Helicopter, helicopter kit and associated reconfiguration method

Abstract

A helicopter (1) is described, comprising a fuselage (2) elongated along a first axis (X) and extending between a nose (6) and a tail boom (7); a horizontal tail (9) having a pair of first aerodynamic surfaces (11) elongated along a second axis (Y); the first and second axes (X, Y) defining a first plane (Q); the helicopter (1) comprising a pair of elements (20) transverse to the first aerodynamic surfaces (11); and a pair of second aerodynamic surfaces (21) generating respective second aerodynamic forces, connected with the first elements (20) and facing and spaced apart from the respective first aerodynamic surfaces (11); each second aerodynamic surface (21) comprising a first root end (80) connected with the respective element (20), a second free end (81) spaced apart from the tail boom (7), a first leading edge (55), a first trailing edge (56) opposite the first leading edge (55), a first chord (C1) at the first root end (80) parallel to the first axis (X) and a second chord (C2) at the second free end (81); the first and second chords (C1, C2) defining a second plane (R) tilted with respect to the first plane (Q).

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to European Patent Application No. 20164164.4, filed on March 19, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to helicopters, helicopter kits, and methods for reconfiguring helicopters. Background Technology

[0004] A helicopter, in a known manner, comprises a fuselage, a main rotor protruding from the fuselage and capable of rotating about a first axis, and a tail rotor protruding from the fuselage and capable of rotating about a second axis transverse to the first axis.

[0005] Specifically, the main rotor is adapted to provide the lift required to keep the helicopter in the air and to allow the helicopter to move forward / backward and laterally. Conversely, the tail rotor is adapted to counteract the rotation of the helicopter caused by the reaction torque transmitted to the fuselage through the operation of the main rotor and to control the yaw of the helicopter, i.e., rotation about the first axis.

[0006] Helicopters also include, in known ways:

[0007] The nose and tail beams are respectively located at opposite ends of the fuselage;

[0008] The vertical tail fin cantilever extends upwards from the tail boom of the fuselage and supports the tail rotor in a manner that allows it to rotate around a second axis; and

[0009] The horizontal tail, which protrudes laterally from the tail boom into the fuselage in a cantilever manner, is called the pitch stabilizer.

[0010] The horizontal tail is configured as a wing profile that, when the helicopter is in forward flight, generates a first aerodynamic force, lift / negative lift, with a primary component oriented parallel to a first axis.

[0011] This lift / negative lift, added to the lift generated by the main rotor, effectively maintains the helicopter's attitude in a stable state during high-speed forward flight; that is, ensures that the helicopter is in a stable equilibrium position regarding its vertical direction and its rotation about a longitudinal third axis around the helicopter. Specifically, the third axis is parallel to the fuselage's extension from the nose towards the tail boom and transverse to the first and second axes.

[0012] However, at certain low speeds, it may happen that the airflow guided downward by the main rotor deflects toward the tail of the fuselage, thereby impacting the horizontal tail and thus generating a third aerodynamic force on it, namely downward thrust.

[0013] After acceleration and / or deceleration of the helicopter, this thrust induces a nose-up attitude on the helicopter, i.e. an attitude in which the nose of the fuselage is higher than the tail of the fuselage. This nose-up attitude must be continuously corrected by the pilot acting on the cyclic pitch of the main rotor, i.e. by tilting the main rotor disc forward to move the airflow away from the horizontal tail.

[0014] This makes the piloting difficult for the pilot in certain low speed conditions.

[0015] Moreover, the nose-up attitude during the landing phase causes visibility problems for the pilot, which can become more problematic in the presence of gusts, adverse weather conditions or obstacles in the landing area.

[0016] Due to the above, the design of the horizontal tail must satisfy two conflicting constraints.

[0017] More in detail, on the one hand, a large horizontal tail surface is required to generate sufficient first aerodynamic values and thus increase the longitudinal stability of the helicopter.

[0018] On the other hand, a small horizontal tail surface is optimal at low speed to reduce the surface exposed to the downward airflow generated by the main rotor and the consequent amount of nose-up of the helicopter and thus improve the visibility and maneuverability of the helicopter in particularly critical situations, such as landing.

[0019] Due to these constraints, various horizontal tail configurations have been used on helicopters since the 1950s without achieving an optimal solution. For example, there are known asymmetric horizontal tails arranged at different heights with respect to the tail boom on only one side of the fuselage and there are symmetric solutions with two stabilizers arranged at different heights and different longitudinal positions with respect to the fuselage.

[0020] US 8,985,500 describes a helicopter comprising a horizontal tail comprising:

[0021] a pair of stabilizers protruding in cantilevered fashion from respective sides of the tail boom;

[0022] a pair of aerodynamic appendices superimposed on the respective stabilizers and protruding in cantilevered fashion from respective sides of the fuselage; and

[0023] a pair of end plates opposite the respective sides and extending between each stabilizer and the related appendix.

[0024] When the helicopter is in high speed forward flight, the aerodynamic wash generated by the fuselage and the main rotor significantly disturbs the airflow that hits the part of the fuselage adjacent to the appendix.

[0025] Therefore, these portions are aerodynamically "in the shade" and are not able to effectively contribute to the generation of the second aerodynamic force required to longitudinally stabilize the helicopter.

[0026] Therefore, the industry is aware of the need to optimize the aerodynamic behavior of the horizontal tail in order to increase the longitudinal stability of the helicopter in forward flight, while limiting the nose-up phenomenon in low-speed conditions.

[0027] The industry is also aware of the need to optimize the aerodynamic behavior of the horizontal tail in terms of angle of attack characteristics for forward flight, lateral flight and low-speed phases of landing / take-off, thus limiting any increase in maximum aerodynamic force and / or size generated at the typical angle of attack of the stall.

[0028] More specifically, the industry is obviously aware of the need to obtain a usable horizontal tail capable of minimizing as much as possible the effects of the downward airflow generated by the main rotor at low speeds.

[0029] The industry is obviously aware of the need to obtain a usable horizontal tail capable of maximizing as much as possible the aerodynamic efficiency of the horizontal tail.

[0030] EP-A-2878536 discloses a helicopter according to the preamble of claim 1, a kit for a helicopter according to the preamble of claim 12 and a method of reconfiguring a helicopter according to the preamble of claim 15. SUMMARY

[0031] The object of the present application is to produce a helicopter capable of satisfying at least one of the above needs in a simple and inexpensive manner.

[0032] According to the present application, the above object is achieved by a helicopter according to claim 1.

[0033] The present application also relates to a kit for a helicopter according to claim 12.

[0034] The present application also relates to a method of reconfiguring a helicopter according to claim 15. BRIEF DESCRIPTION OF DRAWINGS

[0035] For a better understanding of the present application, preferred and non-limiting embodiments thereof will be described hereinafter, purely by way of example and with reference to the attached drawings, in which:

[0036] Figure 1 is a perspective view of a helicopter made according to the present application;

[0037] Figure 2 is Figure 1a view from above, in scale and enlarged, of the tail portion of the helicopter of

[0038] Figure 3 is Figure 1 and Figure 2 a perspective view, in scale and enlarged, of the tail portion of the helicopter of

[0039] Figure 4 is Figures 1 to 3 a view from above, in scale and enlarged, of some details of the helicopter of

[0040] Figure 5 is Figure 4 a front view of a detail of the helicopter of

[0041] Figure 6 is Figure 4 and Figure 5 a perspective view of a detail

[0042] Figure 7 is Figures 4 to 6 a side view of a detail of the helicopter of

[0043] Figure 8 is Figures 4 to 7 a view, in scale and further enlarged, of some details of the helicopter of DETAILED DESCRIPTION

[0044] With reference to the attached drawings, reference 1 indicates a helicopter made according to the provisions of the present application.

[0045] The helicopter 1 essentially comprises a fuselage 2, a main rotor 3 arranged at the top of the fuselage 2, and a tail rotor 5.

[0046] The fuselage 2 comprises, at its opposite ends, a nose 6 and a tail boom 7.

[0047] It is possible to define:

[0048] a roll axis X of the helicopter 1, corresponding to the direction of longitudinal extension of the fuselage 2;

[0049] a pitch axis Y, orthogonal to the axis X; and

[0050] a yaw axis Z, orthogonal to the axes X and Y.

[0051] The axes X, Y, Z are integral with the helicopter 1 and pass through the center of gravity G of the helicopter 1 (not shown in the correct position in the drawings for simplicity of representation).

[0052] It is also possible to define:

[0053] a plane P, orthogonal to the axis Y and parallel to the axes X, Z;

[0054] a plane Q, which is orthogonal to the axis Z and parallel to the axes X, Y.

[0055] In particular, the plane P is a longitudinal plane of the helicopter 1 and the plane Q is a transverse plane of the helicopter 1.

[0056] It should be noted that in the following of the present description, terms such as “above”, “below”, “lateral”, “in front”, “in rear” and the like are used with reference to the normal forward direction of the helicopter 1 flying forward at constant height, i.e. in a condition in which the axis Z is vertical and the axes X, Y are horizontal.

[0057] The main rotor 3 is adapted to provide a thrust having a main component parallel to the axis Z, so as to be able to maintain the helicopter 1 in the air, move it forward or backward parallel to the axis X and lateral movements in the two directions parallel to the axis Y.

[0058] The tail rotor 5 is adapted to provide a thrust having a main component parallel to the axis Y. This thrust generates a torque around the axis Z in a direction opposite to the reaction torque acting on the fuselage 2 after the operation of the main rotor 3, so as to control the yaw angle of the helicopter 1.

[0059] The nose 6 and the tail boom 7 are opposite to each other along the longitudinal extension axis X of the helicopter 1.

[0060] The helicopter 1 further comprises:

[0061] a vertical tail 8, which protrudes in cantilevered fashion from the top of the tail boom 7 at an end opposite to the nose 6; and

[0062] a horizontal tail 9, which protrudes in cantilevered fashion from the tail boom 7 below the vertical tail 8 and is adapted to longitudinally (i.e. along the axis X) stabilize the helicopter 1.

[0063] The vertical tail 8 supports the tail rotor 5.

[0064] The horizontal tail 9 is adapted to generate aerodynamic forces having a main component parallel to the axis Z, so as to longitudinally stabilize the helicopter 1 in forward flight, i.e. to stabilize the attitude of the helicopter 1 in terms of rotation around the axis Y.

[0065] More in detail, the horizontal tail 9 comprises a pair of stabilizers 14 arranged on respective mutually opposite sides of the tail boom 7.

[0066] Since the stabilizers 14 are identical to each other, in the following description only one stabilizer 14 will be mentioned.

[0067] The stabilizer 14 has a length parallel to the axis Y, a width parallel to the axis X and a thickness parallel to the axis Z.

[0068] The stabilizer 14 comprises a bearing surface 11 configured to generate a lift / downlift having a prevailing component parallel to the axis Z.

[0069] The surface 11 of the stabilizer 14 is in turn delimited by:

[0070] a leading edge 15, which faces the nose 6 and defines a first, forwardmost edge of the stabilizer 14;

[0071] a trailing edge 16, which is opposite the leading edge 15 along the axis X and defines a second, rearmost edge of the stabilizer 14;

[0072] a top surface 17, which is delimited between the leading edge 15 and the trailing edge 16 and defines an upper surface of the stabilizer 14; and

[0073] a bottom surface 18, which is delimited between the leading edge 15 and the trailing edge 16 on the opposite side of the top surface 17 and defines a lower surface of the stabilizer 14.

[0074] The surface 11 further comprises a pair of end edges 12a, 12b opposite each other and parallel to the axis Y. The end edge 12a of each surface 11 is fixed to the tail boom 7.

[0075] The surface 11 has a chord B ( Figure 3 and Figure 4 ) joining the leading edge 15 and the trailing edge 16 in a rectilinear manner parallel to the axis X.

[0076] The length of the chord B is constant.

[0077] Advantageously, the stabilizer 14 comprises:

[0078] a plate 20 projecting in cantilevered manner transversely to the surface 11; and

[0079] an accessory 21 generating a second air dynamic, which is connected with the respective plate 20 and faces the surface 11 at a distance;

[0080] The accessory 21 in turn comprises:

[0081] a root end 80 connected with the plate 20;

[0082] a free end 81 opposite the root end 80, which is spaced from the tail boom 7 and the vertical tail 8;

[0083] a leading edge 55;

[0084] a trailing edge 56 opposite the leading edge 55;

[0085] a chord C1 ( Figure 2 , Figure 6 parallel to the axis X.Figure 7 ), which wing chord CI links the leading edge 55 and the trailing edge 56 in a rectilinear manner at the free end 81;

[0086] a wing chord C2 parallel to the axis X, which wing chord C2 links the leading edge 55 and the trailing edge 56 in a rectilinear manner at the root end 80;

[0087] the wing chords CI and C2 define a plane R inclined with respect to the plane Q. Figure 5 ).

[0088] More in detail, the plane R is inclined with respect to the plane Q by a non-zero angle a comprised between 0 and 30 degrees, more specifically between 0 and 15 degrees Figure 5 ).

[0089] Therefore, it is possible to desirably control the distance between the surface 11 and the appendages 21, thus minimizing the negative effects due to the mutual interference between the surfaces.

[0090] The appendages 21 also extend from the plates 20 towards the fuselage of the helicopter 1.

[0091] The appendages 21 also extend from the plates 20 at an increasingly greater distance from the surface 11.

[0092] In other words, the appendages 21 mutually converge on the side opposite the respective surface 11 from their respective plate 20 Figure 2 ).

[0093] In the case shown, the wing chord CI is shorter than the wing chord C2.

[0094] More specifically, the length of the wing chord C of the appendages 21 decreases from the wing chord C2 towards the wing chord CI Figure 2 ).

[0095] The appendages 21 also have a swept wing.

[0096] More specifically, in a plan view of the helicopter 1 from above, the wing chord CI has a portion C3 which protrudes from the surface 11.

[0097] Similarly, in a plan view of the helicopter 1 from above, the wing chord C2 has a portion C4 which protrudes from the surface 11 Figure 4 ).

[0098] The length of each portion C3, C4 parallel to the axis X is comprised between -50% and 50% of the wing chord B of the surface 11.

[0099] In a plan view of the helicopter 1, the length of each portion C3, C4 has a positive value when the portion C3 protrudes from the leading edge 15 of the surface 11 towards the nose 6.

[0100] On the contrary, in the plan view of the helicopter 1, the length of each portion C3, C4 has a negative value when the portion C3, C4 projects from the trailing edge 16 of the surface 11 towards the tail boom 7.

[0101] In the case shown, the portions C3, C4 project from the leading edge 15 of the surface 11 towards the nose 6 of the helicopter 1.

[0102] The portion C4 is also shorter than the portion C3.

[0103] Therefore, the appendage 21 has a negative sweepback wing and it is staggered with respect to the surface 11 towards the nose 6.

[0104] More in detail, an aerodynamic surface has a negative sweepback wing when it has a forward position (i.e. directed towards the nose 6) with respect to the same position corresponding to a quarter of the chord of the relative root (thus directed backwards or towards the opposite vertical tail 8 side) at a quarter of the chord corresponding to the free end.

[0105] In particular, the leading edge 55 is directed towards the nose 6 and defines a first end edge more forward than the appendage 21 with reference to the normal forward direction of the helicopter 1.

[0106] The trailing edge 56, opposite the leading edge 55 along the axis X, is directed towards the opposite side of the nose 6 and defines a second end edge more rearward than the appendage 21 with reference to the normal forward direction of the helicopter 1.

[0107] The appendage 21 also comprises:

[0108] a top surface 57, delimited between the leading edge 55 and the trailing edge 56 and defining the upper surface of the appendage 21; and

[0109] a bottom surface 58, delimited between the leading edge 55 and the trailing edge 56 on the opposite side of the top surface 57 and defining the lower surface of the appendage 21.

[0110] The plate 20, opposite the vertical tail 8 along the axis Y, is connected to the surface 11 and projects upwards from the edge 12b of the surface 11 in a cantilevered manner.

[0111] More in detail, the plate 20 is delimited by an edge 30 connected to the edge 12b of the surface 11 and by an edge 31 opposite the edge 30 parallel to the axis Z.

[0112] In the case shown, the appendage 21 and the plate 20 are connected by a sharp edge. In particular, the edge 31 and the root end 80 coincide with each other. Figure 2 and Figure 3 In the case shown, the appendage 21 and the plate 20 are connected by a sharp edge. In particular, the edge 31 and the root end 80 coincide with each other.

[0113] The edges 30, 31 extend parallel to the axis X.

[0114] An edge 31 is also provided above edge 30 and to which attachment 21 is connected.

[0115] In particular, edge 31 is further from vertical tail 8 than edge 30. Therefore, along axis Y, edge 30 is interposed between edges 31.

[0116] Panel 20 is also delimited by:

[0117] a front edge 48, which faces nose 6 and which defines a first, most forward edge of panel 20;

[0118] a rear edge 49, which is opposite front edge 48 along axis X and which defines a second, most rearward edge of panel 20;

[0119] a wall 51, delimited between front edge 48 and rear edge 49, which defines a surface of panel 20 directed towards vertical tail 8; and

[0120] a wall 52, delimited between front edge 48 and rear edge 49 on the side opposite wall 59, which defines a surface of panel 51 opposite vertical tail 8.

[0121] Panel 20 also comprises a plurality of chords D( Figure 6 ) each extending in a rectilinear manner between front edge 55 and rear edge 56.

[0122] Chords D1, D2 of panel 20 at edges 30, 31 define a plane S.

[0123] In the case shown, plane S is orthogonal to plane R, as shown by way of example in the attached Figure 5 diagram.

[0124] More in detail, plane S defines with axis Z an angle β which is between -30 degrees and 30 degrees, even more preferably between -20 degrees and 20 degrees. Figure 5 Therefore, it is possible to desirably control the joint between panel 20 and attachment 21, thus minimizing the negative effects due to the reciprocal interference between the surfaces.

[0125] Angle β is oriented so as to be positive when planes S diverge from each other with respect to axis Z and negative when these planes converge with respect to axis Z.

[0126] In the case shown, planes S diverge from each other with respect to axis Z, proceeding from surface 11 towards the relative attachment 21. Figure 5

[0127] Plane S also defines with axis X an angle γ which is between -15 degrees and 15 degrees, even more preferably between -10 degrees and 10 degrees.​Figure 4 ).

[0128] Therefore, it is possible to modify the pressure field generated on the elements 11 and 21, in particular the local concavity, and therefore to obtain values of efficiency greater than the entire horizontal tail 9.

[0129] When the planes S converge / diverge with respect to the axis X as one proceeds from the vertical tail 8 towards the nose 6, the angle γ is oriented so as to result positive / negative.

[0130] In the case illustrated, the planes S also converge with respect to the axis X as one proceeds from the vertical tail 8 towards the nose 6. Figure 4 ).

[0131] The plate 20 also comprises, proceeding from the edge 30 towards the edge 31: Figure 7 ) :

[0132] a portion 90 spaced from the edge 31, along the length of which the chord D is constant and equal to the value D1; and

[0133] a portion 91 spaced from the edge 30, along the length of which the chord D decreases from the value D1 to the value D2.

[0134] Each horizontal tail 9 also comprises an additional element 100 projecting in cantilevered fashion 12b from the relative surface 11 on the opposite side of the relative plate 20. The plate 20 is arranged below the surface 11 Figure 5 ).

[0135] In particular, each element 100 comprises:

[0136] a root end 101 connected with the edge 12b of the relative surface 11 and with the edge 30 of the relative plate 20;

[0137] a free end 102 opposite the root end 101.

[0138] Each additional element 100 also comprises:

[0139] a leading edge 111 directed towards the nose 6 and defining a first end edge more forward than the plate 20; and

[0140] a trailing edge 112 opposite the leading edge 111 along the axis X, which defines a second end edge more rearward than the plate 20.

[0141] Each element 100 also comprises a plurality of chords E each extending in rectilinear fashion between the leading edge 111 and the trailing edge 112.

[0142] The length of the chord E at the root end 101 is indicated as E1.

[0143] The chord E presents a gradually decreasing value from the root end 101 towards the free end 102. Figure 6 ).

[0144] The chord E defines a plane T Figure 5 ).

[0145] In the case illustrated, the plane T is parallel to the plane P and orthogonal to the plane Q.

[0146] In the case illustrated, the distance between the chord E1 and the free end 102 along the plane T is less than the distance between the chords D1, D2 along the plane S. Figure 5

[0147] With reference to Figure 3 each surface 11 also comprises a pair of flaps 50 (also known as Gurney flaps) applied to respective opposite sides of the relative trailing edge 56, lying on the same plane and both orthogonal to the trailing edge 56 so as to form a T shape.

[0148] In particular, each surface 11 comprises a region 53 which is adjacent to the plate 20 parallel to the axis Y and is interposed between a portion 106 of the leading edge 15 and a corresponding portion 107 of the trailing edge 16 parallel to the axis X Figure 2 and Figure 4 ).

[0149] More in detail, each region 53 defines an extension of the relative surface 11.

[0150] In particular, the leading edge, the trailing edge, the top surface and the bottom surface of each region 53 are extensions of the leading edge 15, the trailing edge 16, the top surface 17 and the bottom surface 18 of the relative surface 11.

[0151] In the case illustrated, the span 60 of the region 53 (i.e. the extension parallel to the axis Y) is between about 5% and 35%, preferably between 10% and 20% of the span 61 of the appendage 21.

[0152] With reference to Figure 5 the distance between the chords D1 and D2, measured on the plane S, i.e. the “height” of the plate 20, is between 10% and 100% of the length of the chord B of the surface 11.

[0153] With reference to Figure 6 and Figure 7 a chord E2 can be identified, provided towards the free end 102, which has a smaller length than the chord E1, which is closer to the root end 101. The chord E2 is provided parallel to the chord E1.

[0154] The length of the chord E gradually decreases from the length of the chord E1 to the length of the chord E2.

[0155] ​The distance between the chords E1 and E2 measured on the plane T, i.e. the height of the element 100, is between 10% and 100% of the length of the chord B of the surface 11.

[0156] The length of the chord C2 is between 20% and 100% of the length of the chord B of the surface 11.

[0157] The length of the chord C1 is between 20% and 100% of the length of the chord C2.

[0158] Alternatively, as shown in Figure 1 and Figures 4 to 8 The stabilizer 14 comprises a joint portion 120 interposed between the root end 80 of the appendage 21 and the edge 31 of the plate 20.

[0159] The portion 120 extends from the edge 31 towards the end 80 at a distance from the surface 11 which gradually increases and from the vertical tail 8 which gradually decreases.

[0160] The length of the chord of the portion 120 gradually decreases from the value D2 to the value C2.

[0161] The plate 20, the appendage 21, the area 53 of the stabilizer 14 and the Gurney flap 50 form a reconfiguration kit 85 for the stabilizer of a helicopter comprising only the surface 11. Figure 2 ).

[0162] The operation of the helicopter 1 is described starting from a low speed, typical of the take-off / landing phase, or hovering condition.

[0163] In this condition, the reaction torque around the axis Z generated on the fuselage 2 by the operation of the main rotor 3 is substantially balanced by the tail rotor 5. In fact, due to the low or zero speed of the helicopter 1, the aerodynamic forces generated by the vertical tail 8 are negligible.

[0164] Furthermore, in this condition, the downward wash coming from the main rotor 3 towards the tail boom 7 hits the stabilizer 14 of the horizontal tail 9.

[0165] The appendage 21 arranged above the surface 11 hinders the passage of this wash towards the surface 11, which is therefore subjected to a particularly low or zero downward thrust generated by the wash of the main rotor 3.

[0166] Furthermore, the small overall extension of the appendage 21 is able to further reduce the downward thrust exerted by this wash on the horizontal tail 9.

[0167] The moment around the axis Y, generated by this thrust, is therefore reduced, with a consequent reduction in the attitude changes of the helicopter 1 during the take-off / landing phase and in the corrections required by the pilot.

[0168] Furthermore, in these conditions, the horizontal tail 9 generates aerodynamic thrusts having a component parallel to the axis Z, which are able to keep the helicopter 1 in stable equilibrium in terms of translation along the axis Z and rotation around the axis Y.

[0169] The presence of the fuselage 2 interferes with the aerodynamic flow that hits the horizontal tail 9.

[0170] The kit 85 is used to reconfigure the helicopter, which is equipped with stabilizers each comprising only the surface 11, without the relative area 53.

[0171] More in detail, the area 53 of the kit 85 is placed alongside and connected to the relative surface 11 along the axis Y, so as to define a relative extension of the relative surface 11 and so that the relative appendix 21 faces the respective surface 11 at a distance and has a relative free end 81 spaced from the tail boom 7 / vertical tail 8 along the axis Y.

[0172] The advantages that can be obtained from this are evident, according to the examination of the characteristics of the helicopter 1, kit 85 and method according to the present application.

[0173] In particular, the appendix 21 of the stabilizer 14 generates aerodynamic forces and also has a respective free end 81 spaced from the tail boom 7 / vertical tail 8 and a relative plane R inclined with respect to Q by an angle a.

[0174] In this way, in the high-speed conditions, the aerodynamic lift / negative lift generated by the appendix 21 along the axis Z adds to the lift / negative lift generated by the surface 11 and contributes, on the one hand, to the main effect for increasing the longitudinal stability of the helicopter 1.

[0175] On the other hand, since the appendix 21 is spaced from the vertical tail 8, the stabilizer 14 is lighter and less voluminous than the stabilizers of the known solutions described in the introductory part of the present description, with evident advantages for the helicopter 1.

[0176] The reduction in weight is obtained without any disadvantage on the aerodynamic forces generated by the stabilizer 14, since the fuselage 2 and the main rotor 3 significantly interfere with the air flow that reaches the area between the appendix 21 and the vertical tail 8, making the generation of aerodynamic forces in this area rather inefficient.

[0177] In other words, the horizontal tail 9, with reduced weight, achieves a high longitudinal stability of the helicopter 1.

[0178] In the low speed condition, the surface 11 is in the turbulent wash of the appendages 21. Therefore, the downward thrust generated on the horizontal tail 9 by the wash of the main rotor 3 is reduced with respect to the traditional solution, thus reducing the tendency of the helicopter 1 to assume a nose-up attitude during the landing operations and improving the pilot's comfort and visibility.

[0179] The Applicant has observed that the downward thrust generated on the horizontal tail 9 by the flow of the rotor 3 can be further reduced thanks to the fact that the appendages 21 have respective free ends 81. The presence of the free ends 81 also allows to significantly reduce the overall induced drag of the horizontal tail 9, thus improving its aerodynamic efficiency.

[0180] In summary, the Applicant has observed that the introduction of the appendages 21 is able to increase the lift slope of the lift coefficient with respect to the angle of attack, thus reducing the increase of the maximum lift in the stall condition.

[0181] Since the angle of attack of the horizontal tail 9 corresponding to the normal flight conditions of the helicopter 1 - forward flight, lateral flight, hovering, low speed flight during take-off / landing - is less than the stall angle of attack, the appendages 21 are able to increase the value of the aerodynamic force generated by the horizontal tail 9 at the typical angles of attack at which the helicopter 1 operates.

[0182] The plane S defines with the axis Z an angle β comprised between -30 degrees and +30 degrees, preferably between -20 degrees and +20 degrees.

[0183] Therefore, the joint between the panel 20 and the appendages 21 can be desirably controlled, thus minimizing the negative effects due to the mutual interference between the surfaces.

[0184] The plane S also defines with the axis X an angle γ comprised between -15 degrees and 15 degrees, preferably between -10 degrees and 10 degrees.

[0185] Therefore, it is possible to modify the pressure field generated on the elements 11, 20 and 21, in particular the local concavities, thus obtaining a desired efficiency value greater than the entire horizontal tail 9. The portions C3 and C4 of each appendage 21 have a length parallel to the axis X comprised between -50% and 50% of the chord B of the relative surface 11.

[0186] Thanks to this, the appendages 21 have a rear-swept wing and are staggered with respect to the relative surface 11 along the axis X. Therefore, it is possible to control the interaction between the downward flow generated by the rotor 3 and the horizontal tail 9 during the low speed flight conditions, partially placing the surface 11 in line with the appendages 21 longitudinally.

[0187] The flap 50 applied orthogonally to the trailing edge 56 of the surface 11 enables to increase the aerodynamic force generated by the horizontal tail 9 with respect to a small increase in the aerodynamic resistance. In particular, thanks to the T shape of the flap 50 and the corresponding trailing edge 56, it is possible to increase the lift / negative lift generated by the surface 11 and the associated maximum of the lift coefficient as a function of the angle of attack.

[0188] The kit 85 enables to reconfigure a helicopter with a traditional horizontal tail by simply fixing the region 53 to the surface 11 so as to define an extension of the surface 11 and set the appendage 21 facing the surface 11 and spaced from the tail boom 7 / vertical tail 8.

[0189] Thanks to the spacing of the appendage 21 from the tail boom 7 / vertical tail 8, the application of the kit 85 does not require any action on the tail boom 7, thus greatly simplifying the reconfiguration of the helicopter 1.

[0190] The T-shaped flap 50 is particularly advantageous when included in the kit 85. In fact, the T shape allows to increase the lift generated by the stabilizer 14 with respect to the absence of the kit 85, without changing the attitude of the helicopter 1.

[0191] Obviously, modifications and variants can be made to the helicopter 1, the kit 85 and the method set forth herein without departing from the scope defined in the claims.

[0192] In particular, each stabilizer 14 can comprise at least one first additional appendage 21 arranged on the top surface 17 side of the surface 11 and spaced from the vertical tail 8 along the axis Y, and at least one second additional appendage 21 arranged on the bottom surface 18 side of the surface 11 and spaced from the tail boom 7 along the axis Y.

[0193] In particular, the first additional appendage 21 can be more than one and / or the second additional appendage 21 can be more than one.

[0194] Alternatively, each stabilizer 14 can comprise at least two first additional appendages 21 arranged on the top surface 17 side of the surface 11, spaced from the vertical tail 8 and staggered along the axis X. Alternatively, each stabilizer 14 can comprise at least two second additional appendages 21 arranged on the bottom surface 18 side of the surface 11, spaced from the vertical tail 8 and staggered along the axis X.

[0195] The first and second additional appendages 21 allow to increase the aerodynamic force generated by the horizontal tail 9 and, therefore, to improve the stabilizing effect at high speed, further increasing the shielding effect of the surface 11 on the downward flow generated by the rotor 3.

[0196] Alternatively, the length of the portions C3, C4 of each appendix 21 can be the same. In this case, each appendix 21 will be simply staggered with respect to the relative surface 11, either towards the nose 6 or towards the tail beam 7, without any geometric sweepback wing.

[0197] The chords B, C, D, E of the surfaces 11, of the appendixes 21, of the plates 20 and of the elements 100 can be curved, i.e. obtained by rotating the relative planes R, S, T by a constant angle. In this case, the planes R; S; T will identify the planes defined by the chords C1, C2; D1, D2; E1, E2 without curvature.

Claims

1. A helicopter (1) comprising: - a fuselage (2) elongated along a first axis (X) longitudinal of the helicopter (1) and extending between a nose (6) and a tail boom (7) of the helicopter (1), a vertical tail (8) protruding from the tail boom (7); - a main rotor (3) provided at the top of the fuselage (2); - a horizontal tail (9) provided at the tail boom (7) and transversal to the tail boom (7); the horizontal tail (9) defining a pair of first aerodynamic surfaces (11) generating in use respective first aerodynamic forces and elongated along a second axis (Y) transversal to the first axis (X); the first axis (X) and the second axis (Y) defining a first plane (Q); - a pair of first elements (20) transversal to the respective first aerodynamic surfaces (11); and - a pair of second aerodynamic surfaces (21) generating in use respective second aerodynamic forces, connected to the respective first elements (20) and facing and spaced apart from the respective first aerodynamic surfaces (11); each second aerodynamic surface (21) in turn comprising: - a first root end (80) connected to the respective first element (20); - a second free end (81); - a first leading edge; - a first trailing edge opposite to the first leading edge; - a first chord (C2) joining the first leading edge and the first trailing edge at the first root end (80) parallel to the first axis (X); and - a second chord (C1) joining the first leading edge and the first trailing edge at the second free end (81) parallel to the first axis (X); the first chord (C2) and the second chord (C1) defining a second plane (R) tilted with respect to the first plane (Q); characterized in that the second free end (81) is spaced apart from the tail boom (7) and opposite to the first root end (80); the second chord (C1) is defined at the second free end; the first plane (Q) and the second plane (R) are tilted by a non-zero angle (a) between each other, the non-zero angle (a) being between 0 and 30 degrees.

2. The helicopter according to claim 1, characterized in that the non-zero angle (a) is between 0 and 15 degrees.

3. The helicopter according to claim 1 or 2, characterized in that each first element (20) comprises: - a third end connected to the respective first aerodynamic surface (11); - a fourth end opposite to the third end and connected to the respective second aerodynamic surface (21); - a second leading edge; - a second trailing edge; - a third chord (D1) joining the second leading edge and the second trailing edge at the third end; - a fourth chord (D2) joining the second leading edge and the second trailing edge at the fourth end; the third chord (D1) and the fourth chord (D2) defining a third plane (S); said third plane (S) is inclined with respect to said first axis (X) of a second angle (γ) comprised between -15 degrees and 15 degrees, and / or said third plane (S) is inclined with respect to a third axis (Z) orthogonal to said first plane (Q) of a third angle (β) comprised between -30 degrees and 30 degrees.

4. The helicopter of claim 1, wherein, each said second aerodynamic surface (21) has a respective fifth chord (C) which travels from the respective first element (20) towards the respective second free end (81) and from said first chord (C2) to said second chord (Cl), said fifth chord (C) having a length which gradually decreases.

5. The helicopter according to claim 1 or 2, characterized in that said second aerodynamic surface (21) starts from the respective first element (20) and converges on the opposite side of said first aerodynamic surface (11) to each other.

6. The helicopter according to claim 1 or 2, characterized in that each said first element (20) comprises a respective portion (91) which is spaced apart from the relative first aerodynamic surface (11) and is connected to the relative second aerodynamic surface (21); each said portion (91) has a respective sixth chord (D) which travels towards the relative second aerodynamic surface (21), said sixth chord (D) gradually decreasing; said sixth chord (D), travelling towards the relative second aerodynamic surface (21), has a length greater than or equal to said first chord (C2).

7. The helicopter according to claim 1 or 2, characterized in that each said second aerodynamic surface (21) extends from the relative first element (20) towards the nose (6) of the helicopter (1) and has a negative backward swept wing and / or is staggered with respect to said first aerodynamic surface (11).

8. The helicopter according to claim 1 or 2, characterized in that each said second aerodynamic surface (21) tapers from said first root end (80) towards said second free end (81).

9. The helicopter according to claim 3, characterized in that, said third plane (S) extends from the respective first aerodynamic surface (11) diverging from each other with respect to a third axis (Z) which is orthogonal to said first axis (X) and to said second axis (Y).

10. The helicopter of claim 3, wherein, said third plane (S) extends converging from each other with respect to said first axis (X) from said tail boom (7) towards said nose (6) of the helicopter (1).

11. The helicopter according to claim 3, characterized in that, it comprises a pair of second elements (100); each said second element (100) is connected at a respective third root end (101) to a respective first aerodynamic surface (11) and to the respective first element (20) and extends on the opposite side of the relative first element (20) with respect to the relative first aerodynamic surface (11); each said second element (100) comprises: - a fourth free end (102) opposite the respective third root end (101); - a third leading edge (111); - a third trailing edge (112) opposite the third leading edge; - a seventh chord (El) joining the third leading edge (111) and the third trailing edge (112) at the third root end (101) and parallel to the first axis (X); and - an eighth chord (E2) joining the third leading edge (111) and the third trailing edge (112) at the fourth free end (102) and parallel to the first axis (X); the seventh chord (El) and the eighth chord (E2) define a fourth plane (T) which is inclined with respect to the third plane (S) and orthogonal to the first plane (Q).

12. The helicopter according to claim 3, characterized in that, the second angle (γ) is between -10 and 10 degrees.

13. The helicopter according to claim 3, characterized in that, the third angle (β) is between -20 and 20 degrees.

14. An upgrade kit (85) for a helicopter (1) having a main rotor (3) provided at the top of a fuselage (2), the upgrade kit (85) comprising: - areas (53) fixable to a first aerodynamic surface (11) defined by a horizontal tail (9) of the helicopter (1) so as to define an extension of the first aerodynamic surface (11) along a first axis (Y); - at least one first element (20) transverse to the areas (53); and - a second aerodynamic surface (21) transverse to the first element (20), adapted to generate, in use, aerodynamic forces and provided on the opposite side of the first element (20) with respect to the first aerodynamic surface (11); each of the areas (53) defines a first leading edge and a first trailing edge opposite each other along a second axis (X) transverse to the first axis (Y); the first axis (Y) and the second axis (X) define a first plane (Q); each of the second aerodynamic surfaces (21) comprises: - a first root end (80) connected to the respective first element (20); - a second free end (81) opposite the first root end (80); - a second leading edge; - a second trailing edge opposite the second leading edge; - a first chord (Cl) joining the second leading edge and the second trailing edge at the second free end (81) and parallel to the second axis (X); - a second chord (C2) joining the second leading edge and the second trailing edge at the first root end (80) and parallel to the first axis (X); the first chord (Cl) and the second chord (C2) define a second plane (R) inclined with respect to the first plane (Q); characterized in that the first chord (Cl) is defined at the second free end (81); the first plane (Q) and the second plane (R) are inclined to each other by a non-zero angle (a) between 0 and 30 degrees.

15. The kit of claim 14, wherein, the non-zero angle (a) is between 0 and 15 degrees.

16. The kit of claim 14 or 15, wherein, Each said first element (20) comprises a first edge connected with said region (53) and a second edge opposite to said first edge and connected with said second aerodynamic surface (21); Each said second aerodynamic surface (21) extends along a third axis (Z) orthogonal to said first plane (Q) at an increasing distance from said region (53), starting from said first edge of the relative first element (20).

17. An upgrading method for a helicopter (1) comprising: - a fuselage (2) elongated along a first axis (X) longitudinal of said helicopter (1) and extending between a nose (6) and a tail boom (7) of said helicopter (1); - a main rotor (3) arranged at the top of said fuselage (2); - a horizontal tail (9) arranged at said tail boom (7) and transversal to said tail boom (7); said horizontal tail (9) defining a pair of first aerodynamic surfaces (11) generating in use respective first air dynamics and elongated along a second axis (Y) transversal to said first axis (X); said first axis (X) and said second axis (Y) defining a first plane (Q); said method comprising the steps of: i) arranging at least one first element (20) transversal to said first aerodynamic surfaces (11); ii) connecting to said first element (20), at a position facing and spaced from said first aerodynamic surfaces (11), at least one second aerodynamic surface (21) generating a second air dynamic; Each said second aerodynamic surface (21) comprises: - a first root end (80) connected with the relative first element (20); - a second free end (81) opposite to said first root end (80); - a first leading edge; - a first trailing edge opposite to said first leading edge; - a first chord (CI) joining said first leading edge and said first trailing edge at said second free end (81) and parallel to said first axis (X); - a second chord (C2) joining said first leading edge and said first trailing edge at said first root end (80) and parallel to said first axis (X); said first chord (CI) and said second chord (C2) defining a second plane (R) inclined with respect to said first plane (Q); said method being characterized in that said second free end (81) is spaced from said tail boom (7) and from a vertical tail (8) protruding from said tail boom (7); said first chord (CI) being defined at said second free end (81); said first plane (Q) and said second plane (R) being inclined between each other of a non-zero angle (a) comprised between 0 and 30 degrees.

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