WO2021136901A1

WO2021136901A1 - Aircraft tail assembly comprising a control surface and fins for pressurising said control surface

Info

Publication number: WO2021136901A1
Application number: PCT/FR2020/052552
Authority: WO
Inventors: Sébastien Laurent Marie PASCAL
Original assignee: Safran Nacelles
Priority date: 2020-01-02
Filing date: 2020-12-18
Publication date: 2021-07-08
Also published as: FR3105967A1; FR3105967B1

Abstract

The invention relates to a vertical tail assembly (5) of an aircraft (1), the assembly being of the type comprising a vertical stabiliser (6) and a symmetry control surface (7), said tail assembly (5) comprising, on lateral surfaces of the vertical stabiliser (6), fins (20) which are configured to improve the supply of air to the control surface (7) during the landing phase, in particular so as to offset the lack of pressurisation resulting from a thrust reversal by reversers (8, 9) which are located upstream of said tail assembly (5).

Description

Title: Aircraft tail including a rudder and pressurization fins of this rudder

Technical area

The invention relates to the field of tail units for aircraft.

The invention is of particular interest when the aircraft is equipped with thrust reversers in the rear part of the fuselage, near the tail.

State of the prior art

There is shown in Figure 1 a conventional business aircraft 1 extending along a longitudinal axis A1. This aircraft 1 comprises a fuselage 2, two propulsion assemblies 3 mounted in the rear part of the fuselage 2 (a single propulsion assembly being visible in FIG. 1), a horizontal tail unit 4 and a vertical tail unit 5. The vertical tail unit 5 comprises a fixed part 6, also called fin, and a mobile part 7, also called rudder or symmetry. The fin 6 is intended to stabilize the aircraft 1 around a yaw axis A2, in particular in order to keep the longitudinal axis A1 parallel to the axis of the runway during the landing phase in the event of a crosswind (see below). The symmetry control surface 7 is intended to control the moment of the airplane 1 around the yaw axis A2, in particular to be able to keep the longitudinal axis A1 parallel to the axis of the runway during the landing phase.

Each of the propulsion units 3 comprises a thrust reverser having an upper door 8 and a lower door 9. In FIG. 1, the propulsion units 3 are in a direct thrust configuration in which the doors 8 and 9 are closed so as to close off. respective inversion openings (not shown in this figure).

FIG. 2 schematically represents the two propulsion assemblies (respectively referenced 3A and 3B) as well as the vertical stabilizer 5 with respect to said longitudinal axis A1 and to a relative wind A3. The relative wind A3 is the wind generated by the sum of the displacement of the airplane 1 and the wind. In figure 2, the propulsion units 3A and 3B are in a thrust reversal configuration in which said doors (not shown in this figure) are opened so as to release the corresponding reversing openings, namely an upper reversing opening 10A associated with the upper door of the reverser of the propulsion unit 3A and an upper reversal opening 10B associated with the upper door of the reverser of the propulsion unit 3B.

In a manner known per se, the doors of the propulsion units 3A and 3B in the thrust reversal configuration are configured to redirect in an upstream direction A4 part of the air leaving the propulsion units 3A and 3B through the reversal openings 10A / 10B.

FIG. 2 illustrates a landing situation in a crosswind, causing the airplane 1 to move around the yaw axis A2 so that its longitudinal axis A1 forms an angle B1 with the direction of the relative wind A3.

Under these conditions, the vertical stabilizer 5 is liable to be subjected to asymmetric air currents, in particular taking into account the respective trajectories of the air flows leaving the propulsion units 3A and 3B through the upper inversion openings 10A and 10B.

In fact, part of the air leaving the propulsion unit 3B, through the upper inversion opening 10B, typically flows along a path 11B passing through a region C1 extending along one of the faces of the vertical stabilizer 5 located on the side of this propulsion unit 3B. Part of the air leaving the propulsion unit 3A, through the upper inversion opening 10A, typically flows along a path 11A bypassing the fin 6 and also crossing the region C1. On the side of the propulsion unit 3A, a region C2 extending along the other face of the vertical stabilizer 5 is thus found to be under-supplied with air.

Independently of such asymmetric flows, the thrust reversal configuration results in a masking of an area situated downstream of the propulsion units 3 and a reduction in the air flow speeds and the dynamic pressure in the area thus masked. A typical masked zone C3 is shown in FIG. 3, in a plane perpendicular to the longitudinal axis A1. Zone C3 extends laterally up to the vertical stabilizer 5. Under such conditions, with reference to FIG. 4, the air forms current lines DI mainly supplying an upper zone El of the control surface 7. The air molecules present at a lower zone E2 of the control surface 7. tend to move towards the zones in which the speeds are greater, forming ascending flows D2 which join the current lines DI to finally reach the upper zone El of the control surface 7.

The control surface 7 thus devented at the level of its lower zone E2 and / or at the level of the lateral region C2 has a reduced efficiency liable to lead to a loss of controllability of the airplane 1 and potentially to an exit from the runway.

Disclosure of the invention

An object of the invention is to provide a tail unit making it possible to improve the controllability of an aircraft equipped with thrust reversers near the tail unit, when the reversers are in the thrust reversal configuration, in particular in the event of cross wind.

More generally, the invention aims to provide a tail unit making it possible to better distribute the air flows during the landing of the aircraft.

To this end, the invention relates to an aircraft comprising a fuselage, two propulsion units mounted in the rear part of the fuselage and a tail unit intended to ensure the stability of this aircraft around a yaw axis, each of the propulsion units comprising a thrust reverser, the tail unit comprising a fixed part and a movable part, the fixed part and the movable part extending in a vertical direction and each comprising two side surfaces intended to be subjected to a flow of a fluid exerting on those this is horizontal forces, the mobile part being configured to be able to be oriented so as to move the aircraft around the yaw axis under the action of said horizontal forces.

According to the invention, the tail unit comprises two fins, each fin being arranged in line with one respective one of the side surfaces of the fixed part and having a chord oblique or perpendicular to the vertical direction, each fin being positioned:

- vertically, at a distance of one root from the fixed part of the stabilizer between forty percent and sixty percent of a maximum height of the mobile part of the stabilizer and

- horizontally, so that a leading edge of this fin is at a distance from a rear end of the fixed part between a length of said chord and forty percent of a depth of this fixed part.

In the present description, it is understood that each fin has a leading edge, a trailing edge, an intrados and an extrados.

Conventionally, the chord of a fin is defined as a straight line joining the leading edge and the trailing edge of this fin.

A chord oblique or perpendicular to the vertical direction, that is to say not parallel to the vertical direction, has the consequence that the lower surface of the corresponding fin forms a surface capable of blocking or deflecting a flow of fluid having at least one component oriented vertically upwards.

The fins make it possible to better distribute the current lines so as to increase the fluid pressure applied to a lower zone of the mobile part of the tail unit despite the masking of this zone resulting from the thrust reversal.

In other words, the fins are configured so as to direct air flow lines towards a lower zone of the mobile structure hidden by the thrust reversers when the latter are in the thrust reversal configuration.

In fact, when the reversers are in the thrust reversal configuration, the fins make it possible to block part of the fluid flowing longitudinally towards the rear and vertically upwards, that is to say from a lower zone. from the fixed structure to an upper zone of the mobile structure. This part of the fluid, blocked by the lower surface of the fins, is therefore reoriented towards the lower zone of the mobile structure. This results in a better distribution of the horizontal forces on the lateral surfaces of the mobile part of the stabilizer and consequently an improvement in the controllability of the aircraft in the landing phase, including in a crosswind.

In one embodiment, each fin may include a proximal end and a distal end both located in the same horizontal plane.

Preferably, each fin can have a zero angle of incidence.

Conventionally, the angle of incidence is the angle formed by the chord of the fin and a relative wind speed vector.

In one embodiment, for each fin, the chord may have a length of between twenty-five percent and one hundred percent of an average depth of the movable part of the tail.

In one embodiment, each fin can have a wingspan of between ten percent and eighty percent of an average depth of the movable part of the tail.

Preferably, each fin may have a profile configured to minimize drag.

For example, each fin may have a curved mean line so as to minimize the drag produced by that fin.

The tail unit described above is a vertical tail unit since the latter is intended to ensure the stability of the aircraft around the yaw axis.

Of course, the aircraft can include both such a vertical stabilizer equipped with said fins and a horizontal stabilizer intended to ensure the stability of the aircraft around a pitch axis.

In this regard, the fins are in no way intended and do not contribute significantly to stabilizing the aircraft around the pitch axis.

The propulsion units can be mounted on either side of the fuselage, each upstream of a respective one of the fins, so that each of the fins has an impact. on the current lines in the masking zone produced by the corresponding propulsion unit.

Preferably, the thrust reverser of these propulsion units can be a door reverser.

Other advantages and characteristics of the invention will become apparent on reading the detailed, non-limiting description which follows.

Brief description of the drawings

The following detailed description refers to the accompanying drawings in which:

[Fig. 1] is a schematic view, already described above, of an aircraft of the prior art, this aircraft comprising a vertical tail unit and propulsion units each equipped with a thrust reverser with doors;

[Fig. 2] is a schematic view, already described above, of parts of the aircraft of FIG. 1 in the crosswind landing phase, the reversers being in a thrust reversal configuration;

[Fig. 3] is a schematic perspective view, already described above, of part of the aircraft of FIG. 1, this figure showing a masked zone downstream of one of the reversers in the thrust reversal configuration;

[Fig. 4] is a partial schematic view, already described above, of the aircraft of FIG. 1, this figure showing streamlines at the level of the vertical stabilizer when the reversers are in the thrust reversal configuration;

[Fig. 5] is a schematic view of an aircraft according to the invention, this aircraft comprising a vertical stabilizer provided with two fins and propulsion units each equipped with a thrust reverser with doors;

[Fig. 6] is a partial schematic view of the aircraft of FIG. 5, this figure showing current lines at the level of the vertical stabilizer when the reversers are in the thrust reversal configuration; [Fig. 7] is a schematic view of a cross section of one of the fins of the vertical stabilizer of the aircraft of FIG. 5.

Detailed description of embodiments

Figures 5 and 6 show an aircraft 1 according to the invention.

This aircraft 1 differs from that of Figures 1 to 4, described above, essentially in that the vertical tail 5 comprises two fins 20.

In this example, the fins 20 are fixed.

FIGS. 5 et seq. Comprise a frame of reference Z1, Z2 and Z3 respectively defining longitudinal, vertical and lateral directions.

The fixed part 6 and the mobile part 7 of the vertical stabilizer 5, that is to say the fin and the rudder of symmetry, extend in the vertical direction Z2 while the horizontal stabilizer 4 extends substantially in the lateral direction Z3.

In a manner known per se, the stabilizers 4 and 5 are in this example arranged in a T, the horizontal stabilizer 4 being positioned vertically at the top of the vertical stabilizer 5.

The fin 6 and the rudder 7 each comprise two side surfaces.

The side surfaces of the fin 6 extend in the longitudinal Z1 and vertical Z2 directions, so that an air flow having a component oriented in the lateral direction Z1 can exert horizontal forces on these side surfaces.

Such horizontal forces applied to the lateral surfaces of the fin 6 make it possible to stabilize the aircraft 1 around the yaw axis A2.

In a manner known per se, the rudder 7 is movable, relative to the fin 6, in rotation about an axis A5 (see FIG. 6). This axis of rotation A5 is located in a median longitudinal plane, or vertical plane, passing through the longitudinal axis Al of the aircraft 1 and being parallel to the directions Z1 and Z2. The axis of rotation A5 is also perpendicular to the lateral direction Zl. In an angular reference position, the rudder 7 is aligned with the fin 6 so that the lateral surfaces of the rudder 7 also extend in the longitudinal ZI and vertical Z2 directions.

By moving the rudder 7 around its axis of rotation A5, its side surfaces form an angle with the vertical plane, which makes it possible to reposition the aircraft 1 in the axis of the runway under the action of said horizontal forces applying on either of these side surfaces.

Concerning the fins 20, these are symmetrical with respect to one another relative to the vertical median longitudinal plane of the aircraft 1.

One of the fins 20 is arranged to the right of one of the side surfaces of the fin 6 while the other fin 20 is arranged to the right of the other side surface of the fin 6.

What is described below with reference to a single fin 20, which in this case corresponds to that visible in FIG. 6, applies in a similar manner to the other fin 20.

FIG. 7 shows the profile of the fin 20, that is to say a section of the fin 20 in a transverse plane Z1-Z2 parallel to the aforementioned vertical plane.

The fin 20 has a leading edge 21, a trailing edge 22, an intrados 23 and an extrados 24.

There is shown in Figure 7 two fictitious lines 30 and 31. The fictitious line 30 is a straight line joining the leading edge 21 and the trailing edge 22 and defining a chord of this fin 20. The fictitious line 31 is a line joining the leading edge 21 and the trailing edge 22, each point of which is equidistant from the lower surface 23 and the upper surface 24. The fictitious line 31 defines an average line of the fin 20.

The chord 30 of the fin 20, in the section of FIG. 7, is perpendicular to the vertical direction Z2.

In this example, the fin 20 is not twisted along the lateral direction Z3 so that the chord 30 is, in any cross section of this fin 20 parallel to said vertical plane, perpendicular to the vertical direction Z2. In other embodiments not shown, the chord 30 can, at least in certain cross sections parallel to this vertical plane, be oblique both with respect to the vertical direction Z2 and with respect to the longitudinal direction Z1.

In all cases, at least at the level of the root of the fin 20, the chord 30 is inclined with respect to the vertical direction Z2, that is to say that it is either oblique or perpendicular to this direction. vertical Z2.

Given such an orientation of the chord 30, the lower surface 23 of the fin 20 is able to redirect towards said lower zone E2 of the control surface 7 a significant part of a flow of air flowing, before meet the intrados 23, downstream and vertically upwards.

The chord 30 being in this example horizontal, the angle of incidence of the fin 20 is zero, considering the relative wind oriented parallel to the longitudinal direction Zl, which makes it possible to minimize the drag.

In the example of Figure 7, the midline 31 of fin 20 is curved, which also helps to minimize drag. The fin 20 can of course have a profile different from that of FIG. 7 without departing from the scope of the invention.

Referring to Figure 5, the fin 20 has a proximal end 40 and a distal end 41. The proximal end 40 is located at the root of this fin 20.

The proximal end 40 and the distal end 41 are here both located in the same horizontal plane parallel to the longitudinal Z1 and lateral Z3 directions. In other words, the fin 20 in this example extends horizontally in the lateral direction Zl.

The distance between the proximal end 40 and the distal end 41 defines a span XI of the fin 20.

Referring to Figures 5 and 6, the wingspan XI of the fin 20 is between ten percent and eighty percent of an average depth X2 of the rudder 7.

The depth X2 of the rudder 7 is the distance, in the longitudinal direction Zl, between a front end 50 and a rear end 51 of the rudder 7 measured in a horizontal plane Z1-Z3. The front end 50 of the rudder 7 is located at its axis of rotation A5, facing a rear end 52 of the fin 6. The rear end 51 of the rudder 7 defines a trailing edge of the rudder 7 and more generally a downstream end of the vertical stabilizer 5.

In this example, the depth X2 is substantially identical over the entire span of the stabilizer 5. In other embodiments not shown, this depth X2 can vary in the vertical direction Z2.

Referring to Figures 6 and 7, the chord 30 of the fin 20 has a length X0 of between twenty-five percent and one hundred percent of the average depth X2 of the rudder 7.

Concerning the position of the fin 20 on the fin 6, it is considered a height X3 of the rudder 7 and a depth X4 of the fin 6 (see FIG. 6). In this example, the height X3 is the distance, in the vertical direction Z2, between a lower end 60 and an upper end 61 of the control surface 7.

The upper end 61 of the rudder 7 is delimited by an inner face of the horizontal tail 4.

The lower end 60 of the rudder 7 is located in the extension of a lower end 63 of the fin 6, at the root of this fin 6.

The depth X4 of the fin 6 is the distance, in the longitudinal direction Zl, between a front end 62 and said rear end 52 of this fin 6 measured in a horizontal plane Z1-Z3.

The front end 62 of the fin 6 forms a leading edge of the vertical stabilizer 5.

Vertically, the fin 20 of FIG. 6 is positioned at a distance X5 from the root of the fin 6 comprised between forty percent and sixty percent of the maximum height X3 of the rudder 7.

This positioning can be achieved by establishing said distance X5 between, on the one hand, the leading edge 21 of the fin 20 and, on the other hand, a point of the root of the fin 6 passing through a parallel straight line. in the vertical direction Z2 and passing through the leading edge 21 of the fin 20. Horizontally, the fin 20 of FIG. 6 is positioned upstream of the rudder 7, more precisely so that the leading edge 21 of this fin 20 is at a distance X6 from the rear end 52 of the fin 6 included. between the value of the length X0 of the chord 30 of this fin 20, in which case the trailing edge 22 of the fin 20 is at a zero distance from the rear end 52 of the fin 6, and forty percent of the depth X4 of fin 6, depth X4 being considered here in a horizontal plane Z1-Z3 passing through fin 20.

During the landing phase, the doors 8 and 9 of the thrust reversers of the propulsion units 3A and 3B are open and generate the masking phenomenon described above with reference to FIG. 3.

Under such conditions, the fins 20 make it possible to distribute the current lines over the majority of the height X3 of the rudder 7 so as to effectively pressurize the lateral surface of the fin 6 and of this rudder 7 on which it is necessary to applying horizontal forces in order to reposition the aircraft 1 around the yaw axis A2 and to guarantee sufficient stability of the aircraft 1 around this yaw axis A2.

In particular, the fins 20 make it possible to define current lines D3 satisfactorily supplying the lower part E2 of the control surface 7 (see FIG. 6), including in the event of a crosswind.

In other words, the fins 20 are configured so as to direct the lines of air current towards a lower zone of the control surface 7 masked by the reversers when the latter are in the thrust reversal configuration.

The invention is not limited to the specific examples which have just been described. In particular, in embodiments not shown, the thrust reversers can be gate reversers.

Claims

1. Aircraft (1) comprising a fuselage (2), two propulsion units (3A, 3B) mounted in the rear part of the fuselage (2) and a tail unit (5) intended to ensure the stability of this aircraft (1) around it. a yaw axis (A2), each of the propulsion units (3A, 3B) comprising a thrust reverser, the tail unit (5) comprising a fixed part (6) and a movable part (7), the fixed part (6) and the movable part (7) extending in a vertical direction (Z2) and each comprising two side surfaces intended to be subjected to a flow of a fluid exerting horizontal forces thereon, the movable part (7) being configured to be able to be oriented so as to move the aircraft (1) around the yaw axis (A2) under the action of said horizontal forces, the tail (5) being characterized in that it comprises two fins ( 20), each fin (20) being arranged in line with one respective one of the side surfaces of the fixed part (6) and having a chord (30) obliquely e or perpendicular to the vertical direction (Z2), each fin (20) being positioned:

- vertically, at a distance (X5) from a root (63) of the fixed part (6) of the tail (5) between forty percent and sixty percent of a maximum height (X3) of the part mobile (7) of the empennage (5) and

- horizontally, so that a leading edge (21) of this fin (20) is at a distance (X6) from a rear end (52) of the fixed part (6) between a length (X0) of said cord (30) and forty percent of a depth (X4) of this fixed part (6).

2. Aircraft (1) according to claim 1, wherein each fin (20) comprises a proximal end (40) and a distal end (41) both located in the same horizontal plane.

3. Aircraft (1) according to claim 1 or 2, wherein each fin (20) has a zero angle of incidence.

4. Aircraft (1) according to any one of claims 1 to 3, wherein, for each fin (20), the cord (30) has a length (X0) of between twenty-five percent and one hundred percent d 'an average depth (X2) of the moving part (7) of the tail (5).

5. Aircraft (1) according to any one of claims 1 to 4, wherein each fin (20) has a wingspan (XI) of between ten percent and eighty percent of an average depth (X2) of the mobile part (7) of the stabilizer (5).

6. Aircraft (1) according to any one of claims 1 to 5, wherein each fin (20) has an average line (31) curved so as to minimize the drag produced by this fin (20).

7. Aircraft (1) according to any one of claims 1 to 6, wherein the thrust reverser of each of the propulsion units (3A, 3B) is a door reverser (8, 9).