WO2020025885A1

WO2020025885A1 - Vertical take-off and landing aircraft

Info

Publication number: WO2020025885A1
Application number: PCT/FR2019/051848
Authority: WO
Inventors: Gaetan CHESNEAU
Original assignee: Safran
Priority date: 2018-08-02
Filing date: 2019-07-25
Publication date: 2020-02-06
Also published as: FR3084647B1; FR3084647A1

Abstract

The invention concerns a vertical take-off and landing aircraft (10, 11, 13, 15) comprising a fuselage (12) above which at least one lift rotor (24) is arranged, characterised in that it comprises at least a first propeller (26) and a second propeller (28), each carried by a tail (16) and hinged thereto in such a way as to be able to move between at least one first position in which it is capable of acting as an anti-torque rotor and at least one second position in which it is capable of providing thrust propelling the aircraft (10, 11, 13, 15) in a forward direction, the rotation axes (26a, 28a) of the first propeller (26) and the second propeller (28) being substantially coaxial when the first propeller (26) and the second propeller (28) are in their first position.

Description

TAKE-OFF AND VERTICAL LANDING AIRCRAFT

FIELD

The present invention relates to a vertical take-off and / or landing aircraft known by the acronym VTOL (Vertical Take-off and Landing aircraft).

CONTEXT

Such an aircraft is conventionally equipped with at least one lift rotor. The term "rotor" or "lift rotor" here covers the rotors used for helicopters and tilting propellers, in particular, and more generally any rotor with non-faired blades.

Takeoff and vertical landing are characteristics regularly taken into account on different flying means of transportation (here aircraft), because they make it possible to dispense with the take-off runway and / or to be able to land on restricted spaces. even unprepared and therefore potentially evolve in town.

Helicopters have this characteristic with their main rotor. However, this limits cruising performance with speeds not exceeding 300 km / h. The take-off and / or vertical landing constraint and / or displacements along substantially the vertical axis make it necessary to generate a vertical thrust, while flight in "airplane" mode - privileged axis of displacement then supposed to be horizontal, to create a thrust in the opposite direction to this privileged advance direction -, much more effective for traveling distance, requires horizontal thrust.

Thus, helicopters with hybrid configuration are known, also called combined since they comprise, in addition to the lift rotor, lateral lift wings or propulsion means according to the direction of advance. This type of machine optimizes the operating in stationary mode and improving capacities at high speeds as well as transitions while having an optimal structural architecture to minimize weight, increase comfort and improve safety. However, the implementation is complex and costly.

[006] Thus, this explains why the simple helicopter formula comprising at least one lift rotor and an anti-torque tail rotor has imposed itself despite the fact that the maximum speed is less than the speed of a combined or convertible type.

Improved solutions of hybrid formulas have been proposed but they complicate the technical achievements and imply increases in mass which impose an increase in the installed power and therefore in cost, without however achieving satisfactory optimization of the device. .

Regarding so-called combined aircraft, half-wings on either side of the fuselage make it possible to increase the load factor and achieve higher maneuverability. This improves the efficiency of the aircraft at medium speed at the expense of reduced efficiency at low speed and in stationary mode. As the lift during cruise is produced simultaneously by the rotor and the wings, this aircraft therefore overcomes the limits of lift of the rotor by means of the wings and the limits of thrust of the rotor by means of propellers. The use of propellers distributed on either side of the fuselage makes it possible to perform the anti-torque function at low speed (vertical and hovering flights).

In comparison with airplanes, the power required and the mass of the propulsion system of a helicopter are two to three times greater than that of a plane with the same MTOW (Max Take Off Weight) because a VTOL needs power to lift its own weight, whereas an airplane must only counter the aerodynamic drag which is a fraction of its own weight. On convertibles (VTOL), the lift is produced 100% by the rotors in VTOL mode and 100% by the wings in forward flight mode (airplane). In Consequently, the convertibles are overpowered in horizontal flight leading to lower efficiency than an airplane. In addition, the stiffness of the rigid blades, the tilting mechanism of the rotors and the motors, and the design of the wings producing 100% lift in forward flight lead to an increase in weight which greatly reduces the efficiency of the convertibles in horizontal modes. and vertical.

[010] Hybrid helicopters are also known, comprising a lift rotor and two lateral propellers in a forward direction. These propellers are positioned at the ends of the arms connected to an upper part of the fuselage under the lift rotor. Given the safety constraints in the event of a fall, the cabin must be stiff and strong enough to react without deformation to the inertial forces which increase in the event of a collision with the ground at vertical speed. This requirement leads to having a high structural mass and reducing the cabin space. For combined aircraft, this is compounded by the weight of the wings and engines that are attached to the root. In addition, on conventional handsets, the propellers must operate in the turbulent zone under the rotor reducing their efficiency and increasing the generation of noise. The location of non-faired propellers near the cabin requires the use of additional structural equipment, a source of mass increase in the event of blades bursting. Finally, the open propellers being placed next to the passenger access doors to the cabin, it generates obvious safety problems when boarding / disembarking passengers and increases the noise felt inside the cabin.

In another version of the above-mentioned handset, the propellers are arranged at the end of the lift wing, the ends of said wings being substantially aligned with the rear plane of the aircraft. However, this type of handset can be tricky to maneuver in the event of a heavy attitude and damage to one of the propellers.

In yet another version of an aircraft, it has been proposed to have two non-faired propellers at the ends of the arms lateral positioned at the upstream end of the fuselage, the lift wings being as described in the previous paragraph. The propellers can be pivoted between a first lift position and a second propulsion position. This gives this aircraft better hover capacity and better cruise capacity than a handset. But this is interesting, the following disadvantages exist:

- the diameter of the propellers is small to ensure a high-speed propulsion function, that is to say greater than 450 km / h, while a larger diameter, with adjustable propellers, is likely to pose relatively problems ground clearance, and

- the anti-torque function must be ensured by at least one of the propellers and to produce a horizontal differential thrust (while the management of this differential thrust is not easy to deal with).

In view of the previous presentation, if the idea of a combined with two propellers (faired or not) distributed on each side of the longitudinal axis of the fuselage, and fixed at the end of two half wings, is attractive for the reasons mentioned initially, the embarkation / disembarkation of passengers with the rotating propellers, even with propellers positioned on the trailing edge of the half-wings rather than on the leading edge, remains dangerous because of the risks of human aspiration near the fuselage.

It is therefore understood that there is a need for a convertible handset offering optimal safety conditions for the boarding of passengers.

SUMMARY OF THE INVENTION

The present invention relates firstly to an aircraft with vertical takeoff and landing comprising a fuselage above which is arranged at least one lift rotor, characterized in that it comprises at least a first propeller and a second propeller each carried by a shank and articulated in displacement thereon between at least a first position in which the propeller considered is suitable for serving as an anti-torque rotor and at least one second position in which the propeller considered is capable of allowing a propulsion thrust of the aircraft in a direction of advance, the axes of rotation of said first propeller and second propeller being substantially coaxial when said first propeller and second propeller are in their first position.

According to the invention, the aircraft comprises two propellers positioned on the tail and articulated in movement between two positions, which makes it possible to perform the anti-torque function when the propellers are in their first position and to perform the function of propulsion in their second position. Each propeller is able to move from its first position to its second position independently of the other propellers. The movement of the propellers between the first position and the second position allows boarding of passengers or loading of cargo with the first propeller and the second propeller in their first position, which prevents the propellers from presenting a risk of aspiration for a passenger. a ground operator. The aircraft according to the invention thus makes it possible to increase the operating capacities in helicopter mode and the capacities in airplane mode while increasing safety. There will also be a reduced footprint favoring access for service personnel for fueling or maintenance operations.

Only one of the first propeller and the second propeller can be used when the first propeller and the second propeller are in their first position. Thus, this single propeller ensures the anti-torque function, the other propeller ensuring a redundancy of the anti-torque function. This is particularly interesting since an essential function of the helicopter mode is thus doubled, certainly with an addition of mass but the two propellers are however used in advance propulsion mode. In a first variant, each of the two propellers can have a fixed rotation speed and have a variable collective pitch which varies the thrust for a given diameter and a twisted blade. In a second variant, each of the two propellers has a fixed pitch and it is the variation in the rotation speed which makes the variation in thrust for a given diameter and twist of the blade. A third variant can combine the two systems at the expense of being more overweight. Each of the propellers can be electrically powered by an electrical power bar which can itself be powered by the generator of the main engine of the aircraft or that of the second engine or that of a dedicated battery. The first and second propellers can rotate in the same direction or in opposite directions.

[019] The propellers can take other positions other than the first and second positions.

In a particular embodiment, the first propeller and the second propeller can be arranged in a substantially symmetrical manner with respect to one plane containing the longitudinal axis of the aircraft and the axis of the rotor of lift. It is thus understood that such a position allows an anti-torque function when the propellers are in their first position and a propulsion in their second position.

According to a feature of the present description, said first and second propellers are mounted at one end of an arm, the other opposite end of which is articulated in rotation on the tail of the aircraft.

[022] In fast forward flight, the two lever arms are held in their second position thanks to a dedicated mechanism such as a mechanical locking finger known in particular in an automatic gearbox parking brake in an automobile, in complement of a worm-type tilting mechanism connected to a stepper motor. Each of the two tail propellers can be connected to an electric motor and offers a propulsion capacity which advantageously blows the profile. a stabilization and maneuvering surface, which improves aerodynamic efficiency and therefore its lift capacity for a given span / width.

[023] In one embodiment, the axis of rotation of each arm is arranged longitudinally between the propeller and the downstream end of the tail when the propeller is in its first position. The propellers are thus arranged at a distance at least equal to that of the lever arms of a stabilization and downstream maneuvering plane when the propellers are in the first position.

In this configuration, the propellers can be positioned under the lift rotor when the propellers are in their second position.

In another embodiment, each propeller is arranged longitudinally between the axis of rotation of the articulation of the arm and the downstream end of the tail when the propeller is in its first position, which makes it possible to move the lift rotor propellers and increases the efficiency of the aircraft.

[026] In one embodiment of the invention, said first and second propellers are articulated in displacement over an angular distance of approximately 90 ° so that the axis of rotation of each of the first and second propellers is substantially parallel to the longitudinal axis of the aircraft, when the propellers are in their second position.

According to a characteristic of the application, the diameter of the first and second propellers is such that the circle circumscribed at the radially outer ends of the blades of each of the propellers intercepts the outer contour of the fuselage of the aircraft when the aircraft is seen from upstream downstream along the longitudinal axis.

[028] Also, the distance between the axes of said first propeller and second propeller can be less than the transverse dimension of the stabilization and maneuvering surface. [029] Also, the diameter of the first and second propellers may be such that the circle circumscribed at the radially outer ends of the blades of each of the propellers does not intercept the outer contour of the fuselage of the aircraft when the aircraft is seen from l upstream downstream along the longitudinal axis. In this configuration, the propellers are then provided with a smaller diameter than in the precast embodiment. The distance between the axes of said first propeller and second propeller can thus be greater than the transverse dimension of the stabilization and maneuvering surface.

The invention also relates to a method of passing the aircraft, as described above, from a slow-forward configuration to a fast-forward configuration, in which it comprises the following successive steps:

The first propeller being in anti-torque operation, the second propeller is moved from its first position to its second position, - The second propeller is put into operation so as to provide thrust in the longitudinal direction,

The rotation of the first propeller is stopped,

The first propeller is moved from its first position to its second position,

- The first propeller is put into operation so as to provide thrust in the longitudinal direction.

[031] The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of nonlimiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 A is a schematic view from above of an aircraft according to a first embodiment, the propellers being in a first position; Figure 1B is a schematic top view of an aircraft according to the first embodiment, the propellers being in a second position;

FIGS. 2A, 2B, 2C and 2D are schematic views from above, successively illustrating the transition from helicopter mode to airplane mode of the aircraft described with reference to FIGS. 1A and 1B;

Figure 3A is a schematic view from upstream of an aircraft such as that of Figures 1A and 1B, for example, the propellers being in their first position;

FIG. 3B is a schematic view from upstream of an aircraft such as that of FIGS. 1A and 1B, for example, the propellers being in their second position, having a first diameter and being arranged upstream of a surface of stabilization and maneuver;

FIG. 3C is a schematic view from upstream of an aircraft such as that of FIGS. 1A and 1B, for example, the propellers being in their second position, having a second diameter smaller than the first diameter and being arranged laterally on the side on the other side of the stabilization and maneuvering surface;

Figures 4A and 4B show another embodiment in which the propellers are arranged near a stabilization and maneuvering surface;

FIGS. 5A and 5B represent yet another embodiment in which the tail has no stabilization and maneuvering surface.

DETAILED DESCRIPTION [032] First of all, reference is made to FIGS. 1A and 1B which represent a first embodiment of an aircraft 10 comprising a fuselage 12 comprising a part forming a cabin 14 for transporting passengers or freight and a part forming a tail 16 extending downstream from the cabin 14 and connected at its downstream end to a surface 18 of stabilization and maneuvering comprising a rear tail unit comprising two fins 20, 22 for longitudinal control of the aircraft 10. The longitudinal axis of the aircraft 10 is shown at A in the various figures.

The aircraft 10 comprises a main lift rotor 24 mounted above the cabin 14. This rotor 24 is entirely conventional and will not be described in more detail.

[034] As is well represented, the aircraft 10 comprises a first propeller 26 and a second propeller 28 each mounted at a first end of a movable arm 30, 32 the second end of which is articulated in rotation on the tail 16 of the aircraft 10. Each propeller 26, 28 can be articulated by a dedicated electric motor or by means already present in the aircraft 10. Each propeller 26, 28 has an axis of rotation 26a, 28a.

The axis of rotation 34, 36 of each arm 34, 36 is perpendicular to the longitudinal axis A of the aircraft 10 and is substantially parallel to the axis of rotation 24a of the main lift rotor 24. Each arm 30, 32 is articulated in rotation between a first position in which the first propeller 26 or the second propeller 28 is capable of serving as an anti-torque rotor, the axes of rotation 26a, 28a of the propellers 26, 28 being coaxial, and a second position in which the first propeller 26 and the second propeller 28 are capable of allowing propulsion of the aircraft 10 in a direction of advance, the axes 26a, 28a of the propellers being parallel to the longitudinal axis A. More particularly , the first propeller 26 and the second propeller 28 are arranged in a manner substantially symmetrical to one another with respect to a plane containing the longitudinal axis A of the aircraft 10 and the axis 24a of the lift rotor 24. It is observed that this symmetry is achieved when the propellers 26, 28 are in their first and second positions.

In this first embodiment, the first propeller 26 and the second propeller 28 are each positioned relative to their respective axis 34, 36 of rotation so that the propeller 26, 28 is arranged longitudinally between the axis 34, 36 of rotation and the downstream end of the tail 16 plus specifically the stabilization and maneuvering surface 18. In this configuration, in order to be moved from the first position to the second position, the first propeller 26 and the second propeller 28 therefore performs a rotational movement upstream of the aircraft 10. More particularly, the rotational movement of the first propeller 26 or right propeller is a clockwise and upstream movement and the rotational movement the second propeller 28 or left propeller is a rotation movement counterclockwise and upstream. It is also observed that the propellers 26, 28 are arranged under the lift rotor 24 when the propellers 26, 28 are in their second position.

[037] Although only two positions of the propellers 26, 28 have been described, it is understood that each of these can take intermediate positions.

To achieve a passage of each of the propellers 26, 28 from its first position to its second position so that the aircraft 10 passes from a helicopter configuration where at least one of the first propeller 26 and the second propeller 28 is rotatable to perform an anti-torque function in an airplane configuration where the first propeller 26 and the second propeller 28 provides propulsion in a direction of advance, the procedure is as follows. Firstly, the first propeller 26 being in anti-torque operation, the second propeller 28 which is not in operation is moved from its first position to its second position (FIG. 2A). The first propeller 26 is then stopped and the second propeller 28 is put into operation so as to provide advance propulsion (FIG. 2B and FIG. 2C). The first propeller 26 is then moved to its second position (Figure 2D) and then put into operation to provide propulsion (Figure 2D).

[039] Figure 3A shows an aircraft 10 similar to that of Figures 1 A and 1 B which comprises two propellers 26, 28 arranged to move between a first position and a second position as described above. In FIG. 3A, the first propeller 26 and the second propeller 28 are in their first position, which explains why they are not visible since the arms 30, 32 are aligned with the longitudinal axis A and hidden by the fuselage 12. FIG. 3B represents an embodiment in which the diameter of the first propeller 26 and of the second propeller 28 is such that the circle 38 circumscribed at the radially outer ends of the blades of each of the first propeller 26 and of the second propeller 28 intercepts the external contour of the fuselage of the aircraft 10 when the latter is seen from upstream to downstream along the longitudinal axis A. In practice, it is understood that the propellers 26, 28 obviously do not penetrate into the fuselage since the latter has a section which reduces when going towards the downstream. The distance between the axes 26a, 28a of said first propeller 26 and second propeller 28 is less than the transverse dimension of the surface 18 for stabilization and maneuver. More particularly, the axis 26a, 28a of rotation is of each of the propellers 26, 28 is here substantially aligned with a fin 20, 22 when the propeller 26, 28 is in its second position.

[040] FIG. 3C represents another embodiment of an aircraft

11 embodiment in which the diameter of the first propeller 26 and of the second propeller 28 is such that the circle 40 circumscribed at the radially outer ends of the blades of each of the first propeller 26 and of the second propeller 28 does not intercept the outer contour of the fuselage 12 of the aircraft 11 when the aircraft 11 is seen from upstream to downstream along the longitudinal axis A. The distance between the axes 26a, 28a of said first propeller 26 and second propeller 28 is here greater than the transverse dimension of the stabilization and maneuvering surface 18. In other words, the axes 26a, 28a of rotation of the propellers 26, 28 are located on either side of the surface 18 for stabilization and maneuver in a transverse direction, that is to say perpendicular to a plane containing l 'longitudinal axis A and the axis 24a of rotation of the main rotor 24. It is also noted that in this embodiment, the diameter of the propellers 26, 28 is less than the diameter of the propellers of the embodiment shown in Figure 3B. [041] In another embodiment of an aircraft 13 shown in Figures 4A and 4B, the first propeller 26 and the second propeller 28 are each positioned relative to the axis 34, 36 of the arm 30, 32 so that the axis 34, 36 of rotation is arranged longitudinally between the propeller 26, 28 and the downstream end of the tail 16, more specifically the surface 18 of stabilization and maneuver. In this configuration, to be moved from the first position to the second position, the first propeller 26 and the second propeller 28 therefore perform a rotational movement downstream of the aircraft 13. More particularly, the rotational movement of the first propeller 26 or right propeller is a rotational movement counterclockwise and downstream and the rotational movement of the second propeller 28 or left propeller is a rotational movement clockwise and downstream. It is also observed that the propellers 26, 28 are not arranged under the lift rotor when the propellers 26, 28 are in their second position so that the influence of the rotor 24 is reduced compared to the embodiment shown in FIGS. 1A and 1 B. The first propeller 26 and the second propeller 28 are arranged in the downstream extension of the stabilization and maneuvering surface 18 as has been described with reference to FIG. 3B. It is understood that the propellers 26, 28 could also be arranged on either side of the stabilization and maneuvering surface 18 as illustrated in FIG. 3C.

[042] Figures 5A and 5B shows an aircraft 15 similar to that of Figures 4A and 4B with the difference that the downstream end of the tail has no surface 18 for stabilization and maneuvering. It can be seen that the first propeller 26 and the second propeller 28 are not arranged under the lift rotor when they are in their second position.

[043] In a particular embodiment, the first propeller 26 and the second propeller 28 are articulated in rotation over a stroke of 90 ° so that the axes 26a, 28a of the propellers 26, 28 are substantially parallel to the longitudinal axis A when the propellers 26, 28 are in their second position.

Claims

1. Aircraft (10, 1 1, 13, 15) with vertical takeoff and landing comprising a fuselage (12) above which is arranged at least one lift rotor (24), characterized in that it comprises at least one first propeller (26) and a second propeller (28) each carried by a shank (16) and articulated in displacement thereon between at least a first position in which it is able to serve as an anti-torque rotor and at least one second position in which it is capable of allowing a propulsion thrust of the aircraft (10, 1 1, 13, 15) in a direction of advance, the axes (26a, 28a) of rotation of said first propeller (26) and second propeller (28) being substantially coaxial when said first propeller (26) and second propeller (28) are in their first position.

2. Aircraft according to claim 1, in which the first propeller (26) and the second propeller (28) are arranged in a manner substantially symmetrical to each other with respect to a plane containing the longitudinal axis (A) of the aircraft (10) and the axis (24a) of the lift rotor (24).

3. Aircraft according to claim 1 or 2, in which said first and second propellers (26, 28) are mounted at one end of an arm (30, 32) whose opposite opposite end is articulated in rotation on the tail ( 16) of the aircraft (10).

4. Aircraft according to claim 3, in which the axis (34, 36) of rotation of the articulation of each arm (30, 32) is arranged longitudinally between the propeller (26, 28) and the downstream end of the tail (16) when the propeller (26, 28) is in its first position.

5. Aircraft according to claim 3, in which each propeller (26, 28) is arranged longitudinally between the axis (34, 36) of rotation of the arm (30, 32) and the downstream end of the tail (16) when the propeller (26, 28) is in its first position.

6. Aircraft according to one of claims 1 to 5, wherein said first and second propellers (26, 28) are articulated in displacement over an angular distance of approximately 90 ° so that the axis of rotation of each of the first propeller (26) and second propeller (28) is substantially parallel to the longitudinal axis (A) of the aircraft (10 ).

7. The aircraft as claimed in claim 1, in which the downstream end of the tail (16) comprises at least one stabilization and maneuvering surface (18).

8. Aircraft according to one of claims 1 to 7, in which the diameter of the first and second propellers (26, 28) is such that the circle circumscribed at the radially outer ends of the blades of each of the propellers (26, 28) intercepts the external contour of the fuselage (12) of the aircraft when the aircraft is seen from upstream to downstream along the longitudinal axis (A).

9. Aircraft according to claims 7 and 8, in which the distance between the axes (26a, 28a) of said first propeller (26) and second propeller (8) is less than the transverse dimension of the surface (18) for stabilization and maneuver.

10. Aircraft according to one of claims 1 to 7, in which the diameter of the first and second propellers (26, 28) is such that the circle circumscribed at the radially outer ends of the blades of each of the propellers (26, 28) does not not intercept the external contour of the fuselage (12) of the aircraft when the aircraft (11) is seen from upstream to downstream along the longitudinal axis (A).

11. Aircraft according to claims 7 and 10, in which the distance between the axes (26a, 28a) of said first propeller (26) and second propeller (28) is greater than the transverse dimension of the surface (18) for stabilization and maneuver.

12. Aircraft according to one of the preceding claims, in which one and / or the other of the first propeller (26) and of the second propeller (28) are articulated in movement by means of an electric motor.

13. The method of passing the aircraft according to one of claims 1 to 10 from a slowly advancing configuration to a fast forward configuration, in which it comprises the following successive steps:

The first propeller (26) being in anti-torque operation, the second propeller (28) is moved from its first position to its second position,

The second propeller (28) is put into operation so as to provide thrust in the longitudinal direction (A),

The rotation of the first propeller (26) is stopped,

The first propeller (26) is moved from its first position to its second position,

The first propeller (26) is operated to provide thrust in the longitudinal direction (A).