RU2785230C1 - Aircraft and method for its manufacture - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: invention relates to the field of aviation, in particular to aircraft structures. The aircraft (1) contains a fuselage (2) with a first longitudinal axis (A) and a tail section (14) located at the tail end (13) of the fuselage (2). The tail section (14) contains two surfaces (15a, 15b) arranged in a V-shape, inclined towards each other and symmetrical about the first axis (A); each surface (15a, 15b) contains an associated winglet (19a, 19b) transverse to the surface (15a, 15b) and stationary relative to the surface (15a, 15b).

EFFECT: invention makes it possible to improve the longitudinal and lateral stability of the aircraft in a variable way without changing the transverse angle V and the size of the control surfaces.

6 cl, 13 dwg

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the priority of European Patent Application No. 18214252.1, filed December 19, 2018, the entire disclosure of which is hereby incorporated by reference.

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to an aircraft and a corresponding method for manufacturing said aircraft.

In particular, the aircraft is an airplane, tiltrotor, gyrodine or gyroplane.

BACKGROUND OF THE INVENTION

The aircraft includes, in a known manner, a fuselage extending along the first longitudinal axis of the roll, two cantilever wings protruding from the fuselage, and a tail keel protruding in a cantilever manner from the tail end of the fuselage along a plane containing the first longitudinal axis and located vertically when the aircraft is located on the ground.

It is also possible to identify a coordinate system centered at the center of mass of the aircraft and containing, in addition to the first roll axis:

- a second pitch axis which is perpendicular to the first roll axis and extends parallel to the line joining the wingtips; and

- a third yaw axis which is perpendicular to the aforementioned first and second axes.

In a known manner, the tail keel comprises a rotary rudder which is movable to control the yaw of the aircraft.

In the solution described above, a known type of aircraft comprises a tail located in the tail section.

The tail assembly is also located at the tail end of the fuselage, extending from both sides of the fuselage in a cantilever manner and lying on a horizontal plane when the aircraft is on the ground.

In a known manner, the tail includes two fixed surfaces, known as stabilizers, to which corresponding movable surfaces, known as elevators, are pivotally attached.

In a way known in flight mechanics, it is possible to determine:

- angle of attack of the aircraft, equal to the angle formed between the first roll axis and the projection of the velocity vector on the plane formed by the first roll axis and the third yaw axis; and

- aircraft side slip angle equal to the angle formed between the velocity vector and the plane formed by the first roll axis and the third yaw axis.

A change in the angle of attack and/or side slip angle of the aircraft causes a corresponding change in the pitch angle of the wings and tail assembly, followed by a change in the generated lift forces.

In addition, it is possible to define the stability of an aircraft as the ability to autonomously return to its previous spatial position after the effect of a small disturbance, such as a gust of wind, on the aircraft, for example, ceases.

More specifically, if the aforementioned small perturbation causes a rotation about the second pitch axis and therefore a change in the so-called angle of attack of the aircraft, the aforementioned ability is called longitudinal static stability.

On the other hand, the ability to autonomously return to the previous spatial position after changing the side slip angle is called lateral stability.

An example of a small perturbation that causes a change in side slip angle is a perturbation that causes the aircraft to rotate about the first roll axis. Under these circumstances, rotation about the roll axis creates an unbalanced weight component parallel to the second pitch axis. This component causes the aircraft to side-slip parallel to the second pitch axis and in the direction of the underlying wing, with a subsequent change in the so-called side-slip angle of the aircraft.

The stabilizers create appropriate lift forces that guarantee the longitudinal static stability of the aircraft. On the other hand, the elevators are movable relative to the associated stabilizers to control the pitch movement of the aircraft around the second axis.

Meanwhile, lateral stability is guaranteed by the keel, and can be further increased by having wings with a positive lateral angle V inclined relative to each other to form a slightly inclined V-shape with the apex on the fuselage, with reference to the mode in which the aircraft is on the ground.

In fact, the above-described side-slip movement causes an airflow transverse to the aircraft, which will merge with the flow due to the horizontal flight of the aircraft. As a result of the tilt between the wings due to the (positive) transverse angle V, the resulting current that strikes the underlying wing has a larger angle of attack than the angle of attack of the opposite surface. Therefore, the lift developed by the lowered wing is greater than the lift developed by the other wing, which induces a moment along the first roll axis that tends to return the aircraft to undisturbed attitude.

According to a further known type of design solution, the tailfin and tailplane are replaced by two control surfaces projecting from the tail end symmetrically to the first longitudinal axis of the fuselage and lying on respective planes inclined to the first axis so as to adopt a V-shaped configuration commonly known in the industry. as a "V-tail".

The angle formed by each plane on which the control surface lies with the plane formed by the first roll axis and the second pitch axis is called the roll angle V.

This design decision has been implemented in Beech Bonanza, Fouga Magister, Predator, Eclipse 400 and Cirrus jet aircraft, for example.

V-tail aircraft are of interest because, compared to conventional aircraft, they have fewer components and parts, less aerodynamic drag as a result of less tail interference with the fuselage wake, and less exposure to air currents deflected downward by the wings.

With reference to the aircraft's level flight mode, the control surfaces generate respective lift forces, each of which has a first horizontal component parallel to the second pitch axis and a second vertical component parallel to the third yaw axis.

The second vertical components give a certain level of longitudinal stability of the aircraft, i.e. in terms of the aircraft's ability to autonomously return to a stable attitude when a gust of wind causes the aircraft to rotate about the second pitch axis.

The lift forces generated by the control surfaces give a certain level of lateral stability to the aircraft.

This is due to the fact that the surfaces of the tail section behave like two wings with a positive transverse V angle.

More specifically, due to the small perturbation that causes the roll moment, the aircraft experiences side slip towards the lowered control surface.

Therefore, the lift developed by the lowered surface is greater than the lift developed by the other surface, which induces a moment along the first roll axis that tends to return the aircraft to undisturbed attitude.

For a given cruising speed, the levels of longitudinal and lateral stability that the control surfaces give are uniquely determined by the area of the control surfaces and the positive lateral angle V.

These characteristics are usually determined at the preliminary design stage.

The industry recognizes the need to be able to increase the pitch and roll characteristics of an aircraft in a variable manner at will and independently of each other without changing the lateral V angle and the size of the control surfaces.

The industry also recognizes the need to be able to change the roll and roll characteristics of an aircraft independently of each other and at a stage following the preliminary design stage.

EP-A-3296202 and US 4,691,878 illustrate the use of endplates, commonly known as "winglets", in an aircraft.

In particular, these winglets are located at the free ends of the respective wings and make it possible to reduce the inductive drag caused by the vortices at the tips. In this way, the winglets increase the efficiency of the wings without the need for an effective extension of the wings.

EP-A-1568604 and US-B-5,211,538 illustrate the use of winglets on respective risers of a helicopter's horizontal tail.

DE-U-202014003490 discloses an aircraft according to the preamble of paragraph 1 of the claims and a method for manufacturing an aircraft according to the preamble of paragraph 6 of the claims.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an aircraft that can satisfy the above needs in a simple and inexpensive manner.

The above problem is solved with the help of the present invention in terms of aircraft, according to paragraph 1 of the claims.

The present invention also relates to a method for manufacturing an aircraft according to claim 6 of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, three preferred embodiments of the invention are described below solely by way of non-limiting example and with reference to the accompanying drawings, in which:

- Figure 1a is a front view of a first embodiment of an aircraft, in particular a tiltrotor, manufactured according to the principles of the present invention;

- Figure 1b is a front view of certain parts of a tiltrotor according to the second embodiment of the present invention;

- Figure 1c is a front view of certain parts of a tiltrotor according to a third embodiment of the present invention;

- Figures 2 and 3 schematically show the areas of high pressure and low pressure and the aerodynamic forces generated on the V-shaped tail section of each of the first, second and third versions of the tiltrotor in the event of an increase in the angle of attack of the aircraft and in the case of an increase in the angle of side slip of the aircraft respectively;

- Figures 4 and 5 schematically show the areas of high pressure and low pressure and the aerodynamic forces generated on the V-tail and winglets of the second embodiment of the tiltrotor in Figure 1b in the case of an increase in the angle of attack of the aircraft and in the case of an increase in the angle of side slip of the aircraft, respectively ;

- Figures 6 and 7 schematically show the areas of high pressure and low pressure and the aerodynamic forces generated on the V-shaped tail section and winglets of the third embodiment of the tiltrotor in Figure 1c in the case of an increase in the angle of attack of the aircraft and in the case of an increase in the angle of side slip of the aircraft respectively;

- Figures 8 and 9 schematically show the areas of high pressure and low pressure and aerodynamic forces generated on the V-shaped tail section and winglets of the first variant of the tiltrotor in Figure 1a in the case of an increase in the angle of attack of the aircraft and in the case of an increase in the angle of side slip of the aircraft, respectively ;

- Figure 10 is a perspective view of the tail section of the first embodiment of the tiltrotor in Figure 1a;

- Figure 11 is a perspective view of the tail section of the second embodiment of the tiltrotor in Figure 1b;

- Figure 12 is a perspective view of the tail section of the third embodiment of the tiltrotor in Figure 1c; and

- Figure 13 is a perspective view of the first embodiment of the tiltrotor in Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1a, reference numeral 1 denotes an aircraft, in particular a tiltrotor, manufactured according to the first embodiment of the invention.

Tiltrotor 1 basically contains:

- fuselage 2 having an axis A of longitudinal extent;

- two cantilever wings 3 protruding from the respective mutually opposite sides of the fuselage 2 and transverse to axis A; and

- two gondolas 4 containing the corresponding propellers 5.

The fuselage 2, in turn, includes a forward end 12 and an aft end 13 opposite each other along axis A.

Gondolas 4 tilt in one piece with screws 5 around axis C relative to wings 3.

Axis C is transverse to axis A and axes B.

Tiltrotor 1 can be selectively located:

- in the configuration "helicopter" (Figure 1a), in which the axes B of the screws 5 are perpendicular to the axis A and axis C; and

- in the "airplane" configuration (Figure 13), in which the axes B of the screws 5 are parallel to the axis A and perpendicular to the axis C.

With reference to Figure 13, it is possible to define a coordinate system having its origin at the center of mass of tiltrotor 1 and formed by:

- roll axis A, around which tiltrotor 1 rolls during roll movement;

a pitch axis E which is perpendicular to the roll axis A and extends parallel to the line joining the wingtips 3; and

- the yaw axis F, which is perpendicular to the axes A and E mentioned above.

Below in this description, the moments acting on the tiltrotor 1 and directed around the axes A, E and F are identified as "roll moment", "pitch moment" and "yaw moment", respectively.

Axes A, E and F are commonly known as "master axes".

With reference to Figure 13, in each flight mode, it is possible to determine the angle of attack α of the tiltrotor 1, defined as the angle between:

- orthogonal projection of the velocity vector V onto the midplane of tiltrotor 1 formed by axes A and F; and

- axis A.

In any flight mode, it is also possible to determine the side slip angle β of the tiltrotor 1, defined as the angle between:

- velocity vector V; and

- the median plane of tiltrotor 1, formed by axes A and F.

A change in the angle of attack α and/or the side slip angle β of the tiltrotor 1 causes a corresponding change in the pitch angle of the wings 3.

In addition, it is possible to define the stability of tiltrotor 1 as the ability to autonomously return to the previous spatial position as soon as the impact of a small temporary disturbance, such as a gust of wind, for example, on tiltrotor 1 stops.

More specifically, if the aforementioned small perturbation causes a "pitch moment" and therefore a rotation about the pitch axis E, the aforementioned ability is called longitudinal static stability. It is important to note that the aforementioned "pitch moment" also causes an increase in the angle of attack α of the tiltrotor 1.

On the other hand, the ability to return to the previous spatial position after changing the side slip angle β is called lateral stability.

For example, a change in side slip angle β occurs each time a disturbance causes a roll moment around the roll axis A.

With reference to Figures 1a, 8, 9, 10 and 13, tiltrotor 1 further comprises a tail section 14 located at the tail end 13 of the fuselage 2.

This tail portion 14 comprises two surfaces 15a and 15b arranged symmetrically about axis A and forming a V-shape.

Starting from the fuselage 2, the surfaces 15a and 15b diverge from each other.

In the case shown, the surfaces 15a and 15b diverge from each other on the side of the fuselage 2 where the propellers 5 are located when the tiltrotor 1 is in the helicopter configuration.

Surfaces 15a and 15b have respective end edges 16a and 16b opposite the fuselage 2.

Surfaces 15a and 15b form respective surfaces 17a and 17b facing each other and located on the axis A side, and corresponding surfaces 18a and 18b opposite to respective surfaces 17a and 17b.

Due to the horizontal movement of the tiltrotor 1, the surfaces 15a and 15b generate corresponding lift forces perpendicular to the median planes on which the surfaces 15a and 15b lie.

Each surface 15a and 15b includes a respective winglet 19a and 19b transverse to the bonded surface 15a and 15b and fixed relative to the bonded surface 15a and 15b.

In more detail, the winglets 19a and 19b extend symmetrically about the median plane of the fuselage 2 formed by axes A and F.

Preferably, winglets 19a and 19b are planar.

In the first embodiment of the tiltrotor 1, shown in Figures 1a and 10, each winglet 19a and 19b contains:

a respective section 20a and 20b which extends from the respective edge 16a and 16b on the side of the respective surface 17a and 17b; and

a respective section 21a and 21b which extends from the respective edge 16a and 16b on the side of the respective surface 18a and 18b.

Sections 20a and 20b contain:

- respective surfaces 25a and 25b adjacent to respective surfaces 17a and 17b of surfaces 15a and 15b; and

- respective surfaces 26a and 26b opposite the respective surfaces 25a and 25b.

Sections 21a and 21b contain:

- respective surfaces 27a and 27b adjacent to respective surfaces 18a and 18b, and

- respective surfaces 28a and 28b opposite the respective surfaces 27a and 27b.

In the case shown, the winglets 19a and 19b and the associated surfaces 15a and 15b form respective angles at the edges 16a and 16b in the range between 80 and 100 degrees, preferably 90 degrees.

It is important to note that the aforementioned angles are the angles between the planes tangent to the winglets 19a and 19b and the associated surfaces 15a and 15b at the respective edges 16a and 16b.

In addition, the winglets 19a and 19b are parallel to the opposite surfaces 15b and 15a.

In the case shown, the median planes on which the surfaces 15a and 15b lie are inclined at 90 degrees to each other and have a larger area than the corresponding winglets 19a and 19b.

With reference to Figures 1b, 4, 5 and 11, reference numeral 1' denotes a tiltrotor according to a further embodiment of the present invention.

Tiltrotor 1' is similar to tiltrotor 1 and will be described below only with respect to the differences; where possible, the same or corresponding parts of convertiplanes 1 and 1' will be identified by the same reference numerals.

In particular, tiltrotor 1' differs from tiltrotor 1 in that the winglets 19a and 19b extend from the edges 16a and 16b only on the side of the respective surfaces 18a and 18b.

In other words, each winglet 19a or 19b extends from the edge 16a or 16b of the corresponding surface 15a or 15b on the side facing away from the edge 16b or 16a of the other surface 15b or 15a.

More specifically, winglets 19a and 19b contain only sections 21a and 21b.

With reference to Figures 1c, 6, 7 and 12, reference numeral 1” denotes a tiltrotor according to a further embodiment of the present invention.

Tiltrotor 1” is similar to Tiltrotor 1 and will be described below only with respect to the differences; where possible, the same or corresponding parts of convertiplanes 1 and 1" will be identified by the same reference numerals.

In particular, tiltrotor 1" differs from tiltrotor 1 in that the winglets 19a and 19b extend from the edges 16a and 16b only on the side of the respective surfaces 17a and 17b.

In other words, each winglet 19a or 19b extends from the edge 16a or 16b of the corresponding surface 15a or 15b on the side facing towards the edge 16b or 16a of the other surface 15b or 15a.

More specifically, winglets 19a and 19b contain only sections 20a and 20b.

In use, the tiltrotor 1 takes off and lands in a helicopter configuration and moves in level flight at high speeds and altitudes in an airplane configuration.

Tiltrotor 1 can be selectively located:

- in the configuration "helicopter" (Figure 1a), in which the axes B of the screws 5 are perpendicular to the axis A and axis C; and

- in the "airplane" configuration (Figure 13), in which the axes B of the screws 5 are parallel to the axis A and perpendicular to the axis C.

With reference to the "airplane" configuration of the surfaces 15a and 15b of the tail section 14 and the winglets 19a and 19b give the desired level of longitudinal static stability and lateral stability.

It is important to emphasize that surfaces 15a and 15b and winglets 19a and 19b are shown flat in Figures 4-9 for simplicity only.

In reality, surfaces 15a and 15b and winglets 19a and 19b have wing profiles with a high pressure surface (indicated by "+") and a low pressure surface (indicated by "-"). These wing profiles produce lift in a known manner from the low pressure surface to the high pressure surface.

It is important to emphasize that if high pressure regions (indicated by "+") and therefore low pressure regions (indicated by "-") of surfaces 15a and 15b and winglets 19a and 19b are adjacent to each other, constructive interference is created between these regions. high pressure/low pressure (Figures 4 and 7). This constructive interference essentially does not change the values of the forces N1, N2; G1, G2, G; L1, L2; M1, M2; H1, H2; I1, I2 generated by surfaces 15a and 15b and winglets 19a and 19b.

Conversely, if each high pressure region (indicated by "+" sign) of surfaces 15a and 15b and winglets 19a and 19b is adjacent to a corresponding low pressure region (indicated by "-"), destructive interference is created between these high pressure regions and the corresponding low pressure regions. pressure adjacent to them (Figures 5 and 6). This destructive interference reduces the values of the forces G1, G2; N1, N2 created by surfaces 15a and 15b.

It is also important to emphasize that in Figures 4-9 the conditions of high pressure and low pressure, as well as the forces N1, N2, N; G1, G2, G; L1, L2, L; M1, M2, M; H1, H2, H; I1, I2, I, must be considered as additional high pressures/low pressures and forces in relation to the pressure and force values acting on surfaces 15a and 15b and winglets 19a and 19b when tiltrotor 1, 1', 1” is in undisturbed modes flight.

The operation of the surfaces 15a and 15b will be described below starting from the state in which the tiltrotor is in level flight mode with zero angle of attack α and zero side slip angle β.

With reference to Figures 2 and 3 only the surfaces 15a and 15b are shown in operation without the use of winglets 19a and 19b.

More specifically, with reference to Figure 2, in the case where the disturbance causes an increase in the angle of attack α of the tiltrotor 1, 1', 1”, i.e. lifting the nose 12 of the tiltrotor 1, 1', 1" relative to the tail section 14, the surfaces 18a and 18b are subjected to high pressure, while the surfaces 17a and 17b are subjected to low pressure.

This is due to the fact that the increase in the angle of attack α tiltrotor 1, 1', 1" causes a similar increase in the pitch angle of the surfaces 15a and 15b.

In this regard, the surfaces 15a and 15b develop lift forces N1 and N2 directed from the surfaces 17a and 17b to the surfaces 18a and 18b. The resulting N forces N1 and N2 are essentially parallel to the axis F and are applied to the surfaces 15a and 15b. This resulting N creates a corrective moment about the pitch axis E, which returns the tiltrotor 1 to the level flight mode.

With reference to Figure 3, in the case where the disturbance causes an increase in the side slip angle β of the tiltrotor 1, 1', 1”, this leads to a change in the pitch angle of the surfaces 15a and 15b.

This change causes:

- high pressure on the surface 17a and low pressure on the surface 18a, as for the surface 15a; and

- high pressure on surfaces 18b and low pressure on surfaces 17b, as for surface 15b.

It follows that surface 15a generates lift G1 from surface 17a to surface 18a and surface 15b generates lift G2 from surface 18b to surface 17b.

The resultant lift forces G1 and G2 is a force G parallel to the axis E and creates a yaw moment about the axis F on the tiltrotor 1, which reduces the side slip angle β and returns the tiltrotor 1, 1', 1” to an undisturbed flight mode with an essentially zero angle β side slip.

With reference to Figures 4 and 5, the operation of the tail section 14 of the tiltrotor 1' according to the second embodiment of the invention is shown.

According to this embodiment, the winglets 19a and 19b contain only the respective sections 21a and 21b.

More specifically, with reference to Figure 4, in the case where the disturbance causes an increase in the angle of attack α of the tiltrotor 1', i. e. lifting the nose 12 of the tiltrotor 1' relative to the tail section 14, the surfaces 27a and 27b are subjected to high pressure, while the surfaces 28a and 28b are subjected to low pressure.

In this way, constructive interference is created between the high pressure and low pressure regions, affecting the surfaces 15a and 15b and the sections 21a and 21b of the winglets 19a and 19b.

These high pressures and low pressures result from the increase in the pitch angle of the winglets 19a and 19b resulting from the increase in the angle of attack α of the tiltrotor 1'.

Therefore, in addition to the forces N1 and N2 generated by the surfaces 15a and 15b (Figure 2), the tail section 14 also develops the forces L1 and L2 generated by the winglets 19a and 19b. These forces L1 and L2 have a net L substantially parallel to the axis F, which is directed in the same direction as the net N of forces N1 and N2 and sums with it. This increase in the net N+L applied to the tail section 14 increases the corrective moment about the pitch axis E, which returns the tiltrotor 1' to level flight.

In other words, the presence of winglets 19a and 19b increases the level of longitudinal stability of the tiltrotor 1'.

With reference to Figure 5, in the case where the disturbance causes an increase in the side slip angle β of the tiltrotor, this results in a change in the pitch angle of the surfaces 15a and 15b and the winglets 19a and 19b.

In addition to what is shown in Figure 3, this change causes:

- high pressure on the surface 27a and low pressure on the surface 28a, as for the winglet 19a; and

- high pressure on surfaces 28b and low pressure on surfaces 27b, as far as winglet 19b is concerned.

It follows that winglet 19a generates lift M1 from surface 27a to surface 28a and winglet 19b generates lift M2 from surface 28b to surface 27b.

Thus, destructive interference is created between the high pressure areas and the low pressure areas, affecting surfaces 15a and 15b and sections 21a and 21b of winglets 19a and 19b. This causes the forces G1 and G2 to decrease compared to the state in Figure 2.

The resultant lift forces M1 and M2 is a force M parallel to the axis E, which is added to the reduced resultant G of the forces G1 and G2 and creates a yaw moment about the axis F on the tiltrotor 1', which reduces the side slip angle β and returns the tiltrotor 1' to the mode unperturbed flight with essentially zero side slip angle β.

Since the forces G1 and G2 are reduced compared to the state in Figure 2 due to the aforementioned destructive interference, the presence of the winglets 19a and 19b does not substantially change the level of lateral stability of the tiltrotor 1'.

In other words, the resulting G+M in the configuration in Figure 5 is essentially equal to the resulting G in the configuration in Figure 3.

With reference to Figures 6 and 7 shows the operation of the tail section 14 tiltrotor 1" according to the third embodiment of the invention.

According to this embodiment, the winglets 19a and 19b contain only the respective sections 20a and 20b.

More specifically, with reference to Figure 6, in the case where the disturbance causes the tiltrotor 1's angle of attack α to increase, lifting the nose 12 of the tiltrotor 1″ relative to the tail 14, the surfaces 25a and 25b are subjected to high pressure, while the surfaces 26a and 26b are subjected to low pressure.

These high pressures and low pressures result from the increase in the pitch angle of the winglets 19a and 19b resulting from the increase in the angle of attack α of the tiltrotor 1".

Thus, destructive interference is created between the high pressure and low pressure areas, affecting surfaces 15a and 15b and sections 20a and 20b of winglets 19a and 19b. This causes the forces N1 and N2 to decrease compared to the state in Figure 2.

In addition, in addition to the forces N1 and N2 generated by the surfaces 15a and 15b (Figure 2), the tail section 14 also develops the forces H1 and H2 generated by the winglets 19a and 19b. These forces H1 and H2 have a net H substantially parallel to the axis F, which adds up to a reduced net N of the forces N1 and N2. This increase in the resultant applied to the tail section 14 increases the corrective moment about the pitch axis E, which returns the tiltrotor 1″ to the level flight mode.

Since the forces N1 and N2 are reduced compared to the state in Figure 2 due to the aforementioned destructive interference, the presence of the winglets 19a and 19b does not substantially change the level of longitudinal stability of the tiltrotor 1”.

In other words, the resulting N+H in the Figure 6 configuration is substantially equal to the resulting N in the Figure 2 configuration.

With reference to Figure 7, in the case where the disturbance causes an increase in the side slip angle β of the tiltrotor, this leads to a change in the pitch angle of the surfaces 15a and 15b and the winglets 19a and 19b.

In addition to what is shown in Figure 3, this change causes:

- high pressure on the surface 25a and low pressure on the surface 26a, as for the winglet 19a; and

- high pressure on surfaces 26b and low pressure on surfaces 25b as regards winglet 19b.

It follows that winglet 19a generates lift I1 from surface 25a to surface 26a and winglet 19b generates lift I2 from surface 26b to surface 25b.

The resultant lift forces I1 and I2 is a force I parallel to axis E. This resultant force I is an axis parallel force that adds up to the resultant G of forces G1 and G2 and creates a yaw moment about the F axis on a tiltrotor 1”, which reduces the angle β side slip and returns the tiltrotor 1″ to the undisturbed flight mode with essentially zero side slip angle β.

In other words, the presence of winglets 19a and 19b increases the level of lateral stability of tiltrotor 1”.

With reference to Figures 8 and 9 shows the operation of the tail section 14 tiltrotor 1 according to the first embodiment of the invention.

According to this embodiment, the winglets 19a and 19b comprise both respective sections 20a and 20b and respective sections 21a and 21b.

More specifically, with reference to Figure 8, in the case where the disturbance causes the angle of attack α of the tiltrotor 1 to increase, i. lifting the nose 12 of the tiltrotor 1 relative to the tail section 14, the previously described forces H1, H2, L1 and L2 are generated in addition to the forces N1 and N2 and in the same direction as the forces N1 and N2.

In this regard, a total resulting N+H+L is created, parallel to the F axis, with a subsequent additional increase in the stabilizing corrective moment around the pitch axis E, which returns the tiltrotor 1 to the level flight mode.

With reference to Figure 9, in the case where the disturbance causes the tiltrotor side slip angle β to increase, the previously described forces I1, I2, M1 and M2 are generated in addition to the forces G1 and G2.

This creates an overall result G+I+M parallel to the E axis, followed by an additional increase in the stabilizing yaw moment around the F axis on the tiltrotor 1, which reduces the side slip angle β and returns the tiltrotor 1 to an undisturbed flight mode with essentially zero angle β side slip.

From the study of the tiltrotor 1, 1', 1" and the method according to the present invention, the advantages that can be achieved with them are obvious.

In particular, the winglets 19a and 19b, made on the surfaces 15a and 15b of the tail section 14, make it possible to increase the longitudinal stability and lateral stability of the tiltrotor 1.

In other words, the winglets 19a and 19b allow the tiltrotor 1, 1', 1" to autonomously and stably return to its original spatial position in the event of disturbances due to gusts of wind, for example, which cause a change in the angle of attack α and side slip angle β of the tiltrotor 1.

This increase in longitudinal and lateral stability occurs in such a way that it can be modulated as desired, i.e. it is possible to obtain increases in the levels of longitudinal and transverse stability by values that are independent of each other and can be changed as desired.

It is important to emphasize that the increase in longitudinal and lateral stability has nothing to do with the reduction in induced drag, obtained in a known manner by the use of winglets at the tips of the respective wings.

In addition, the winglets 19a and 19b allow you to change the values of longitudinal and lateral stability, regardless of the lateral angle V and the length of the surfaces 15a and 15b of the tail section 14.

Thus, it is possible to set the dimensions of the surfaces 15a and 15b with a preliminary value of longitudinal and lateral stability at the preliminary design stage, and the size of the winglets 19a and 19b only at a later stage in cases where it becomes necessary to change this value.

Finally, since the winglets 19a and 19b are respectively parallel to the opposite surfaces 15b and 15a, the effect of negative aerodynamic interference between these winglets 19a and 19b and the surfaces 15b and 15a is reduced. This allows you to increase the overall value of the forces L1, L2; M1, M2; H1, H2; I1, I2, created by winglets 19a and 19b, with an obvious improvement in the longitudinal and lateral stability of the tiltrotor 1, 1’, 1”.

The above advantage is further enhanced when the angle between each winglet 19a or 19b and the associated surface 15a or 15b is equal to or close to 90 degrees.

Finally, it is clear that the modifications and variations of the tiltrotor 1, 1', 1" and the corresponding method of manufacture set forth herein can be made without deviating from the scope of protection defined in the claims.

In particular, instead of a tiltrotor, the aircraft may be a helicopter, an airplane or a gyrodine.

Claims (36)

1. Aircraft (1, 1’, 1”), including: - fuselage (2) with axis (A) of longitudinal extent; and - tail section (14) located at the tail end (13) of said fuselage (2); while the specified tail section (14) contains two surfaces (15a, 15b), located in a V-shape, inclined relative to each other and symmetrical about the specified first axis (A); wherein each said surface (15a, 15b) contains an associated winglet (19a, 19b) located transversely relative to the associated said surface (15a, 15b) and fixed relative to the associated said surface (15a, 15b); wherein said first and second surfaces (15a, 15b) comprise: - respective first surfaces (17a, 17b) facing each other; - respective second surfaces (18a, 18b) opposite the respective first surfaces (17a, 17b); and - respective end edges (16a, 16b) opposite said fuselage (2) from which the linked said winglets (19, 19b) continue; and each specified winglet (19a, 19b) contains: a corresponding first section (20a, 20b) extending in a cantilever manner from the associated end edge (16a, 16b) on the side of said corresponding first surface (17a, 17b); at the same time, starting from the associated specified end edge (16a, 16b), the specified first sections (20a, 20b) converge towards each other, characterized in that each specified winglet (19a, 19b) additionally contains a corresponding second section (21a, 21b) extending in a cantilever manner from the associated end edge (16a, 16b) from the side of said corresponding second surface (18a, 18b); wherein, starting from the associated said end edge (16a, 16b), said first portions (21a, 21b) diverge from each other. 2. Aircraft according to claim 1, characterized in that said winglets (19a, 19b) continue symmetrically with respect to the median plane of said fuselage (2). 3. Aircraft according to claim. 1 or 2, characterized in that each specified winglet (19a, 19b) forms an angle in the range between 80 and 100 degrees, preferably 90 degrees, with the corresponding specified surface (15a, 15b) at the corresponding specified end edge (16a, 16b). 4. An aircraft according to any one of the preceding claims, characterized in that the median plane of each said winglet (19a, 19b) is parallel to the median plane of said surface (15b, 15a) from which another said winglet (19b, 19a) continues. 5. An aircraft according to any of the preceding paragraphs, characterized in that it is a tiltrotor. 6. A method for manufacturing an aircraft (1), characterized in that it includes the steps in which: i) make the fuselage (2) with the axis (A) of the longitudinal extent; ii) positioning two mutually inclined surfaces (15a, 15b) symmetrically to said axis (A) to form a V-shape at the tail end (13) of said fuselage (2); and iii) forming an angle between said surfaces (15a, 15b) to give said aircraft (1) a preliminary value of longitudinal static stability and lateral stability; wherein said surfaces (15a, 15b) contain respective end edges (16a, 16b) opposite said fuselage (2); wherein said first and second surfaces (15a, 15b) comprise: - respective first surfaces (17a, 17b) facing each other; - respective second surfaces (18a, 18b) opposite the respective first surfaces (17a, 17b); and - respective end edges (16a, 16b) opposite said fuselage (2) from which the associated said winglets (19a, 19b) continue; and each specified winglet (19a, 19b) contains: - the corresponding first cantilever section (20a, 20b) extending from the associated end edge (16a, 16b) from the said corresponding first surface (17a, 17b); at the same time, starting from the associated specified end edge (16a, 16b), the specified first sections (20a, 20b) converge towards each other, characterized in that it contains steps in which: iv) two winglets (19a, 19b) are made, which are located transversely to the respective specified surfaces (15a, 15b) fixed relative to the specified respective surfaces (15a, 15b) and extend from the respective end edges (16a, 16b) of the respective specified surfaces (15a, 15b). ); and v) determining the area of said winglets (19a, 19b) and the inclination of said winglets (19a, 19b) with respect to respective said surfaces (15a, 15b) based on a correction value of said longitudinal static stability and lateral stability; wherein said steps iv) and v) are performed after said steps i), ii) and iii), and each said winglet (19a, 19b) further comprises a respective second portion (21a, 21b) extending in a cantilever manner from the associated end edge (16a, 16b) on the side of said respective second surface (18a, 18b); wherein, starting from the associated said end edge (16a, 16b), said second portions (21a, 21b) diverge from each other.

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