FR3061146A1 - REAR-ENGINE AIRCRAFT HAVING AT LEAST ONE ARM IN A REJECTED POSITION REAR AND REMOTE FROM AN AIR END OF THE AIRCRAFT CELL - Google Patents

Abstract

To optimize the performance of an aircraft by maximizing the ability of ingestion of the boundary layer by a rear engine, there is provided an aircraft (10) comprising a cell (12) and at least one rear engine (34), the cell (12) being extended by at least one arm (30A, 30B) which carries the rear motor (34) and maintains it offset back and away from a rear end (32) of the cell (12) defined on an axis longitudinal axis (37) of the rear engine (34).

Description

© Holder (s): AIRBUS OPERATIONS Simplified stock company.

by

O Extension request (s):

Agent (s): BREVALEX Limited liability company.

FR 3 061 146 - A1 (54) AIRCRAFT WITH REAR ENGINE CARRIED BY AT LEAST ONE ARM IN A SHIFT POSITION REAR AND AT A DISTANCE FROM A REAR END OF THE AIRCRAFT CELL.

(57) To optimize the performance of an aircraft by maximizing the ability to ingest the boundary layer by a rear engine, an aircraft (10) is proposed comprising a cell (12) and at least one rear engine (34) , the cell (12) being extended by at least one arm (30A, 30B) which carries the rear motor (34) and keeps it offset behind and at a distance from a rear end (32) of the defined cell (12) on a longitudinal axis (37) of the rear engine (34).

AIRCRAFT WITH REAR ENGINE CARRIED BY AT LEAST ONE ARM IN AN OFFSET POSITION REAR AND REMOTE FROM A REAR END OF THE AIRCRAFT CELL

DESCRIPTION

TECHNICAL AREA

The present invention relates generally to the field of aircraft.

It is known that ingestion, by an aircraft engine, of the boundary layer, that is to say the flow of air with low kinetic energy located in the immediate vicinity of the aircraft cell, reduces the energy spent on propulsion as well as the drag of the aircraft, with the consequence of a reduction in fuel consumption.

The invention thus relates more particularly to the field of aircraft equipped with an engine arranged so as to ingest at least part of the boundary layer formed along the airframe of the aircraft.

PRIOR STATE OF THE ART

It is known to bring back, in a rear part of an aircraft cell, engines powered by ingestion of the boundary layer. These are, for example, two semi-buried motors arranged side by side, projecting upwards or laterally from the rear part of the aircraft cell.

However, in this type of configuration, the two motors allow only part of the air in the boundary layer circulating on the rear part of the aircraft cell to be ingested. For these configurations, the boundary layer is also ingested in a non-axisymmetric manner with respect to the axis of the air inlet, thus generating a distortion of the flow at the inlet of the engine.

There is therefore a need for optimization aimed at benefiting more from the principle of propulsion by ingestion of the boundary layer.

STATEMENT OF THE INVENTION

The invention provides for this purpose an aircraft, comprising a cell and at least one rear engine. According to the invention, the cell is extended by at least one arm which carries the rear motor and keeps it offset behind and at a distance from a rear end of the cell defined on a longitudinal axis of the rear motor.

The rear engine is thus arranged facing a rear end part of the aircraft cell, and is thus able to ingest at least part of the air of the boundary layer circulating on the periphery of the cell, in a substantially axisymmetric manner. The invention thus allows a reduction in the overall drag of the aircraft. The rear engine is also easily accessible, for example for maintenance or interchangeability operations including dismantling.

In a first preferred embodiment of the invention, said at least one arm consists of two arms having respective hooking parts connected to the rear engine, which hooking parts are diametrically opposite with respect to the longitudinal axis of the engine rear, the rear end of the cell being located between the arms.

Preferably, the two arms are shaped so that the two arms and the rear end of the cell delimit a concave space, with concavity oriented towards the rear, arranged in front of the rear motor.

Preferably, the two arms extend symmetrically on either side of a vertical median plane of the rear engine.

Preferably, the rear motor is connected to the two arms so that the rear motor can pivot about an axis orthogonal to the vertical median plane of the rear motor.

Preferably, the rear engine constitutes a pitch compensator.

Preferably, the cell has a rear part which has a thickness which is gradually reduced towards the rear up to the rear end of the cell.

In another preferred embodiment of the invention, said at least one arm consists of a single arm centered with respect to a vertical median plane of the rear engine.

Preferably, said single arm comprises a hooking part connected to an upper region of the rear motor.

Preferably, said single arm has a surface, disposed on the side of the longitudinal axis of the rear motor, which moves away from the longitudinal axis while approaching the rear motor.

In general, said at least one arm advantageously carries a vertical tail.

Furthermore, said at least one arm advantageously has a tapered shape towards the rear.

In preferred embodiments of the invention, the aircraft is an aircraft comprising a fuselage which said at least one arm extends rearward so that the arm keeps the rear engine offset behind and at a distance from one end central rear of the fuselage constituting said rear end of the airframe.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood, and other details, advantages and characteristics thereof will appear on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

- Figure 1 is a schematic perspective view of an aircraft according to a preferred embodiment of the invention;

- Figure 2 is an enlarged view of part of Figure 1;

- Figure 3 is a schematic top view of the aircraft of Figure 1;

- Figure 4 is an enlarged view of part of Figure 3;

- Figure 5 is a schematic side view of the aircraft of Figure 1;

- Figures 6-8 are schematic side views of a rear part of the aircraft of Figure 1, illustrating a rear engine thereof in three different positions.

- Figure 9 is a view similar to Figure 1, illustrating an aircraft according to another preferred embodiment of the invention;

- Figure 10 is a view similar to Figure 2, illustrating an aircraft according to another preferred embodiment of the invention;

- Figure 11 is a view similar to Figure 1, illustrating an aircraft according to another preferred embodiment of the invention;

FIG. 12 is a schematic side view of a rear portion of the aircraft in FIG. 11.

Throughout these figures, identical references can designate identical or analogous elements.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention is applicable to different types of aircraft, in particular to conventional airplanes, but also to airplanes of the type known as “with integrated fuselage” or “Blended Wing Body” according to the English terminology, or even to flying wings, that is to say aircraft whose airframe is entirely made up of the airfoil.

The aircraft 10 according to a first preferred embodiment of the invention, described with reference to Figures 1-8, is an aircraft of conventional type, that is to say an aircraft whose cell 12 comprises a fuselage 14 housing in particular the cockpit and passenger cabin, and two wings 16 respectively connected to two lateral parts of the fuselage 14. In a conventional manner, the cell 12 is generally symmetrical in shape with respect to a vertical median plane P of this cell, which constitutes a longitudinal plane of symmetry of the cell. The vertical orientation of this median plane refers to the orientation of the aircraft when it is parked on horizontal ground.

In this regard, it is indicated that by convention, the direction X corresponds to the longitudinal direction of the aircraft 10, which corresponds to the direction of advance thereof. On the other hand, the direction Y corresponds to the direction oriented transversely relative to the aircraft, while the direction Z corresponds to the vertical direction or the height of the aircraft. These three directions X, Y and Z are orthogonal to each other and form a direct trihedron.

As an indication, the wings 16 carry at least two front motors 18 symmetrical to each other with respect to the median vertical plane P, and the wings 16 are equipped with conventional mobile surfaces (not visible in the figures). The airframe 12 of the aircraft further comprises two horizontal stabilizers 20 on either side of the vertical median plane P and a vertical stabilizer 22 centered in the vertical plane P.

According to a feature of the invention, the cell 12 is extended by at least one arm 30A, 30B which carries a rear motor 34 and keeps it offset behind and at a distance D (FIG. 4) from a rear end 32 of the cell 12 defined on a longitudinal axis 37 of the rear engine (this axis being conventionally defined as being the axis of rotation of the engine rotor (s)).

The rear motor 34 is therefore arranged facing the rear end 32 of the cell 12 defined on the axis of the rear motor, and is thus able to ingest at least part of the air from the circulating boundary layer 36 along cell 12 (Figures 1, 2, 4, 5), in a substantially axisymmetric manner. This results in a reduction in the overall drag of the aircraft.

It is in particular remarkable that the support of the rear engine 34 in such a position, by means of one or more arms extending the aircraft cell, makes it possible to prevent the air intake 34A from the rear engine from being partially obstructed by the aircraft cell as in known semi-buried engines.

The rear motor 34 is also easily accessible, for example for maintenance and interchangeability operations.

In the first preferred embodiment of the invention, the arms are two in number and have respective hooking parts 35A, 35B which are connected to the rear motor 34 and which are diametrically opposite with respect to the longitudinal axis 37 rear engine. The rear motor 34 thus extends between the arms 30A,

30B.

In the illustrated embodiment, the aircraft 10 is an airplane, and the rear end 32 of the airframe 12 located between the arms 30A, 30B constitutes a central rear end 38 of the fuselage 14.

The rear motor 34 is thus centered relative to the vertical vertical plane P of the cell 12.

The position of the rear motor 34 facing the central rear end 38 of the fuselage 14 allows the ingestion of a major part of the air of the abovementioned boundary layer 36 by the rear motor 34.

In fact, receiving all of the air circulating inside the boundary layer 36 over the entire periphery of the fuselage, including therefore on the upper and lower parts of the fuselage, makes it possible to have a greater amount of the limit layer absorbed by the engine, in comparison with a known type of installation integrated in a lateral part of the fuselage.

In the first preferred embodiment of the invention, the arms 30A, 30B are lateral arms which extend symmetrically on either side of a vertical median plane V of the rear motor 34. In the example illustrated, this median vertical plane V of the rear motor merges with the median vertical plane P of the cell 12, the rear motor 34 being centered relative to the median vertical plane P of the cell 12.

It should be noted that the arms 30A, 30B extend generally parallel to a horizontal plane XY so that the rear motor 34 is offset behind the cell 12, and not offset up or down with respect to to the fuselage. As a variant, the arms 30A, 30B can be oriented slightly upwards or downwards.

Furthermore, the cell 12 (in this case the fuselage 14) has a rear part 40 having a vertical extent or thickness H which is gradually reduced in the direction of the rear to the rear end 32 (FIG. 5). It should be noted that the arms 30A, 30B extend in projection from the rear part 40.

The shape of the rear part 40 thus makes it possible to optimally guide the air from the boundary layer 36, circulating above and below the fuselage 14, towards the air intake of the rear engine 34.

In the illustrated embodiment, the horizontal stabilizers 20 and the vertical stabilizer 22 are connected to the rear part 40. The vertical stabilizer 22 thus extends in front of the rear engine 34.

In addition, the arms 30A, 30B have an arcuate shape so that each of the arms 30A, 30B follows the shape of a corresponding side of a nacelle 42 in which the rear motor 34 is housed. The connection of each arm 30A, 30B to nacelle 42 forms aerodynamic continuity.

In the example illustrated, each of the arms 30A, 30B extends rearward to a rear end of the nacelle 42.

In addition, each of the two arms 30A, 30B has a tapered shape towards the rear. In the example illustrated, the thicknesses of each arm 30A, 30B respectively in the direction Y and in the direction Z are thus reduced from front to rear along the direction X, as it appears in FIGS. 4 to 8 in particular.

The tapered shape of the arms 30A, 30B makes it possible to reduce the mass of the arms and the drag as well as possible while optimizing the load that these arms can support. This shape allows in particular a reduction of the wet surface.

As shown more particularly in FIG. 4, the shape of the two arms 30A, 30B is such that the arms 30A, 30B and the rear end 32 of the cell 12 delimit a concave space 44, with concavity oriented towards the rear, arranged in front of the rear engine 34. In the example illustrated, the concave shape of the concave space 44 can be seen in a top view of the aircraft.

In preferred embodiments of the invention, such as the embodiment illustrated in the figures, the rear motor 34 is connected to the two arms 30A, 30B so that the rear motor can pivot around an axis 46 orthogonal to the vertical median plane V of the rear engine, such an axis 46 therefore being parallel to the direction Y (FIGS. 1, 2 and 4).

FIGS. 6-8 thus illustrate the rear motor 34 in three different positions, namely a position in which the rear motor is tilted slightly around the axis 46 so as to orient its thrust slightly upwards (FIG. 6), neutral position in which the longitudinal axis 37 of the rear engine is parallel to the longitudinal direction X of the aircraft (FIG. 7), and a position in which the rear motor is tilted slightly around the axis 46 so as to orient its slightly pushed down (Figure 8). Note that the horizontal stabilizers 20 and the vertical stabilizer 22 are not visible in Figures 6-8 for clarity.

The pivot connection of the rear motor 34 to the arms 30A, 30B can be achieved by means of conventional devices which will not be described here.

Of course, in the case where the rear motor 34 is pivotally mounted, the rear end 32 of the cell 12 is defined on the longitudinal axis 37 of the motor when the motor is in its neutral position.

The pivoting ability of the rear motor 34 can in particular be taken advantage of by using the rear motor 34 as a pitch compensator. It should be understood by this that the piloting system of the aircraft controls a pivoting movement of the rear engine 34 when an order to modify the pitch compensation setting is given from the control station of the aircraft. This characteristic makes it possible in particular to prevent the horizontal tail units 20 from having to fulfill this function. These horizontal stabilizers 20 can thus be entirely made up respectively of two elevators of relatively small dimensions and of high elongation. This results in a reduction in the drag induced by the horizontal stabilizers 20.

FIG. 9 illustrates an alternative embodiment in which the vertical stabilizer 22 of FIGS. 1-5 is replaced by a pair of vertical stabilizers 22A, 22B carried respectively by the arms 30A, 30B. The vertical tail units 22A, 22B are thus spaced laterally relative to the rear engine 34 and therefore relative to the air flow supplying the rear engine. Such a configuration thus makes it possible in particular to prevent the boundary layer 36 supplying the rear engine from being disturbed by a vertical tail before entering the rear engine. The ingestion of the boundary layer 36 by the rear motor is therefore improved.

FIG. 10 illustrates another alternative embodiment in which the horizontal stabilizers 20 are integrated into the arms 30A, 30B, for example by being formed respectively from movable planes arranged at the rear end of the arms 30A, 30B.

In the embodiment of the invention described above, the arms 30A, 30B are lateral arms. However, other configurations of the arms are possible without departing from the scope of the invention.

For example, the arms 30A, 30B can be in a configuration turned 90 degrees relative to that of the embodiment described above. The arms are in this case respectively in a high position and in a low position. The shape of the rear part 40 of the fuselage is then preferably adapted so that this rear part 40 has a transverse extent (in the direction Y) which gradually decreases towards the rear up to the rear end 32 of the cell. In addition, the concavity of the concave space 44 is in this case observable in a side view of the aircraft (in direction Y).

In this case, the rear part 40 advantageously has a lateral extent which gradually reduces in the direction of the rear to the rear end 32, in a manner similar to that described above.

The pivoting ability of the motor described above can be transposed to embodiments of this type, in which case the pivoting takes place around a vertical axis. In some of these embodiments, the rear motor can thus constitute a yaw compensator.

In other embodiments, the number of arms can be greater than two.

In another preferred embodiment of the invention illustrated in Figures 11 and 12, the rear motor 34 is carried by a single arm 30C. This single arm is centered along the vertical median plane P of the aircraft.

The single arm 30C has a surface 48, disposed on the side of the longitudinal axis 37 of the rear motor 34, which moves away from this longitudinal axis 37 while approaching the motor.

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In the example illustrated, the single arm 30C has a hooking portion 35C connected to an upper region of the rear motor, so that the surface 48 is a lower surface of the single arm 30C.

In addition, in the example illustrated, the single arm 30C carries a vertical tail 22, which is for example integrated into the attachment portion 35C.

Generally, the rear engine 34 can be a conventional turbojet, or an electric motor. In the first case, the rear engine 34 can in particular fulfill the function of auxiliary power group ("APU") participating or not in the propulsion of the aircraft. In the second case, the electrical energy supplying the rear motor can be supplied by a battery or by one or more generators driven by the front motors 18.

The rear motor 34 may also include a thrust reversal device and allow the use of front motors without such a device. In the case where the rear motor 34 is an electric motor, the latter may in particular comprise a fan with variable setting capable of adopting a reverse thrust setting.

The embodiments described above relate to a central rear engine of an aircraft. Those skilled in the art will understand that the mode of arrangement and engine support proposed by the invention is also applicable to an engine supported by an aircraft wing (in particular in combination with one or more other similar rear engines), to which if the arms extend the wing. Similarly, the invention is applicable to an aircraft with integrated fuselage and to a flying wing, in which case the rear engine can also be in the central position, or be offset laterally relative to the vertical median plane of the flying wing (in particular in combination with one or more other similar rear engines).

Claims (13)

1. Aircraft (10), comprising a cell (12) and at least one rear engine (34), characterized in that the cell (12) is extended by at least one arm (30A, 30B; 30C) which carries the engine rear (34) and keeps it offset back and away from a rear end (32) of the cell (12) defined on a longitudinal axis (37) of the rear motor (34). 2. Aircraft according to claim 1, wherein said at least one arm consists of two arms (30A, 30B) having respective hooking parts (35A, 35B) connected to the rear engine (34), which hooking parts are diametrically opposite with respect to the longitudinal axis (37) of the rear motor, the rear end (32) of the cell (12) being located between the arms (30A, 30B). 3. Aircraft according to claim 2, in which the two arms (30A, 30B) are shaped so that the two arms (30A, 30B) and the rear end (32) of the airframe define a concave space (44), with concavity oriented towards the rear, arranged in front of the rear motor (34). 4. Aircraft according to claim 2 or 3, in which the two arms (30A, 30B) extend symmetrically on either side of a vertical median plane (V) of the rear engine (34). 5. Aircraft according to claim 4, in which the rear motor (34) is connected to the two arms (30A, 30B) so that the rear motor can pivot around an axis (46) orthogonal to the vertical vertical plane (V) of the rear engine. 6. Aircraft according to claim 5, in which the rear engine (34) constitutes a pitch compensator. 7. Aircraft according to any one of claims 4 to 6, in which the airframe (12) has a rear part (40) which has a thickness (H) which is gradually reduced towards the rear up to the rear end (32) of the cell (12). 8. Aircraft according to claim 1, wherein said at least one arm consists of a single arm (30C) centered with respect to a vertical median plane (V) of the rear engine (34). 9. Aircraft according to claim 8, in which said single arm (30C) comprises a hooking part (35C) connected to an upper region of the rear engine (34). 10. Aircraft according to claim 8 or 9, wherein said single arm (30C) has a surface, disposed on the side of the longitudinal axis (37) of the rear engine (34), which moves away from the longitudinal axis ( 37) when approaching the rear motor (34). 11. Aircraft according to any one of claims 1 to 10, wherein said at least one arm (30A, 30B; 30C) carries a vertical tail (22A, 22B; 22). 12. Aircraft according to any one of claims 1 to 11, wherein said at least one arm (30A, 30B; 30C) has a tapered shape towards the rear. 13. Aircraft according to any one of claims 1 to 12, the aircraft being an airplane comprising a fuselage (14) which said at least one arm (30A, 30B; 30C) extends rearwards so that the arm ( 30A, 30B; 30C) keeps the rear motor (34) offset behind and at a distance from a central rear end (38) of the fuselage constituting said rear end (32) of the airframe (12). S.60803