propulsion systems 508a-508f, may be tiltable between the vertical and horizontal positions by actuators (not shown) in response to commands originating from a pilot and/or a flight control system. Each wing or the complete wing may be actuated with a linear or rotary actuary. Examples of a possible mechanism are shown in <FIG> and <FIG>. In this case several motor driving several rotors/props are arranged along the rotating wing.

<FIG> illustrate in greater detail a mechanism for actuating a wing of a spindle wing configuration, such as illustrated in <FIG> and <FIG>. In particular, <FIG> show a linear actuator <NUM> actuating a spindle <NUM> connecting the left and right wing boxes 604a, 604b. Two or more linear actuators could also be used for redundancy. <FIG> shows the wings/wing boxes 604a, 604b, in horizontal mode. <FIG> shows the wings/wing boxes 604a, 604b in vertical mode. It will be noted that, although as shown in <FIG>, actuator <NUM> is a linear actuator, in various implementations, one or more rotary or other type of actuator may advantageously be employed.

<FIG> illustrate in greater detail a mechanism for actuating a wing of a carry-through wing configuration, such as illustrated in <FIG>. In <FIG>, a linear actuator <NUM> actuates a carry through torque box <NUM> of a continuous wing including left and right wing boxes 704a, 704b. Two or more linear actuators could also be used for redundancy. <FIG> shows the wings/wing boxes 704a, 704b, in horizontal mode. <FIG> shows the wings/wing boxes 704a, 704b in vertical mode. It will be noted that, although as shown in <FIG>, actuator <NUM> is a linear actuator, in various implementations, one or more rotary or other type of actuator may advantageously be employed.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM> that is convertible between a VTOL or hover (also commonly referred to as helicopter) mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and a cruise (also commonly referred to as airplane) mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wing <NUM>, and booms 806a, 806b, connected to the wing on opposite sides of the fuselage <NUM>. The aircraft further includes three pairs of propulsion systems, including a first pair of boom-mounted propulsion systems 808a, 808b, a second pair of boom-mounted propulsion systems 810a, 810b, and a pair of wing-mounted propulsion systems 812a, 812b. In the illustrated embodiment, propulsion systems 812a, 812b, are tiltably connected to the leading edge of wing <NUM> at outboard ends thereof, while propulsion systems 808a, 808b, are tiltably connected to the forward end of booms 806a, 806b inboard of propulsion systems 812a, 812b. Alternatively, propulsion systems 808a, 808b, may be tiltably connected to the forward edge of wing <NUM> inboard of propulsion systems 812a, 812b. Propulsion systems 810a, 810b, are mounted to bottom surfaces of booms 806a, 806b, proximate the aft end or aft of the fuselage <NUM>. Aircraft <NUM> further includes a tail assembly <NUM> at an aft end thereof.

Similar to the propulsion systems of aircraft <NUM>, each of propulsion systems 808a, 808b, 810a, 810b, 812a, and 812b may include a drive system housing comprising a pylon, and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, the rotor assembly of each of propulsion systems 808a, 808b, 812a, 812b, includes five (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented without departing from the scope of the embodiments described. It should also be recognized that rotor assemblies of propulsion systems 808a, 808b, may include a different number of rotor blades than rotor assemblies of propulsion systems 812a, 812b. Rotation of rotor assemblies of propulsion systems 808a, 808b, 812a, and 812b generates lift while the aircraft <NUM> is operating in helicopter mode and thrust while the aircraft <NUM> is operating in airplane mode.

In the illustrated embodiment, each boom-mounted propulsion system 810a, 810b, includes a drive system housing comprising a pylon and a rotatable open rotor assembly comprising a plurality of rotor blades connected to a rotor mast and configured to rotate about a rotor axis. As shown in <FIG> and <FIG>, each rotor assembly of propulsion systems 810a, 810b, includes two (<NUM>) rotor blades; however, it should be recognized that more or fewer blades may be implemented without departing from the scope of the embodiments described. Rotation of rotor assemblies of propulsion systems 810a, 810b, generates lift while the aircraft <NUM> is operating in helicopter mode. It will be recognized that while rotor assemblies of propulsion systems 810a, 810b, are illustrated as being disposed below (i.e., on the underside of) booms 806a, 806b, they may alternatively be disposed above (i.e., on top of) booms.

In accordance with features of embodiments described herein, and as illustrated in <FIG> and <FIG>, propulsion systems 808a, 808b, 812a, 812b, are tiltably connected to the wing <NUM> and tilt relative to wing between a first position (<FIG>), in which propulsion systems 808a, 808b, 812a, 812b, are configured in a hover mode, and a second position (<FIG>), in which propulsion systems 808a, 808b, 812a, 812b, are configured in a cruise mode. In accordance with features of embodiments described herein, aft propulsion systems 810a, 810b, are fixedly attached to booms 806a, 806b, aft of the wing <NUM> in hover mode and do not convert between hover mode (<FIG>) and cruise mode (<FIG>).

The position of rotor assemblies of propulsion systems 808a, 808b, 812a, 812b, as well as the pitch of individual rotor blades of all of the propulsion systems 808a, 808b, 810a, 810b, 812a, 812b, can be selectively controlled in order to selectively control direction, thrust, and lift of aircraft <NUM>. As previously noted, propulsion systems 808a, 808b, 812a, 812b, are each convertible, relative to fuselage <NUM>, between a vertical position, as shown in <FIG>, and a horizontal position, as shown in <FIG>. Propulsion systems 808a, 808b, 812a, 812b, are in the vertical position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of aircraft <NUM>. Propulsion systems 808a, 808b, 812a, 812b, are in the horizontal position during forward flight mode, in which aircraft <NUM> is in forward flight. In forward flight mode, propulsion systems 808a, 808b, 812a, 812b, direct their respective thrusts in the aft direction to propel aircraft <NUM> forward. Aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Propulsion systems 808a, 808b, 812a, 812b, may be tiltable between the vertical and horizontal positions by actuators (not shown) that are tiltable in response to commands originating from a pilot and/or a flight control system.

It should be noted that, although propulsion systems 808a, 808b, are shown and described as being tiltable between cruise and hover positions, those propulsion systems may be fixed in the hover positions, similarly to propulsion systems 810a, 810b.

In accordance with features of embodiments described herein, in certain embodiments, when aircraft <NUM> is in cruise mode, rotor assemblies of propulsion systems 810a, 810b, may cease rotation. In embodiments in which propulsion systems 808a, 808b, are also fixed (i.e., do not convert between hover and cruise modes), rotor assemblies thereof may also cease rotation when aircraft <NUM> is in cruise mode. For rotors fixed in a hover or horizontal position, stopping the rotor when in transition to cruise flight on the wing reduces power requirements not contributing to forward flight. Drag is reduced by stopping the rotor such that only the tip presents frontal area. Propulsive efficiency of the remaining rotors is increased as the remaining rotors blade loading increases in cruise in comparison to power lost as a function of rotating the blade.

<FIG> illustrates in greater detail connection of one of forward propulsion systems of aircraft <NUM> (e.g., propulsion system 808a) to forward end of one of booms of aircraft <NUM> (e.g., boom 806a). In <FIG>, pylon 806a includes two clevises 840a, 840b, that engage opposite sides of a pylon support spindle <NUM> in a manner that enables on a bearing surface between horizontal and vertical (as shown in <FIG>.

<FIG> illustrates a pylon configuration in which a rotor pylon <NUM> and rotation axis <NUM> are elevated above the wing torque box <NUM>. A pylon support spindle <NUM> is engaged on opposite sides thereof by bearing surface of clevises 908a, 908b. A linear actuator (not shown in <FIG>) attached to a spindle (not shown in <FIG>) in the wing torque box <NUM> and to the pylon support <NUM> actuates the pylon <NUM> between horizontal (as shown in <FIG>) and vertical orientations.

<FIG> illustrates a drive system <NUM> that may be deployed in any of the propulsion systems described hereinabove. As shown in <FIG> drive system <NUM> includes multiple electric motors <NUM> for providing rotational energy to a rotor assembly <NUM> via a gearbox <NUM>.

<FIG> illustrates a drive system <NUM> that may be deployed in any of the propulsion systems described hereinabove. As shown in <FIG>, drive system <NUM> includes a single electrical motor for providing rotational energy to a rotor assembly <NUM>.

The drive system (such as drive system <NUM> or <NUM>) for a rotor assembly may tilt with the rotor assembly (e.g., located in a rotating pylon or in a rotating portion of a pylon) or may be fixed (i.e., non-tilting). In embodiments in which the drive system is fixed, the drive system may be located in a fixed portion of a partially tilting pylon, in which case a gearbox is used to allow transmittal across the rotation, or in the fuselage with a driveshaft down the wing. There may be a drive assembly in the pylon and a drive shaft and a group of motors disposed within the fuselage to allow redundancy with a reduced number of motors.

The electric tiltrotor configurations described herein are characterized by tilting of the rotors on a wing. The tiltrotor configurations described herein rotate the rotor pylon at the side pylon of body, at a wing station inboard on the wing, or by incorporating tiltwing elements with wing rotation as a whole. The degree of wing rotation with the pylon and placement of the axis of rotation relative to the wing may be customized depending on the embodiment. Additionally, the number of motors and the manner in which the motors are arranged in a rotating or fixed pylon or inboard in the fuselage with a drive shaft extending through the wing to the rotor assembly may also be customized depending on the embodiment. Pylon rotation may be actuated using one or more linear and/or rotary actuators located forward of, behind, or beneath the pylon depending on the embodiment.

Various tilting rotor pylon embodiments include embodiments in which the entire pylon and outboard of the pylon rotates, the entire pylon (and outboard) and a portion of the inboard wing structure rotates, the entire pylon and the entire wing structure rotates (i.e., tiltwing), and a portion of the pylon rotates either in line with the pylon or above the wing structure. Additionally, the electric motor or motors may be located in the rotating pylon, in a rotating portion of the pylon or a fixed portion of the pylon with a gearbox to allow transmittal across the rotation, and/or in the fuselage with a drive shaft down the wing and appropriate gearboxes for driving the rotor assembly. Additionally, one or more motors could be located in the pylon and one or more motors could also be located in the fuselage with a down-wing drive shaft to allow redundancy with a reduced number of motors.

Embodiments described herein support both flapping rotor and rigid rotor/prop pylon rotation. The pylon rotates about an axis within the wing or above the wing. In various embodiments, none of the wing structure, a portion of the wing structure, or all of the wing structure may rotate with the pylon. One or more motors for driving a combining gearbox to drive rotors may be arrayed in the rotor pylon or in the fuselage with or without an interconnect between rotors. Linear or rotary actuators may be used to implement pylon rotation.

Tilting portions offer a tradeoff between stalled wing in transition and a download in hover. Rotating the wing or a portion of the wing with the pylon increases the area of the wing seeing a high angle of attack and encountering stall versus additional download of a non-rotated wing in hover. A wing extension beyond the pylon increase cruise performance.

It should be appreciated that aircraft illustrated herein, such as aircraft <NUM>, is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. The components of rotor assemblies described herein may comprise any materials suitable for use with an aircraft rotor. For example, rotor blades and other components may comprise carbon fiber, fiberglass, or aluminum; and rotor masts and other components may comprise steel or titanium.

Claim 1:
An aircraft (<NUM>, <NUM>) comprising:
a fuselage (<NUM>, <NUM>) ;
a wing (404a, 404b, <NUM>) connected to the fuselage (<NUM>, <NUM>)
first and second propulsion systems (408a, 408b, 412a, 412b, 808a, 808b, 812a, 812b) connected to the wing on opposite sides of the fuselage (<NUM>, <NUM>), wherein at least a portion of each of the first and second propulsion systems (408a, 408b, 412a, 412b, 808a, 808b, 812a, 812b) are tiltable between a first position in which the aircraft (<NUM>, <NUM>) is in a hover mode and a second position in which the aircraft is in a cruise mode;
a pair of booms (406a, 406b, 806a, 806b) that are connected to opposite sides of the fuselage (<NUM>, <NUM>); and
an aft pair of boom-mounted propulsion systems (410a, 410b, 810a, 810b), wherein the aft pair of boom-mounted propulsion systems (410a, 410b, 810a, 810b) are fixedly attached to the pair of booms (406a, 406b, 806a, 806b);
wherein the wing (404a, 404b, <NUM>) comprises wing tips (414a, 414b) disposed outboard of the first and second propulsion systems (408a, 408b, 412a, 412b, 808a, 808b, 812a, 812b); and
wherein each of the first and second propulsion systems (408a, 408b, 412a, 412b, 808a, 808b, 812a, 812b) is an open rotor assembly including a pylon and a rotor assembly comprising a plurality of rotor blades.