Large vertical takeoff and landing aircraft

Abstract

Disclosed is an aircraft comprising: a fuselage (1); a forward lifting wing (2) with a first wingspan; an aft lifting wing (4) with a second wingspan, where the second wingspan is larger than the first wingspan; a first and second proprotor (3) mounted at each wing tip of the forward lifting wing; a third and fourth proprotor (3) mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor (5) mounted on the aft lifting wing between the fuselage and each of the third and fourth proprotors.

Description

[0001] LARGE VERTICAL TAKEOFF AND LANDING AIRCRAFT

[0002] Technical Field

[0003] The present disclosure relates to the field of vertical take-off and landing (VTOL) aircraft.

[0004] Technical Background

[0005] Large urban areas are often difficult to navigate due to severe road congestion and inadequate ground-based public transport. The majority of trips required in this environment are less than 50 kilometres, and modern batteries have enabled electric aircraft that can fly this distance and more. Vertical take-off and landing (VTOL) allows for passenger transport within congested urban areas without the need for long runways. Combining electric propulsion with VTOL has enabled a new class of so-called eVTOL aircraft. Significant entrants into this class of aircraft include Volocopter, Joby, Archer, Supernal, Autoflight, and Vertical Aerospace, among others.

[0006] The concept of urban air mobility relies on eVTOLs performing these missions commercially. All the above existing eVTOL aircraft are designed for 1-6 passengers, which can lead to relatively high operating costs per passenger-mile, similar to private aircraft or helicopters today. It is anticipated that a large proportion of proposed eVTOL aircraft journeys will be from a limited number of vertiports, for example from downtown to the airport, and a much larger aircraft may enable significant cost reduction by carrying more passengers at a time, similar to the cost advantages of a bus over private cars. Furthermore, there are significant reductions in airspace congestion, and frequency of operation - which can be less obtrusive in a crowded urban area. At the same time the energy usage and subsequent environmental impact per passenger may be reduced.

[0007] The current state of the art in the engineering technical design of such aircraft has experienced challenges and problems, including how to make a large eVTOL aircraft provide enough lift, efficiently, in helicopter mode (where the aircraft is moving vertically) to lift 20- 50 passengers while also being compact enough to utilize existing ground infrastructure. In addition, it is preferable that the weight and acquisition costs be minimized, along with operating costs. To this end overall complexity and aerodynamic drag should be minimized and the aerodynamic interference of combination lift / propulsion units should be well managed.

[0008] Summary

[0009] Disclosed is an aircraft as claimed in claim 1. Optional but preferred technical features are recited in the dependent claims. Also provided is a method of operating an aircraft, as claimed in claim 10.

[0010] In a first aspect, there is provided an aircraft comprising: a fuselage; a forward lifting wing with a first wingspan; an aft lifting wing with a second wingspan, where the second wingspan is larger than the first wingspan, wherein the aft lifting wing has an aft lifting wing leading edge; a first and second proprotor mounted at each wing tip of the forward lifting wing; a third and fourth proprotor mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor mounted on the aft lifting wing leading edge between the fuselage and each of the third and fourth proprotors.

[0011] This configuration may provide sufficient lift for moving large passenger numbers in a mechanically simple and compact configuration. Additionally or alternatively, this configuration may provide sufficient stability and redundancy to avoid the need for complex mechanical linkages between proprotors because e.g. if power is lost to any one proprotor then the other five proprotors can be used to land safely. This in turn simplifies mechanical design, reduces costs and weight. This is in contrast to some prior art designs where a complex mechanical linkage is required to ensure that when an engine fails on one side of the fuselage the engine associated the proprotor on the opposite side of the fuselage can drive both proprotors.

[0012] It may be that the total number of lifting wings is two. Thus, it may be that the aircraft comprises only two lifting wings. It may be that the aircraft does not include an empennage (tail assembly). Typically, an empennage comprises vertical and horizontal surfaces for stabilizing yaw and pitch.

[0013] It may be that the total number of proprotors is six. Thus, it may be that the aircraft comprises only six proprotors.

[0014] It will be appreciated that, in the present disclosure, a "wing" extends from a first outboard wingtip to a second outboard wingtip. Thus, a wing extends to both sides of the fuselage.

[0015] It will be appreciated that each wing is a fixed wing, e.g. the position of each wing is fixed relative to the fuselage.

[0016] The term "proprotor" will be known to the skilled person and denotes a combination propeller / rotor. That is to say, a unit with a plurality of spinning aerofoils ("blades") that functions as both a propeller (e.g. as found on an airplane) and a rotor (e.g. as found on a helicopter). The aircraft may comprise an (electric) motor associated with each proprotor (i.e. each proprotor has its own dedicated motor). The aircraft may comprise an (electric) drive associated with each proprotor. The aircraft may comprise a control system configured to control the operation of each proprotor. Thus, it may be that each proprotor has an electric motor(s) that drives the proprotor directly or via a gearbox. It may be that the proprotors / their motors are arranged to be driven from a battery supply. Thus the aircraft may comprise one or more batteries configured to power the proprotors. The aircraft may comprise a control system configured to operate the proprotors (for example to tilt the proprotors, adjust blade pitch and / or adjust the RPM of the proprotors) in response to a user input.

[0017] It may be that at least two, for example each, of the proprotors tilt (i.e. are tiltability attached to the wing). Thus, the or each proprotor may be attached to the wing such that the angle of attack of the axis of rotation of the blades is moveable relative to the wing. For example, the or each proprotor may be attached for movement between a first configuration (a helicopter mode) in which the axis of rotation of the blades is substantially perpendicular to the longitudinal axis of the aircraft (i.e. vertical) and a second configuration (an airplane mode) in which the axis of rotation of the blades is substantially parallel with the longitudinal axis of the aircraft (i.e. horizontal). It may be that at least two, for example each, of the proprotors tilt by 90 degrees.

[0018] As used herein the term "substantially" perpendicular or parallel to the longitudinal axis of the aircraft denotes within + / - 10 degrees of the longitudinal axis of the aircraft.

[0019] It may be the aircraft is a tiltrotor aircraft. Thus, each proprotor may comprise a rotor hub to which the blades are mounted, and the aircraft is configured such that the angle of attack of the rotor hub relative to the wing is changed to move the aircraft between airplane mode and helicopter mode.

[0020] It may be that at least two, for example each, of the proprotors are configured to adjust collective blade pitch or RPM or both to control the proprotor thrust and thus the aircraft attitude. It may be that at least two, for example each, of the proprotors have variable cyclic blade pitch.

[0021] It may be that the aircraft, for example each proprotor, is electrically-powered.

[0022] It may be that the aircraft comprises control surfaces on each of the forward lifting wing and the aft lifting wing. Each control surface may be mounted for movement, e.g. hinged, relative to the rest of the wing.

[0023] It may be that each of the first, second, third, fourth, fifth, and sixth proprotors has a plurality of blades.

[0024] It may be that each of the first, second, third, fourth, fifth, and sixth proprotors has an electric motor.

[0025] It may be that each of the proprotors is configured to operate independently of any other proprotor. For example, it may be that there is no mechanical linkage connecting one of said proprotors to another of said proprotors such that power can be transferred between said proprotors.

[0026] It may be that the aircraft is a passenger aircraft, for example a 20 - 50 passenger aircraft. It may be that the fuselage accommodates between 20 and 50 passengers plus crew. For example, the fuselage may be sized to accommodate 30 people. It may be that the aircraft comprises internal hand baggage space. It may be that the aircraft comprises an externally- accessible baggage compartment for larger luggage.

[0027] It may be that the forward lifting wing (the forward wing) and / or aft lifting wing (the aft wing) is mounted on the top of the fuselage. It may be that the forward wing and aft wing are mounted at the same vertical position (i.e. vertical distance from horizontal ground when the landing gear is deployed). It may be that the vertical position of the forward and aft wings differs by less than or equal to 0.5m.

[0028] It will be appreciated that the forward wing is located in the front half of the aircraft. It will be appreciated that the aft wing is located in the rear half of the aircraft. The aircraft may have a mid-body position being located halfway between the foremost and aftmost points of the fuselage. The forward wing may be forward of the mid-body position. The aft wing may be aft of the mid-body position.

[0029] It may be that the first and second proprotors are outboard of the fifth and sixth proprotors.

[0030] It may be that the wingspan of the aft wing is up to twice the wingspan of the forward wing. It may be that the wingspan of the aft wing is from 15m to 20m inclusive; and the wingspan of the forward wing is from 8m to 12m inclusive. It will be appreciated that the wingspan will depend on the size of the aircraft (i.e. upon the number of passengers that can be accommodated). In the case that the aircraft can seat 30 people, it may be that the aft wing has a wingspan of 17.5m, and the forward wing has a wingspan of 10 m.

[0031] A proprotor has a diameter and number of blades that will vary with the exact size of the aircraft. It may be that the diameter (i.e. radius of the blades multiplied by two) is from 4m to 6m inclusive. In the case the aircraft can seat 30 people, it may be that each proprotor has a diameter of 4.5m and has between 5 and 7 blades.

[0032] In a second aspect, there is disclosed a method of operating an aircraft which comprises a fuselage; a forward lifting wing (forward wing) with a first wingspan; an aft lifting wing (aft wing) with a second wingspan, where the second wingspan is larger than the first wingspan, wherein the aft lifting wing has an aft lifting wing leading edge; a first and second proprotor mounted at each wing tip of the forward lifting wing; a third and fourth proprotor mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor mounted on the aft lifting wing leading edge between the fuselage and each of the third and fourth proprotors. The method comprises the steps of:

[0033] It may be that the aircraft takes off vertically with at least two, for example all, of the proprotors in a first configuration (helicopter mode) in which the axis of rotation of the blades is substantially perpendicular to the longitudinal axis of the aircraft (e.g. each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings). And then, it may be that said at least two, for example all, of the proprotors are tilted from the first configuration to a second configuration (airplane mode) in which the axis of rotation of the blades is substantially parallel with the longitudinal axis of the aircraft (e.g. each of the proprotors is rotated so that it is oriented in a direction which is parallel to the direction of flight and to the top surface of the forward and aft lifting wings) for forward flight.

[0034] Additionally or alternatively, it may be that that in forward flight at least two, for example all, of the proprotors are in a second configuration (airplane mode) in which the axis of rotation of the blades is substantially parallel with the longitudinal axis of the aircraft (e.g. each of the proprotors is rotated so that it is oriented in a direction which is parallel to the direction of flight and to the top surface of the forward and aft lifting wings for forward flight). And then, it may be that said at least two, for example all, of the proprotors are tilted from the second configuration to the first configuration (helicopter mode) in which the axis of rotation of the blades is substantially perpendicular to the longitudinal axis of the aircraft (e.g. each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings) and the aircraft lands vertically.

[0035] The method may comprise:

[0036] (a) each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings;

[0037] (b) the aircraft takes off vertically;

[0038] (c) each of the proprotors is rotated so that it is oriented in a direction which is parallel to the direction of flight and to the top surface of the forward and aft lifting wings for forward flight;

[0039] (d) each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings; and

[0040] (e) the aircraft lands vertically.

[0041] It may be that said at least two or each proprotor is tilted by 90 degrees when moving between the first and second configurations.

[0042] The method may comprise for at least two, for example for each, proprotor adjusting collective blade pitch or RPM or both to control the proprotor thrust and thus the aircraft attitude.

[0043] It will of course be appreciated that features described in relation to one aspect of the disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the disclosure may incorporate any of the features described with reference to the apparatus of the disclosure and vice versa.

[0044] Brief Description of the Drawings

[0045] Figure 1 shows an isometric view of the aircraft in helicopter mode, according to an example embodiment; Figure 2 shows a plan view of the aircraft in airplane mode, with the forward and aft wings and the wingtip and inboard propulsion units horizontal in order to provide forward thrust, according to an example embodiment;

[0046] Figure 3 shows a left profile view of the aircraft in airplane mode, according to an example embodiment;

[0047] Figure 4 shows a front view of the aircraft in airplane mode, according to an example embodiment;

[0048] Figure 5 shows a plan view of the aircraft in helicopter mode, with the landing gear extended. The tip propulsion units are tilted up roughly 90 degrees, and the forward sections of the inboard propulsion units are also tilted, in order to provide vertical lift, according to an example embodiment;

[0049] Figure 6 shows a left profile view of the aircraft in helicopter mode, according to an example embodiment;

[0050] Figure 7 shows a front view of the aircraft in helicopter mode, according to an example embodiment;

[0051] Figure 8a is a flowchart showing an operation of the aircraft, according to an example embodiment; and

[0052] Figure 8b is a diagram showing the aircraft at each step of the flowchart of Fig. 8a.

[0053] Detailed Description of Example Embodiments

[0054] The example embodiment relates to a large eVTOL aircraft as shown in Figs. 1 and 2.

[0055] This aircraft in Figs. 1 and 2 preferably includes a fuselage 1 (see Fig. 2) which accommodates between 20 to 50 passengers, supported on two lifting wings - a smaller forward wing 2 (Fig. 2) with a tilting propulsion unit 3 at each wing tip, and a larger aft wing 4 with similar wingtip propulsion units 3 and two additional propulsion units 5 mounted on the leading edge 9 (Fig. 2) of the aft wing 4, between the fuselage and the wing tip. Each propulsion unit 3 comprises a combination propeller / rotor (proprotor) with its electric motor and associated drive and control systems.

[0056] The aircraft is shown in helicopter mode in Fig. 1, with the wingtip propulsion units 3 tilted up and the forward section of the inboard propulsion units 5 tilted up. In this configuration the aircraft will take-off and climb until clear of the ground infrastructure, at which point it will tilt some or all of the propulsion units down approximately 90 degrees to provide forward thrust and continue to climb to its cruise altitude (which is referred to here as the aircraft being in airplane mode). Upon approach to its destination, it will slow and descend and will tilt the proprotors back up into helicopter mode for its final approach and landing.

[0057] The aircraft according to an example embodiment is shown in airplane mode in Fig. 2, which shows a fuselage 1 that accommodates between 20 and 50 passengers plus crew. It has internal hand baggage space and an externally-accessible baggage compartment for larger luggage. The forward wing 2 is mounted on the top of the fuselage and supports a propulsion unit 3 at each wing tip. The aft wing 4 has a greater wingspan and supports a propulsion unit 3 at each wing tip, and in addition has two inboard propulsion units 5 mounted on the wing leading edges between the fuselage and the tip-mounted units. As shown in Fig. 1, the aft wing 4 is preferably up to twice as large in wingspan as compared to the forward wing 2. For example, in an embodiment, where the aircraft can seat 30 people, the aft wing 4 has a span of 17.5m from wing tip to wing tip, whereas the forward wing 2 has a span of 10.0m. A range for these lengths can be between 15m and 20m for the aft wing 4 and between 8m and 12m for the forward wing 2, depending upon the number of passengers.

[0058] Each propulsion unit comprises a proprotor which has a diameter and number of blades that will vary with the exact size of the aircraft. For example, in an embodiment, where the aircraft can seat 30 people, each proprotor has a diameter of 4.5m and has between 5 and 7 blades. A range for the diameter can be between 4m and 6m. Each proprotor has an electric motor(s) that may drive the proprotor directly or via a gearbox, and also has the electronics required to drive the motors from a battery supply.

[0059] The nominal lateral extent of the proprotors is illustrated by the dashed lines 6 in Fig. 4.

[0060] The wing taper ratio, dihedral, and leading-edge sweep angles are subject to variation as deemed appropriate for specific sizing and applications. For example, in an embodiment where the aircraft is designed to seat 30 people, the proposed values for these are: taper ratio: forward wing 2 - 0.55, aft wing 4 - 0.4; both wings' dihedral - 0 degrees; both wings' leading-edge sweep - 0 degrees. For example, ranges for each of these are as follows: taper ratio; forward wing 2 - between 0.4 and 0.6, aft wing 4 - between 0.35 and 0.55: both wings' dihedral; between -2 and +3 degrees; both wings' leading-edge sweep - between -5 and +5 degrees.

[0061] The control surfaces on the wing trailing edges 7 (in Fig. 2) are shown in their airplane mode position.

[0062] The locations of the wings 2 and 4 on top of the fuselage 1 are shown in profile in Figure 3, and in Figure 4 the relationship between the fuselage 1 and the wings 2 and 4 is most clear. The extent of each proprotor is indicated by the dashed circles 6. Note that the exact height of each wing above the fuselage may not be the same as the aerodynamic interference impact is established. For example, in an embodiment, the heights of the wings 2 & 4 may be the same. Ranges for these values may be up to 0.5m different.

[0063] The relationship between the 6 proprotors and the wings 2 and 4 and fuselage 1 is shown in Figure 5 and the propulsion units 3 and 5 are shown in the helicopter mode. Note that the relationship between the wings and rotors will be optimized to minimize the rotor downwash impact on the wings and thus optimize lift. Specifically note that the control surfaces 7 shown in Figure 2 are not visible in Figure 5 as they are folded down out of the way of the proprotor downwash. The profile view of the aircraft in helicopter mode is shown in Fig. 6, illustrating how the 4 wingtip propulsion units 3 rotate in entirety while only the forward section of the inboard units 5 tilts. This view also illustrates a notional landing gear configuration 8.

[0064] As shown in Fig. 7, the front view of the aircraft in helicopter mode, shows the propulsion units 3 and 5 tilted up to provide lift and control in hover. The amount of inboard / outboard tilt will be optimized to minimize interference between rotors but will be in the region of 2 - 5 degrees.

[0065] Fig. 8a is a flowchart that shows the steps of a method of operating the described aircraft.

[0066] A first step 81, pre-takeoff, at least two of the proprotors, preferably all 6 of the proprotors, are rotated so that their axes are oriented at, or approximately at, 90 degrees to the ground. In this position, the aircraft is in helicopter mode, where it will be loading passengers and baggage, and charging the batteries as required.

[0067] At a second step 82, takeoff, where the aircraft is performing vertical take-off, the landing gear is retracted and the aircraft climbs vertically to a safe altitude.

[0068] At a third step 83, cruise, at least two of the proprotors, preferably all 6 of the proprotors, are rotated so that they are oriented in a direction which is parallel or approximately parallel, to the direction of flight while the aircraft accelerates to cruise speed. In this position, the aircraft is in airplane mode, where the aircraft has reached its cruising altitude and moves horizontally to its destination.

[0069] At a fourth step 84, approach & landing, at least two of the proprotors, preferably all 6 of the proprotors, are rotated so that they are oriented at, or approximately at, 90 degrees to the ground in helicopter mode, while the aircraft decelerates to enter a hover and extend the landing gear. At a fifth step 85, post landing, the aircraft has performed a vertical landing at the aircraft's destination. The aircraft taxis to the terminal to unload passengers and baggage and the batteries are plugged in to charge, if appropriate.

[0070] Fig. 8b shows the aircraft at each step 81, 82, 83, 84, and 85 of the method, according to the flowchart of Fig. 8a.

[0071] Accordingly, the present disclosure proposes a unique configuration for a VTOL aircraft, which is preferably an eVTOL, which addresses at least some of the above-described technical engineering challenges, as well as others. This configuration preferably features wings and proprotors sized for efficiency while minimizing download from the proprotor downwash onto the wings and retaining a compact footprint allowing it to access many verti ports.

[0072] Control in airplane mode is provided by one or more hinged control surfaces 7 on each wing. In helicopter mode control is provided by one or more rotors having variable blade cyclic and / or collective pitch and variable RPM (revolutions per minute). The hinged control surfaces 7 may be displaced downward approximately 90 degrees under the rotors to minimize the download from the tip rotors' downwash.

[0073] Although a battery-electrically powered aircraft is described above, the aircraft could also be powered by other means, such as standard fuels or hydrogen fuel cell.

[0074] In embodiments, the aircraft disclosed relates to a 20-50 passenger battery-electric aircraft capable of vertical take-off and landing.

Claims

Claims:

1. An aircraft comprising: a fuselage; a forward lifting wing with a first wingspan; an aft lifting wing with a second wingspan, where the second wingspan is larger than the first wingspan, wherein the aft lifting wing has an aft lifting wing leading edge; a first and second proprotor mounted at each wing tip of the forward lifting wing; a third and fourth proprotor mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor mounted on the aft lifting wing leading edge between the fuselage and each of the third and fourth proprotors.

2. The aircraft according to claim 1, the aircraft having a total of two lifting wings, being the forward lifting wing and the aft lifting wing.

3. The aircraft according to claim 1 or claim 2, the aircraft having a total of six proprotors, being the first, second, third, fourth, fifth and sixth proprotors.

4. The aircraft according to any previous claim, wherein the forward and aft lifting wings are fixed wings.

5. The aircraft according to any previous claim, wherein the aircraft is a passenger aircraft, for example a 20 - 50 passenger aircraft.

6. The aircraft according to any previous claim, wherein the aircraft is a tiltrotor aircraft, for example a tiltrotor vertical take-off and landing (VTOL) aircraft.

7. The aircraft according to any previous claim wherein at least two, for example each, of the proprotors tilt.

8. The aircraft according to claim 7 wherein at least two, for example each, of the proprotors tilt by 90 degrees.

9. The aircraft according to any previous claim, where at least two of the proprotors adjust collective blade pitch or RPM or both to control the proprotor thrust and thus the aircraft attitude.

10. The aircraft according to any previous claim, wherein at least two of the proprotors have variable cyclic blade pitch.

11. The aircraft according to any previous claim, wherein the aircraft is electrically-powered.

12. The aircraft according to any previous claim, further comprising moveable, for example hinged, control surfaces on each of the forward lifting wing and the aft lifting wing.

13. The aircraft according to any previous claim, wherein each of the first, second, third, fourth, fifth, and sixth proprotors has a plurality of blades.

14. The aircraft according to any previous claim, wherein each of the first, second, third, fourth, fifth, and sixth proprotors has an electric motor.

15. A method of operating an aircraft which comprises a fuselage; a forward lifting wing with a first wingspan; an aft lifting wing with a second wingspan, where the second wingspan is larger than the first wingspan, wherein the aft lifting wing has an aft lifting wing leading edge; a first and second proprotor mounted at each wing tip of the forward lifting wing; a third and fourth proprotor mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor mounted on the aft lifting wing leading edge between the fuselage and each of the third and fourth proprotors; the method comprising:(i) the aircraft takes off vertically with at least two, for example all, of the proprotors in a first configuration (helicopter mode) in which the axis of rotation of the blades is substantially perpendicular to the longitudinal axis of the aircraft; and then(ii) said proprotors are tilted from the first configuration to a second configuration (airplane mode) in which the axis of rotation of the blades is substantially parallel with the longitudinal axis of the aircraft for forward flight; and / or the method comprising:(i) in forward flight at least two, for example all, of the proprotors are in a second configuration (airplane mode) in which the axis of rotation of the blades is substantially parallel with the longitudinal axis of the aircraft; and then(ii) said proprotors are tilted from the second configuration to the first configuration (helicopter mode) in which the axis of rotation of the blades is substantially perpendicular to the longitudinal axis of the aircraft and the aircraft lands vertically.

16. A method of operating an aircraft which comprises a fuselage; a forward lifting wing with a first wingspan; an aft lifting wing with a second wingspan, where the second wingspan is larger than the first wingspan, wherein the aft lifting wing has an aft lifting wing leading edge; a first and second proprotor mounted at each wing tip of the forward lifting wing; a third and fourth proprotor mounted at each wing tip of the aft lifting wing; and a fifth and sixth proprotor mounted on the aft lifting wing leading edge between the fuselage and each of the third and fourth proprotors; the method comprising:(a) each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings;(b) the aircraft takes off vertically;(c) each of the proprotors is rotated so that it is oriented in a direction which is parallel to the direction of flight and to the top surface of the forward and aft lifting wings for forward flight;(d) each of the proprotors is rotated so that it is oriented at 90 degrees to the top surface of the forward and aft lifting wings; and(e) the aircraft lands vertically.

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