Vertical takeoff and landing aircraft

Abstract

A vertical take-off and landing aircraft (1) comprises a fuselage (2), at least one propulsion system (5), at least four lift propellers (10), and at least two fixed wing planes (20, 30, 40), the fixed wing planes (30, 40) located rearward of the forwardmost lift propellers (10) being located above the lift propellers (10). The lift propellers (10) are distributed on either side of the fixed wing planes (30) and on either side of the fuselage (2) such that the lift propellers (10) are separated in the longitudinal direction by at least the size of the chord (Cl, C2) of the fixed wing planes located between the lift propellers (10) and in the lateral direction by at least the width (L1, L2) of the fuselage (2) located between the lift propellers (10). At least one of the fixed wing planes (30) has a variable wingspan and the aircraft (1) comprises a control system for varying the wingspan in flight.

Description

Technical Field

[0001] This invention relates to vertical takeoff and landing (VTOL) aircraft, or "VTOL" aircraft. More specifically, this invention relates to variable-span VTOL aircraft. Background Technology

[0002] Various VTOL aircraft configurations have been studied in the past, typically with the aim of avoiding a degradation of the aircraft's inherent aerodynamic performance. In fact, such devices usually feature multiple propellers in addition to a fixed wing plane for takeoff during forward flight, ensuring lift during takeoff and vertical landing. Furthermore, if the propellers are designed to pivot, they can provide propulsion, or propulsion can be provided by other devices such as fans, turbojet engines, or any other thrust-generating mechanism.

[0003] Using both fixed-wing planes and propellers on the same VTOL aircraft inevitably leads to aerodynamic interactions between the wakes of these components (propeller / fixed-wing plane wake, propeller / propeller wake, fixed-wing plane / fixed-wing plane wake). These interactions typically affect the aerodynamic performance of the aircraft, thereby impacting its flight characteristics and mission performance.

[0004] This phenomenon is exacerbated when aircraft are equipped with electric motor propellers. In fact, to achieve the same takeoff power compared to other types of electric motors or engines, a greater number of electric motors is needed, which in turn increases the number of propellers for lift. Furthermore, flight safety requirements often lead to an increase in the number of propellers to compensate for electric motor failures. This increased number of propellers intensifies the interaction phenomena and their impact on aircraft performance. Moreover, so many propellers necessitate modifications to the fixed-wing plane for takeoff and landing, ultimately resulting in a relatively large length and width for the aircraft. This lack of compactness means that the aircraft cannot take off or land in restricted areas such as forests (open spaces, wooded areas) or urban areas.

[0005] Finally, limiting the weight of VTOL aircraft is an ongoing concern.

[0006] Therefore, a new type of VTOL aircraft is needed, which is more compact, relatively lighter, and has reduced aerodynamic interactions. Summary of the Invention

[0007] The vertical takeoff and landing aircraft according to the present invention includes a fuselage, at least one propulsion system, four lift propellers, and at least two fixed wing planes, the fixed wing planes including a main wing plane and a rear wing plane located at the rear of the aircraft. Both the main wing plane and the rear wing plane are located behind and above the foremost lift propeller. The main wing plane has a variable wingspan and includes a pair of wings, each wing being foldable along the lateral axis of the aircraft such that a movable end portion of the wing is positioned along and above a fixed portion of the wing when folded. The aircraft includes a control system for changing the wingspan of the main wing plane in flight by laterally deploying each wing. The four lift propellers are distributed on both sides of the main wing plane and on both sides of the fuselage, such that:

[0008] Two lifting propellers located on the same side of the fuselage are connected to a fixed portion of the wing on that side of the fuselage and are longitudinally spaced at least by the chord length between the two lifting propellers on that side of the fuselage at the fixed wing plane, and the two lifting propellers located on the same side of the main plane are transversely spaced at least by the width between the two lifting propellers on that side of the fuselage at the main plane.

[0009] This aircraft incorporates structures designed to reduce the aerodynamic interactions between the lifting propellers and the fixed wing plane. Specifically, the relative positions of the fixed wing plane and the lifting propellers are configured such that the wakes of all propellers have negligible aerodynamic effects on the fixed wing plane located downstream of these propellers. Similarly, folding the movable end portions of each wing over the fixed portions of the wing reduces the aerodynamic interactions with the propellers during folding.

[0010] In addition, the variable wingspan of the main plane reduces the overall lateral dimension of the wing plane, thus making the aircraft more compact during vertical takeoff and landing.

[0011] Finally, the fixed portion of each wing functions to support the mechanical stresses associated with the folding wing, but also to withstand the mechanical stresses associated with the two lift propellers attached to the wing. Therefore, the fixed portion can be designed to provide the mechanical strength required for this dual function. In contrast, other parts of the aircraft that eliminate these mechanical stresses can be designed with greater freedom. In particular, the overall size and mass of the fuselage can be limited while preserving accessible internal space. Ultimately, concentrating the mechanical stresses in the fixed portion of the wing results in a more compact and optimized mass structure compared to distributing these stresses among different parts of the aircraft.

[0012] Furthermore, the positioning of the lift propeller relative to the fixed wing plane reduces the aerodynamic load impact of the propeller wake on the fixed wing plane, especially the main wing plane. Therefore, the propeller does not add additional mechanical stress to the fixed portion of the wing plane.

[0013] In some implementations, the control system is configured to increase the wingspan when transitioning from low-speed flight to cruise flight and to decrease the wingspan when transitioning from cruise flight to low-speed flight. Therefore, the wingspan during cruise flight is greater than that during low-speed flight. Specifically, the wingspan is greatest during cruise flight and least during low-speed flight.

[0014] A fixed wing refers to all the non-rotating lifting surfaces of an aircraft. The wing section is the so-called "fixed" wing section, as opposed to the so-called "rotor" wing section. Certain parts of a fixed wing section can still move, thus changing the wingspan. The fixed wing plane can be a pair of wing sections (the pairs of wing sections can join above or at the bottom of the fuselage, or can extend to the sides of the fuselage), a tail section, or a canard section of lifting surfaces.

[0015] In this specification, the longitudinal and lateral directions are parallel to the longitudinal and lateral axes of the aircraft, respectively. The aircraft's axis is an imaginary line, which passes through the aircraft in the following manner:

[0016] - The longitudinal axis or roll axis extends from the nose (front end) of the aircraft to the tail (rear end), passes through the fuselage and through the center of gravity of the equipment;

[0017] - The lateral or pitch axis extends from one end of the main fixed wing plane to the other end of the plane, thus passing through the center of gravity of the equipment;

[0018] - The vertical axis or yaw axis passes through the center of gravity of the equipment from top to bottom and is perpendicular to the other two axes.

[0019] The front and rear, as well as the upstream and downstream, are defined relative to the direction of the aircraft's forward movement.

[0020] As previously stated, the lift propellers are longitudinally spaced by at least the chord length between the lift propellers on the fixed wing plane, and laterally spaced by the width between the lift propellers on the fuselage. The chord length is an imaginary line between the leading and trailing edges of the wing plane. The chord length between the propellers on the fixed wing plane is a chord length located in a vertical plane containing the axis of rotation of the propellers surrounding the wing plane. The width between the propellers on the fuselage is the maximum lateral dimension of the fuselage, measured in a vertical plane containing the axis of rotation of the propellers surrounding the fuselage. In some embodiments, the lift propellers are longitudinally spaced between 1.3 and 3 times the chord length, and / or, the lift propellers are laterally spaced between 1.3 and 3 times the width of the fuselage. The separation distance between two propellers is the distance between the closest ends of the propeller blades.

[0021] This separation between the lift propellers significantly reduces the mixing of propeller wakes below the aircraft, especially during low-speed flight. During transitional flight (from low-speed flight to cruise), the aerodynamic load on the lift propellers, resulting from the increased contribution of the fixed wing plane to lift, is reduced, thus greatly minimizing propeller / propeller wake interaction. During cruise, this interaction can be eliminated because the lift propellers can be stopped. Specifically, in some embodiments, the aircraft's control system is configured to rotate the lift propellers during low-speed flight and stop them during cruise.

[0022] As for the effect of the fixed-wing plane's wake on the lift propeller, it is almost non-existent in low-speed flight because the fixed-wing plane has a very small or no wake. The first effect is felt when the aircraft accelerates, i.e., at the beginning of the transition from low-speed flight to cruise flight. During this transition, the interaction between the fixed-wing plane and the propeller wake is relatively weak due to the lower lift of the fixed-wing plane. Finally, during cruise flight, this interaction is non-existent because the propeller is stopped and only the fixed-wing plane bears the weight of the aircraft.

[0023] Low-speed flight refers to hovering (stationary, with a speed of zero or near zero) or low-speed flight, i.e., flying at a speed below 56 km / h (30 knots). Cruise flight refers to flight at a speed higher than the following (the so-called minimum cruise speed, denoted as Vc min): at which the lift generated by the fixed wings completely offsets the weight of the aircraft.

[0024] The transition phase corresponds to the transition from low-speed flight to cruise flight and from cruise flight to low-speed flight.

[0025] In some implementations, the wingspan of at least one fixed wing plane in the fixed wing plane can vary between a maximum wingspan and a minimum wingspan, wherein the minimum wingspan is less than or equal to 50% of the maximum wingspan, and more particularly, the minimum wingspan is less than or equal to 40% of the maximum wingspan. A minimum wingspan equal to 50% of the maximum wingspan corresponds to a minimum wingspan that is half of the maximum wingspan.

[0026] At low speeds, the wingspan can be reduced to a minimum. The aircraft becomes more compact and has better wind resistance.

[0027] The main plane comprises paired wings with variable wingspan. Each wing is foldable, and the control system is configured to allow each wing to deploy laterally in the lateral direction. Therefore, the wingspan is changed laterally, i.e., along the aircraft's lateral axis. This in particular avoids the need for the wings to pivot in the horizontal plane and pass over the lift propeller, which would otherwise produce unfavorable aerodynamic interactions.

[0028] Each wing has a movable part and a fixed part. The fixed part is the near-end or central section of the wing that connects to the fuselage. The movable part is the distal or far-end section of the wing, that is, the part furthest from the fuselage.

[0029] The wing is foldable such that the movable end portion of the wing is positioned on the fixed portion (i.e., on top of the fixed portion) when folded. Therefore, folding the wing upwards limits its aerodynamic interaction with the propeller compared to folding laterally or downwards. Furthermore, folding upwards allows the wing to avoid contact with the ground when the control system operates to change the wingspan on the ground, compared to folding downwards.

[0030] In some implementations, the lift propeller includes two blades, and a control system is configured to bring the lift propeller to a stop position such that the blades are parallel to the longitudinal axis of the aircraft. When the propeller blades are positioned in this way, the direction of the propeller blades is the same as the direction of the fuselage, which reduces the aerodynamic drag of the aircraft during cruise flight.

[0031] In some implementations, the lift propeller is a twin-rotor propeller. This type of propeller, in particular, allows for a reduction in the diameter of the propeller rotor, thereby improving the compactness of the aircraft.

[0032] In some implementations, some lift propellers can be converted into propulsion propellers. This allows for a limitation on the number of propellers on board an aircraft. In particular, a propeller can have a lift function during one phase of flight, such as low-speed flight, and a propulsion function during another phase of flight, such as cruise flight. This dual use of lift propellers, due to the reduced number of propellers, makes the aircraft more compact and lighter.

[0033] The above and other features and advantages will become apparent after reading the following detailed description. This detailed description refers to the accompanying drawings. Attached Figure Description

[0034] The accompanying drawings are schematic and not necessarily drawn to scale; the drawings are primarily intended to illustrate the principles of the invention. In these drawings, the same elements (or parts thereof) are indicated by the same reference numerals from one figure to another.

[0035] [ Figure 1 This image shows an example of a VTOL aircraft as seen from the side.

[0036] [ Figure 2 This diagram shows the view from above. Figure 1 The example of a VTOL aircraft in the image shows the main fixed wing plane of the VTOL aircraft being deployed.

[0037] [ Figure 3 The image and Figure 2 Similar to the view in the image, the fixed wing plane is folded back. Detailed Implementation

[0038] The following will describe in detail specific embodiments of the provided aircraft with reference to the examples shown in the accompanying drawings. These embodiments illustrate the features and advantages of the invention. However, it should be noted that the invention is not limited to these embodiments or the examples shown.

[0039] In general, the provided VTOL aircraft includes a fuselage, at least one propulsion system, at least four lift propellers, and at least two fixed-wing planes. The aircraft can be a manned aircraft; or, the aircraft can be an unmanned aircraft, such as a drone.

[0040] In the example shown, the VTOL aircraft 1 includes a fuselage 2, a propulsion system 5, four lift propellers 10, and three fixed-wing planes 20, 30, and 40. The first fixed-wing plane 20 at the very front of the aircraft 1 is a canard configuration. The second fixed-wing plane 30, located in the middle section of the aircraft 1, is the main wing plane. The second fixed-wing plane 30 is of the wing pair type 32; in this example, the second fixed-wing plane 30 is composed of a right wing and a left wing joined together above the fuselage 2. The third fixed-wing plane 40, located at the rear of the aircraft 1, is called the rear wing plane and is of the tail type.

[0041] Four lifting propellers 10 are distributed on both sides of the fixed wing plane 30 and both sides of the fuselage 2. In other words, two lifting propellers 10 are located on the right side of the fuselage on both sides of the right wing 32 (i.e., in front of and behind the right wing 32), and two lifting propellers 10 are located on the left side of the fuselage on both sides of the left wing 32 (i.e., in front of and behind the left wing 32).

[0042] The left lift propeller 10 (i.e., the left front and left rear lift propellers 10) is longitudinally spaced by at least the chord length C1 between the left lift propellers on the fixed wing plane 30. The right lift propeller 10 (i.e., the right front and right rear lift propellers 10) is longitudinally spaced by at least the chord length C2 between the right lift propellers on the fixed wing plane 30.

[0043] The axis of rotation of propeller 10 is vertical. In the example, each lift propeller 10 is a double counter-rotating propeller.

[0044] Along the longitudinal direction, the propellers 10 are arranged in two rows: a front row and a rear row. The rear wing plane 40 is located behind the rear row. The lift propellers 10 in the front row (i.e., the right front and left front lift propellers) are laterally spaced at least by the width L1 between the lift propellers 10 in the front row of the fuselage 2. The lift propellers 10 in the rear row (i.e., the right rear and left rear lift propellers) are laterally spaced at least by the width L2 between the lift propellers 10 in the rear row of the fuselage 2.

[0045] The longitudinal axis X of aircraft 1 is in Figure 1 and Figure 2 The dashed line indicates the middle. Figure 2 The transverse axis Y shown is perpendicular to the longitudinal axis X and extends from one end of the main fixed wing plane 30 to the other end, thus passing through the center of gravity G of the aircraft. Figure 1 The vertical axis Z shown is perpendicular to axes X and Y and passes through the center of gravity G. The terms "down," "up," "top," "bottom," "above," and "below" refer to the height difference along the vertical axis.

[0046] The fixed wing planes, namely wing planes 30 and 40, located behind the foremost propeller 10 and above the assembly of lift propellers 10, are situated behind the front propellers 10 and above the assembly of lift propellers 10. Figure 1 As shown. This means that the lower surfaces (the parts below the wing) of the fixed wing planes 30 and 40 are located at a height higher than the highest rotational plane of the propeller 10. Figure 1 In the example, this means H2>Hl, where H2 is the height of the lowest lower surface and Hl is the height of the highest plane of rotation.

[0047] The fixed-wing plane 30 has a variable wingspan, and the aircraft 1 includes a control system, which is a group of onboard devices and mechanical, hydraulic, and / or electrical connections, used to change the wingspan of the wing plane 30 during flight. In the case of a VTOL unmanned aerial vehicle, this control system can be automatically controlled and / or remotely controlled. In the case of a manned VTOL aircraft, the control system can be automatically controlled and / or manually controlled from the cockpit. The control system is generally adapted to control according to the aircraft's flight rules to make the wingspan suitable for the flight phase. In some embodiments, the control system is configured to increase the wingspan when transitioning from low-speed flight to cruise flight and decrease the wingspan when transitioning from cruise flight to low-speed flight. Therefore, the aircraft can take off and land in confined areas with a reduced wingspan via the wing 32.

[0048] Each wing 32 is foldable to position the movable end portion 33 of the wing along and above the fixed portion 31 of the wing. Any folding in the middle (e.g., at a right angle) should be avoided to prevent wind load.

[0049] In the example shown in the figure, the movable end portion 33 of each wing 32 is foldable along the fold line 34.

[0050] exist Figure 2 In the middle, the movable part 33 is deployed laterally, and the wingspan of the wing 32 is the largest. Figure 3 In this configuration, the movable portion 33 folds backward, and the wingspan of the wing 32 is minimized. Each movable portion 33 folds backward from above and is positioned along and above the fixed portion 31.

[0051] In the example shown in the accompanying drawings, the propulsion system 5 of the aircraft is a propulsion propeller mounted at the forward end of the aircraft 1. Other propulsion systems 5 are contemplated, such as fans, turbojet engines, jet engines, or "small" propeller arrays for distributed propulsion. These propulsion systems can be positioned above the lifting propeller. In some embodiments, these propulsion systems are positioned on the highest fixed surface to reduce interaction with the lifting propeller; alternatively, these propulsion systems are mounted to the wing 32 by means of an offset shaft.

[0052] In some embodiments, each lift propeller 10 includes two blades 12 (and thus four blades 12 in the case of a twin propeller), and the control system is configured to stop the lift propeller 10 in a stationary position during cruise flight, such that the blades 12 are parallel to the longitudinal axis X of the aircraft to reduce the drag of the blades 12. For the same reason, in some embodiments, the blades 12 may be disengaged from the rotor so that one blade of the blades 12 is positioned above the other to reduce aerodynamic effects during cruise flight.

[0053] The following describes examples of optimized operation of the provided VTOL aircraft in different flight phases.

[0054] (1) Low-speed flight (including landing and takeoff):

[0055] During this flight phase, the VTOL aircraft 1 maneuvers to orient itself using the lift propeller 10 with a vertical axis. Therefore, the VTOL aircraft 1 can travel at speeds up to 56 km / h (30 knots) with the wings 32 folded. Consequently, the aircraft exhibits increased wind resistance due to the reduced wingspan of the foldable wings 32. The foldable wing system during low-speed flight ensures minimal overall size during takeoff and landing. For the same mass, most existing VTOL equipment is at least twice the size of the VTOL aircraft 1 during takeoff and landing.

[0056] (2) Transition phase:

[0057] After the wing 32 is deployed, the transition from low-speed flight to cruise flight is achieved by means of the propulsion system 5. During the transition, the lift propeller 10, with its vertical axis, remains in the horizontal plane of travel. This separation of the lift component and the propulsion component during the transition reduces the high-power maneuvering requirements of the lift propeller 10. The positioning of the lift propeller 10 allows for minimal aerodynamic interaction with the fixed surface. Most of the slipstream of the propeller 10 is cleared from the wing 32. Furthermore, since the propeller 10 is positioned below the plane of the wing 32, the impact is further reduced.

[0058] (3) Cruise flight:

[0059] During this flight phase, propeller 10 is stopped, and blades 12 are positioned along fuselage 2 to reduce drag. There is no interaction between the rotating and stationary surfaces.

[0060] The embodiments described in this specification are for illustrative purposes only and not for limiting purposes. Those skilled in the art can readily modify these embodiments or conceive of other embodiments based on this specification while remaining within the scope of the invention.

[0061] In particular, if some features of the previously described embodiments are sufficient on their own to provide one of the advantages of the invention, those skilled in the art will be able to readily conceive of alternatives that include only these features of the previously described embodiments. Furthermore, the different features of these embodiments can be used individually or in combination with each other. When the different features of these embodiments are combined, these features can be combined in the manner described above or in different ways, and the invention is not limited to the specific combinations described in this specification. In particular, unless otherwise stated, the features described in connection with one embodiment can be applied in a similar manner to another embodiment.

Claims

1. A vertical takeoff and landing aircraft, the aircraft comprising: fuselage (2); At least one propulsion system (5); Four lifting propellers (10); At least two fixed wing planes, the fixed wing planes including a main wing plane (30) and a rear wing plane (40) located at the rear of the aircraft. in, Both the main wing plane (30) and the rear wing plane (40) are located behind and above the foremost lifting propeller (10); The main wing plane (30) has a variable wingspan and includes a pair of wings (32), each of which is foldable along the lateral axis of the aircraft such that the movable end portion (33) of the wing is positioned along and above the fixed portion (31) of the wing when folded. The aircraft includes a control system for changing the wingspan of the main wing plane (30) in flight by causing each wing (32) to deploy laterally; The four lifting propellers (10) are distributed on both sides of the main wing plane (30) and on both sides of the fuselage (2). The two lifting propellers (10) located on the same side of the fuselage (2) are connected to the fixed portion (31) of the wing (32) located on that side of the fuselage (2), and the two lifting propellers (10) located on the same side of the fuselage (2) are longitudinally spaced at least by the size of the chord length (C1, C2) of the main wing plane (30) between the two lifting propellers (10) located on that side of the fuselage (2); as well as The two lifting propellers (10) located on the same side of the main wing plane (30) are spaced laterally at least by the width (L1, L2) between the two lifting propellers (10) on that side of the fuselage (2).

2. The aircraft according to claim 1, wherein, The control system is configured to rotate the lift propeller (10) during low-speed flight and to stop the lift propeller (10) during cruise flight.

3. The aircraft according to claim 1 or 2, wherein, The control system is configured to increase the wingspan when transitioning from low-speed flight to cruise flight and to decrease the wingspan when transitioning from cruise flight to low-speed flight.

4. The aircraft according to claim 1 or 2, wherein, The wingspan can vary between a maximum wingspan and a minimum wingspan, wherein the minimum wingspan is less than or equal to 50% of the maximum wingspan.

5. The aircraft according to claim 1 or 2, wherein, The wingspan can vary between a maximum wingspan and a minimum wingspan, wherein the minimum wingspan is less than or equal to 40% of the maximum wingspan.

6. The aircraft according to claim 1 or 2, wherein, The two lifting propellers (10) located on the same side of the fuselage (2) are longitudinally spaced between 1.3 and 3 times the size of the chord length (C1, C2).

7. The aircraft according to claim 1 or 2, wherein, The two lifting propellers (10) located on the same side of the main wing plane (30) are spaced laterally by a distance between 1.3 and 3 times the width (L1, L2) of the fuselage.

8. The aircraft according to claim 1 or 2, wherein, The two lift propellers (10) each include two blades (12), and the control system is configured to stop the lift propellers (10) in a stopped position such that the blades (12) are parallel to the longitudinal axis of the aircraft.

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