HYBRID HELICOPTER INCLUDING INCLINED PROPULSION PROPELLERS

Abstract

The present invention relates to a hybrid helicopter comprising a fuselage, a main rotor, two wings situated on either side of said fuselage, and two propulsion propellers situated respectively on each wing. Each propulsion propeller is inclined, and when it rotates it generates a thrust force (F.sub.d, F.sub.g) along a thrust axis (P.sub.d, P.sub.g) that is inclined relative to a longitudinal direction (X) of said hybrid helicopter. As a result, a longitudinal component and a transverse component of said thrust force (F.sub.d, F.sub.g) of each propulsion propeller act, during hovering flight of said hybrid helicopter, to generate respective torques that combine to form a moment (M.sub.stat) opposing a yaw torque (C.sub.R) of said hybrid helicopter.

Claims

1. A hybrid helicopter having a longitudinal direction (X) extending from the front of the hybrid helicopter towards the rear of the hybrid helicopter, an elevation direction (Z) extending upwards perpendicularly to the longitudinal direction (X), and a transverse direction (Y) extending from the left towards the right of the hybrid helicopter, perpendicularly to the longitudinal and elevation directions (X, Z), the hybrid helicopter comprising: a fuselage; a main rotor rotatable about a center of rotation (A); two wings situated on either side of the fuselage relative to a front-to-rear plane (XZ) formed by the longitudinal direction (X) and the elevation direction (Z); at least two propulsion propellers situated transversely on either side of the front-to-rear plane (XZ) of the hybrid helicopter at least one propulsion propeller being arranged on either each wing, each propulsion propeller having a thrust axis (P.sub.d, P.sub.g) along which a thrust force (F.sub.d, F.sub.g) is generated while the propulsion propeller is rotating; and a power plant driving the main rotor and each propulsion propeller in rotation; wherein the thrust axis (P.sub.d, P.sub.g) of each propulsion propeller is inclined relative to the longitudinal direction (X), with the thrust force (F.sub.d, F.sub.g) generated by each propulsion propeller while rotating comprising a longitudinal component and a transverse component, and each propulsion propeller is offset longitudinally relative to the center of rotation (A) of the main rotor in such a manner that the longitudinal component and the transverse component of the thrust force (F.sub.d, F.sub.g) of each propulsion propeller act during hovering flight of the hybrid helicopter to generate a respective moment (M.sub.stat) balancing a yaw torque (C.sub.R) of the hybrid helicopter.

2. The hybrid helicopter according to claim 1, wherein the hybrid helicopter has two propulsion propellers, respectively a right propeller and a left propeller situated transversely on either side of the front-to-rear plane (XZ), the moment (M.sub.stat) generated by the thrust forces (F.sub.d, F.sub.g) of the two propulsion propellers being determined by the following equation:
M.sub.stat=F.sub.d((y.sub.d-y.sub.Rot)cos(.sub.d)(x.sub.d-x.sub.Rot)sin(.sub.d)) +F.sub.g((y.sub.g-y.sub.Rot)cos(.sub.g)(x.sub.Rot)sin(.sub.g)) F.sub.d, F.sub.g being the magnitude of the thrust force (F.sub.d, F.sub.g) generated by the rotation of the right or left propulsion propeller respectively; x.sub.d, x.sub.g being a longitudinal coordinate along the longitudinal direction (X) of the right and left propulsion propellers respectively; y.sub.d, y.sub.g being a transverse coordinate along the transverse direction (Y) of the right and left propulsion propellers respectively; x.sub.Rot being a longitudinal coordinate along the longitudinal direction (X) of the center of rotation (A) of the main rotor; y.sub.Rot being the transverse coordinate along the transverse direction (Y) of the center of rotation (A) of the main rotor; and .sub.d, B.sub.g being an angle measured from the longitudinal direction (X) towards the thrust axis (P.sub.d, P.sub.g) of the right or left propulsion propeller respectively, with the counterclockwise direction being considered as positive.

3. The hybrid helicopter according to claim 1, wherein for the propulsion propellers, the angles (P.sub.d, P.sub.g) between the longitudinal direction (X) and the thrust axis (P.sub.d, P.sub.g) of each propulsion propeller are identical.

4. The hybrid helicopter according to claim 1, wherein the propulsion propellers are arranged behind the main rotor along the longitudinal direction (X), and the thrust axes (P.sub.d, P.sub.g) of the propulsion propellers converge towards the rear of the hybrid helicopter.

5. The hybrid helicopter according to claim 1, wherein the propulsion propellers are arranged in front of the main rotor along the longitudinal direction (X), and the thrust axes (P.sub.d, P.sub.g) of the propulsion propellers converge towards the front of the hybrid helicopter.

6. The hybrid helicopter according to claim 1, wherein the angle (.sub.d, .sub.g) between the longitudinal direction (X) and the thrust axis (P.sub.d, P.sub.g) of the propulsion propeller lies in the range 0 and a maximum angle .sub.max defined as a function of the position of the propulsion propeller relative to the center of rotation (A) of the main rotor, such that: ${}_{\max }=\mathrm{atan}\left(\frac{x-x_{\mathrm{Rot}}}{y-y_{\mathrm{Rot}}}\right)$

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The invention and its advantages appear in greater detail from the following description of embodiments given by way of illustration and with reference to the accompanying figures, in which:

[0067] FIG. 1 is a view of a hybrid helicopter;

[0068] FIGS. 2 and 3 are two plan views of a prior art hybrid helicopter; and

[0069] FIGS. 4 to 7 are plan views of a hybrid helicopter of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0070] Elements present in more than one of the figures are given the same references in each of them.

[0071] Each figure shows a hybrid helicopter 10, 20 having a fuselage 11, a tail boom 16, a main rotor 12, two propulsion propellers 13, and two wings 15. The hybrid helicopter 10, 20 has a power plant driving rotation of the main rotor 12 and of the propulsion propellers 13.

[0072] FIGS. 2 and 3 show a hybrid helicopter 20 of the prior art, whereas FIGS. 4 to 7 show two embodiments of a hybrid helicopter 10 of the invention.

[0073] In each figure, it should be observed that three directions X, Y, and Z are shown to form an (X, Y, Z) rectangular reference frame.

[0074] The first direction X is said to be longitudinal and extends from the front towards the rear of the hybrid helicopter 10, 20, i.e. from the front tip of the fuselage 11 of the hybrid helicopter 10, 20 to the rear end of its tail boom 16. The term longitudinal relates to any direction parallel to the longitudinal direction X.

[0075] The second direction Y is said to be transverse and it extends from the left to the right of the hybrid helicopter 10, 20. The term transverse relates to any direction that is parallel to the transverse direction Y.

[0076] Finally, the third direction Z is said to be in elevation and it extends upwards. The terms elevation and vertical relate to any direction parallel to the elevation direction Z.

[0077] The main rotor 12 of the hybrid helicopter 10, 20 has a plurality of main blades 121 and, while rotating about its center of rotation A, it serves to generate an aerodynamic force that provides the hybrid helicopter 10, with lift, and possibly also with propulsion. The center of rotation A of the main rotor 12 is close to the yaw axis of the hybrid helicopter 10, 20.

[0078] The two propulsion propellers 13 are situated transversely on either side of a front-to-rear plane XZ of the hybrid helicopter 10, 20 as formed by the longitudinal and elevation directions X and Z, and in particular they are situated on either side of the fuselage 11. Each propulsion propeller 13 has a plurality of secondary blades 131 and, while rotating, serves to generate a thrust force F.sub.d, F.sub.g directed along a thrust axis P.sub.d, P.sub.g of the propulsion propeller 13 for driving advance of the hybrid helicopter 10, 20.

[0079] The two wings 15 extend transversely on either side of the fuselage 11 so as to form a lift surface. A respective propulsion propeller 13 is positioned at each end of each wing 15.

[0080] At its rear end, the tail boom 16 has a substantially horizontal stabilizer 17 and two substantially vertical stabilizers 18. These stabilizers 17, 18 contribute in particular to stabilizing the hybrid helicopter 10, 20 aerodynamically in flight. The vertical stabilizers 18 also serve to generate a transverse aerodynamic force in cruising flight so as to oppose at least in part the yaw torque C.sub.R of the hybrid helicopter 10, 20 and/or so as to generate movement of the hybrid helicopter 10, 20 about its yaw axis.

[0081] In FIGS. 2 to 7, the main rotor 12 turns clockwise about the center of rotation A. Under such circumstances, the yaw torque C.sub.R is directed counterclockwise and is applied to the fuselage 11.

[0082] FIGS. 2 and 3 are two plan views of a prior art hybrid helicopter 20. The two propulsion propellers 13 are arranged on the wings 15 in such a manner that the thrust axes P.sub.d, P.sub.g of the two propulsion propellers 13 are parallel to the longitudinal direction X. FIG. 2 shows the prior art hybrid helicopter 20 during cruising flight, while FIG. 3 shows it during hovering flight.

[0083] For cruising flight, it can be seen that both propulsion propellers 13 supply identical thrust forces F.sub.d, F.sub.g directed towards the front of the prior art helicopter 20, along their respective thrust axes P.sub.d, P.sub.g. The vertical stabilizers 18 generate two transverse forces F.sub.T1, F.sub.T2 opposing the yaw torque C.sub.R of the hybrid helicopter 20. These two thrust forces F.sub.d, F.sub.g add together to form a traction force F.sub.tract of the hybrid helicopter 20 that is used to cause the hybrid helicopter 20 to advance and to enable it to fly at a high speed of advance. This traction force F.sub.tract as supplied jointly by the two propulsion propellers 13 for cruising flight is defined by the following equation:

F.sub.tract=F.sub.d+F.sub.g

[0084] For hovering flight, the two propulsion propellers 13 supply opposite thrust forces F.sub.d, F.sub.g directed along their thrust axes P.sub.d, P.sub.g and directed for a first propulsion propeller 13 towards the rear of the hybrid helicopter 20 and for a second propulsion propeller 13 towards the front of the hybrid helicopter 20.

[0085] Since the main rotor 12 rotates clockwise when seen from above, the thrust force F.sub.d of the right propulsion propeller 13 is directed towards the rear of the hybrid helicopter 20 and the thrust force F.sub.g of the left propulsion propeller 13 is directed towards the front, as shown in FIG. 3. As a result, the thrust forces F.sub.d and F.sub.g are used for generating a moment M.sub.stat opposing the yaw torque C.sub.R of the hybrid helicopter 20.

[0086] This moment M.sub.stat generated by the two propulsion propellers 13 for hovering flight is defined by the equation:

M.sub.stat=F.sub.d(y.sub.d, y.sub.Rot)+F.sub.g(y.sub.g-y.sub.Rot)

[0087] For both embodiments of a hybrid helicopter 10 of the present invention as shown in FIGS. 4 to 7, the two propulsion propellers 13 are arranged at the ends of respective wings 15 and they are inclined in such a manner that the thrust axes P.sub.d, P.sub.g of the two propulsion propellers 13 are inclined relative to the longitudinal direction X. Each thrust axis P.sub.d, P.sub.g thus forms an angle .sub.d, .sub.g with the longitudinal direction X in a horizontal plane parallel to the longitudinal and transverse directions X and Y.

[0088] In the first embodiment shown in FIGS. 4 and 5, the propulsion propellers 13 are arranged behind the center of rotation A of the main rotor 12, with the longitudinal coordinate x.sub.d, x.sub.g of each propulsion propeller 13 in the (X, Y, Z) reference frame being greater than the longitudinal coordinate x.sub.Rot of the center of rotation A of the main rotor 12, and such that their thrust axes P.sub.d, P.sub.g converge on each other towards the rear of the hybrid helicopter 10. FIG. 4 is a plan view of the hybrid helicopter 10 of the invention during cruising flight, while FIG. 5 is a plan view of the hybrid helicopter 10 during hovering flight.

[0089] For cruising flight, both propulsion propellers 13 supply thrust forces F.sub.d, F.sub.g of the same magnitude and directed towards the front of the hybrid helicopter 10 along their respective thrust axes P.sub.d, P.sub.g. Since each thrust force F.sub.d, F.sub.g acts along its thrust axis P.sub.d, P.sub.g and is thus inclined relative to the longitudinal direction X, it can be resolved into a longitudinal component and a transverse component. Since the thrust forces F.sub.d, F.sub.g are of the same magnitude, their transverse components cancel, since these two transverse components are directed in two opposite directions. Under such circumstances, the longitudinal components of these two thrust forces F.sub.d, F.sub.g add so as to form a traction force F.sub.tract for the hybrid helicopter 10 defined by the following equation:

F.sub.tract=F.sub.dcos(.sub.d)+F.sub.gcos(.sub.g)

[0090] This fraction force F.sub.tract supplied jointly by the two propulsion propellers 13 is then used to generate advance of the hybrid helicopter 10 and to enable it to fly at a high speed of advance.

[0091] Furthermore, during cruising flight, the vertical stabilizers 18 generate two transverse aerodynamic forces F.sub.T1, F.sub.T2 that oppose the yaw torque C.sub.R of the hybrid helicopter 10.

[0092] In hovering flight, the two propulsion propellers 13 supply thrust forces F.sub.d, F.sub.g directed along their respective thrust axes P.sub.d, P.sub.g and directed towards the rear of the hybrid helicopter 10 for a first propulsion propeller 13 and towards the front of the hybrid helicopter 10 for the second propulsion propeller 13. Since the main rotor 12 is rotating in the clockwise direction when seen from above, the thrust force F.sub.d of the right propulsion propeller 13 is directed towards the rear of the hybrid helicopter 10 while the thrust force F.sub.g of the left propulsion propeller 13 is directed towards the front, as shown in FIG. 5. Once more, each thrust force F.sub.d, F.sub.g can be resolved into a longitudinal component and a transverse component.

[0093] The longitudinal component of each thrust force F.sub.d, F.sub.g generates torque in the clockwise direction while applying a transverse lever arm equal to the difference between the transverse coordinate y.sub.d, y.sub.g of the thrust force F.sub.d, F.sub.g and the transverse component y.sub.Rot of the center of rotation A of the main rotor 12 in the (X, Y, Z) reference frame. Furthermore, the transverse component of each thrust force F.sub.d, F.sub.g also generates a clockwise torque while applying a longitudinal lever arm equal to the difference between the longitudinal coordinate x.sub.d, x.sub.g of the thrust force F.sub.d, F.sub.g and the longitudinal component x.sub.Rot of the center of rotation A of the main rotor 12. Under such circumstances, the longitudinal and transverse components of these two thrust forces F.sub.d, F.sub.g combine advantageously for generating a moment M.sub.stat about the center of rotation A that is equal to the sum of these torques and that serves to balance the yaw torque C.sub.R of the hybrid helicopter 10. This moment M.sub.stat is defined during hovering flight of the hybrid helicopter 10 in this first embodiment by the following equation:

M.sub.stat=F.sub.d((y.sub.d-y.sub.Rot)cos(.sub.d)(x.sub.d-x.sub.Rot)sin(.sub.d)) +F.sub.g((y.sub.g-y.sub.Rot)cos(.sub.g)(x.sub.g-x.sub.Rot)sin(.sub.g))

where the angle .sub.d, .sub.g is measured from the longitudinal direction X towards the thrust axis P.sub.d, P.sub.g as shown in FIGS. 4 and 5, and is considered to be positive in the counterclockwise (trigonometrical direction).

[0094] It can be seen that the moment M.sub.stat generated by the propulsion propellers 13 for the hybrid helicopter 10 in this first embodiment is advantageously greater than the moment M.sub.stat of a prior art hybrid helicopter 20 firstly because of the inclination of the thrust axis P.sub.d, P.sub.g of each propulsion propeller 13 and secondly because of the longitudinal lever arm applied to the thrust force F.sub.d, F.sub.g of each propulsion propeller 13, and more particularly to its transverse component. This increase in the moment M.sub.stat is accompanied by a small decrease in the traction force F.sub.tract of the propulsion propellers 13.

[0095] In the second embodiment shown in FIGS. 6 and 7, the propulsion propellers 13 are arranged in front of the center of rotation A of the main rotor 12, with the longitudinal coordinates x.sub.d, x.sub.g of each propulsion propeller 13 in the (X, Y, Z) reference frame being less than the longitudinal components x.sub.Rot of the center of rotation A of the main rotor 12, such that their thrust axes P.sub.d, P.sub.g converge on each other towards the front of the hybrid helicopter 10. FIG. 6 is a plan view of the hybrid helicopter 10 during cruising flight, while FIG. 7 is a plan view of the hybrid helicopter 10 during hovering flight.

[0096] Such an inclination of the thrust axes P.sub.d, P.sub.g of the propulsion propellers 13 in this second embodiment, combined with each propulsion propeller 13 being positioned longitudinally in front of the center of rotation A of the main rotor 12 has the same effects on the traction force F.sub.tract and on the moment M.sub.stat as the inclination of the thrust axes P.sub.d, P.sub.g of the propulsion propellers 13 in the first embodiment in combination with those propulsion propellers 13 being longitudinally positioned behind the center of rotation A of the main rotor 12, i.e. there is an increase in the moment M.sub.stat generated by the propulsion propellers 13 and a slight reduction in the traction force F.sub.tract of the propulsion propellers 13.

[0097] The moment M.sub.stat is then defined during hovering flight of the hybrid helicopter 10 in this second embodiment by the same equation as for the first embodiment, the angles .sub.d, .sub.g still being measured from the longitudinal direction X towards the thrust axis P.sub.d, P.sub.g as shown in FIGS. 6 and 7, and being considered to being positive in the counterclockwise direction.

[0098] Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.