Rotating wing blade of an aircraft, and an aircraft equipped with such a blade

Abstract

The present invention relates to a blade (20) for a rotating wing that rotates about an axis of rotation (AX), said blade (20) extending along the pitch axis (AXPAS) from a first end (51) to a second end (52), the blade (20) comprising a blade body (25) having, from the first end (51) to the second end (52), a succession of sections (S) substantially perpendicular to the pitch axis (AXPAS). The blade (20) has, along its pitch axis, sections having: increasing and then decreasing chords, a relative thickness that decreases from an initial section (SINI) to a final section (SF), twist angles that increase continuously from the original section (SO) to an initial section (SINI) and then decrease, and an evolving offset with respect to the pitch axis. (Shorthand figure: Figure 2)

Description

Title of the invention: rotating wing blade of an aircraft, and aircraft equipped with such a blade

[0001] The present invention relates to a rotating wing blade of an aircraft, as well as an aircraft having such a blade.

[0002] An aircraft may include a rotary wing equipped with at least one blade. The blade is, in particular, rotatable about the rotary wing's axis of rotation and its pitch axis. For example, each blade is connected to a pitch control system. Such a pitch control system may include actuators articulated to a lower swashplate of a swashplate assembly, an upper swashplate of this swashplate assembly being connected to each blade by a respective pitch rod. The pitch control system may further include an upper compass connecting the upper swashplate to a rotor mast and a lower compass connecting the lower swashplate to a stationary housing. Each blade may also be connected to at least one component sometimes called a "drag damper" or "frequency adapter."

[0003] Such a blade comprises, depending on its span, a blade root intended to be attached to a hub, and then an aerodynamic running portion. The running portion provides most of the lift of the blade

[0004] According to another aspect, a rotary-wing aircraft has the advantage of being able to operate with both high forward speeds and very low forward speeds, or even zero during a hovering phase.

[0005] The geometric characteristics of a blade do in fact have an impact on the operation of the aircraft during forward flights at high speeds and flights at low speeds.

[0006] Indeed, the higher the forward speed, the more the blades generate stresses on the pitch control system, and even on the frequency adapters or drag dampers. A manufacturer may seek to minimize these stresses.

[0007] In addition, a manufacturer seeks to obtain blades which enable interesting performance at low speeds, and in particular which enable takeoff with a maximized payload.

[0008] However, these two objectives seem antagonistic. Reducing the forces introduced at high forward speeds in the pitch control system, or even in the frequency adapters or drag dampers, can indeed be achieved by acting on the geometric characteristics of the blades, but generally at the expense of the performance achieved at low speeds, and vice versa.

[0009] The blades of a conventional helicopter, referred to as "conventional blades" for convenience thereafter, are then sized to generate acceptable forces in the pitch control system, or even in the frequency adapters or drag dampers, while allowing interesting performance to be achieved at low speeds.

[0010] However, some aircraft can operate at higher speeds in steady cruise, for example, exceeding 200 knots instead of the 150 knots generally observed for a typical helicopter. At 200 knots and above, a conventional rotor blade can introduce stresses in the pitch control system (actuators, pitch rods, swashplates, compasses, etc.), as well as in the frequency adapters or drag dampers, which may impact their service life.

[0011] Conventionally, a blade can be defined using the shape of the aerodynamic profiles of the blade sections and the positioning of these sections relative to each other. Thus, French patent FR 3045564 describes a blade for a rotary-wing aircraft rotor, the blade extending along a blade axis between a blade tip suitable for connection to a rotor hub and a blade tip. The blade comprises a profiled section located between the blade tip and the blade tip, the profiled section being made up of a succession of aerodynamic profiles. The blade tip is located at a reference distance equal to a rotor radius R from the axis of rotation. The chord of the profiles, defined as the distance between the leading edge and the trailing edge of said profiles, of the profiled section increases between the beginning of the profiled section and a first section located at a first distance from the axis of rotation A between 0.6*7 and 0.9*7?, the chord decreasing beyond the first section. The geometric twist of the blade section profiles decreases between a second section located at a second distance from the axis of rotation between 0.3*7? and 0.4*7? and the blade tip, a first twist gradient being between -25° per radius 7? and -4° per radius 7? between the second section and a third section located at a third distance from the axis of rotation A between 0.4*7? and 0.6*7?, a second twist gradient being between -25° per radius 7? and -4° per radius between the third section and a fourth section located at a fourth distance from the axis of rotation A between 0.65*7? and 0.85*7?, a third twist gradient being between -16° per radius 7? and -4° per radius 7? between the fourth section and a fifth section located at a fifth distance from the axis of rotation between 0.85*7? and 0.95*7?, a fourth twist gradient being between -16° per radius R and 0° per radius R between the fifth section and the blade tip.

[0012] The twisting of a blade consists of varying the angles of the sections relative to each other. The "twist angle" of a section is understood to be the angle The geometric angle formed between the chord line of this section and a line parallel to the chord line of a chosen reference section of this blade. For convenience, a positive angle is subsequently considered to correspond to a nose-up inclination of the section relative to the reference section. The evolution of twist angles with respect to the span of the blade is called the "twist law."

[0013] French patent FR 3045565 describes a blade for a rotary-wing aircraft rotor comprising a profiled section located between the blade root and the blade tip. The blade tip is located at a reference distance equal to a rotor radius R from the axis of rotation A. The chord of the profiles of the profiled section increases between the root of the profiled section and a first section located at a first distance from the axis of rotation of between 0.6*R and 0.9*R, the chord decreasing beyond the first section. The blade has a leading edge sweep between the root of the profiled section and a second section located at a second distance from the axis of rotation A of between 0.5*7* and 0.8*7*, the leading edge forming a first leading edge sweep angle al of between 0° and 10° with the blade axis. The blade has a forward-pointing arrow between the second section and a third section S3 located at a third distance from the axis of rotation between 0.6*7? and 0.95*7?, the leading edge forming a second leading-edge sweep angle a2 between 1° and 15° with the blade axis. In addition, the blade has a sweep directed towards the rear of the blade between the third section and the blade tip, the leading edge forming a third trailing-edge sweep angle a3 between -35° and -15° with the blade axis B.

[0014] The present invention aims to provide a blade limiting the forces introduced on a pitch control system, or even on at least a frequency adapter or a drag damper, at high speeds while allowing the generation of lift giving a rotary-wing aircraft acceptable performance at low speeds, and in particular in hovering, and for example performance at least substantially equivalent to the performance achieved on a conventional aircraft.

[0015] The present invention relates to a blade for a rotating wing of an aircraft, the blade being rotatable about an axis of rotation of the rotating wing and about a pitch axis, said blade extending along the pitch axis from a first end to a second end, the blade comprising a blade body having along the pitch axis a blade root and then a running portion formed by a succession of sections substantially perpendicular to the pitch axis, the blade body comprising along the pitch axis a blade root and then a running portion, the blade root being provided with an origin section forming the first end, the running portion extending along the pitch axis from an initial section to a final section forming the second end, the final section being located at a distance equal to a predetermined rotor radius R from said axis of rotation, each section extending along a transverse axis from a leading edge to a trailing edge separated by a maximum distance constituting a chord, each section of the blade body having a geometric twist angle with respect to a reference section located at a distance from the axis of rotation equal to 70% of the rotor radius R,

[0016] The blade also has the following characteristics:

[0017] - the initial section is disposed at a distance from the axis of rotation between 20% and 30% of the rotor radius R,

[0018] - according to a law of variation in span of the chord of the sections, the chord of sections increases from the original section up to a maximum chord reached in a first section located at a first distance from the axis of rotation between 75% and 80% of the rotor radius R, then decreases according to a law exhibiting on the one hand a slow decrease up to a second section and on the other hand a rapid decrease beyond the second section, the second section being located at a second distance from the axis of rotation between 80% and 95% of the rotor radius R, an average aerodynamic chord dimensionless by the rotor radius R being between 0.05 and 0.08, the maximum chord dimensionless by the rotor radius R being greater than the average aerodynamic chord dimensionless by the rotor radius R and between 0.06 and 0.1,

[0019] - according to a law of variation in span of relative thickness, the sections have a relative thickness which decreases from the original section to the initial section from a relative thickness between 0.25 and 0.70 up to a relative thickness between 0.12 and 0.15, the current part having from the initial section up to an intermediate section a constant relative thickness or a relative thickness which decreases then is constant, the current part having a relative thickness which decreases away from the intermediate section up to a relative thickness between 0.07 and 0.08 in the final section, the intermediate section being at a distance from the axis of rotation between 65% and 85% of the rotor radius R;

[0020] - according to a twisting law, the geometric twisting angles increase continuously from the original section to the initial section, from a minimum negative angle to a maximum positive angle, then decreasing according to a first gradient between -9° per rotor radius R and -13° per rotor radius R until a third section located at a distance from the axis of rotation between 70% and 80% of the rotor radius R, then according to a second gradient lower than the first gradient until a fourth section located at a distance from the axis of rotation between 88% and 90% of the rotor radius R, then according to a third gradient lower than the first gradient until the final section,

[0021] - according to an offset law, an offset distance separating the pitch axis from a line quarter of a chord for each section, starting from the leading edge, decreases from the original section up to the initial section, this offset distance being constant in the current part of the initial section to a break section then decreases, the break section being located at a distance from the axis of rotation between 80% and 95% of the rotor radius R; the offset distance can decrease from the break section according to a decreasing law of at least 2nd order, namely according to a function whose derivative and second derivative are also decreasing.

[0022] A blade is usually dimensioned according to the desired rotor radius. This rotor radius is indeed a characteristic classically associated with a blade. The length of the blade root can vary from one rotating wing to another in order to always have the same running portion and the same rotor radius, regardless of the dimensions of the rotating wing components carrying the blades.

[0023] Each section of the blade root may have a thick profile, namely having a relative thickness greater than 15% of its chord, and each section of the main part may have a thin aerodynamic profile, namely having a relative thickness less than or equal to 15% of its chord.

[0024] The average aerodynamic chord is defined according to a weighting on the square of the radius:

[0025] | cfry^lr t-aero __ 1 *U) R - R [' -7 L r~dr -

[0026] with c(r) the law of variation in span of the chord of the sections, r0 the distance separating the original section from the axis of rotation, R the rotor radius and r the distance separating a section from the axis of rotation.

[0027] The current section comprises an intermediate section extending from the blade root, then a tip. The tip begins, for example, at a distance from the axis of rotation equal to 80% of the rotor radius R. Therefore, the reduction of loads generated by the blade relies in particular on the chords, twists and offsets obtained in the intermediate section of the current section, while the hovering performance is obtained by the shape of the tip of the current section, the location of the highest speeds, particularly in hovering flight.

[0028] In particular, the twist angle is relatively refined in the intermediate section, allowing the wingtip more freedom to optimize the aircraft's hovering performance, which is penalized by this twist choice in the intermediate section. Furthermore, the chord law maximizes the blade area in the effective flight zone during forward flight, while reducing the chord in the reversal circle, which is naturally larger at high speeds than with conventional helicopters.

[0029] The synergy of the aforementioned characteristics makes it possible to obtain a blade that, on the one hand, generates reasonable forces on a pitch control system, or even on frequency adapters or drag dampers, and on the other hand to achieve acceptable performance at low speeds.

[0030] By way of illustration, such a blade provides performance substantially equivalent to a conventional blade at low speeds. The hover figure of merit obtained with such a blade is close to that of a conventional blade for a rotor thrust corresponding to the operational flight envelope. Furthermore, the forces generated by such a blade at very high speeds, for example at 220 knots, are on the order of the forces generated by a conventional blade at high speed, namely, for example, at 150 knots.

[0031] The blade according to the invention may further comprise one or more of the following characteristics.

[0032] Thus, the blade root may include profiles established according to the teachings of document EP 3501979 AL

[0033] According to a possibility compatible with the preceding ones, the current part may comprise a first profile from the initial section to an internal section located at a distance from the axis of rotation of between 30 and 35% of the rotor radius R, a second profile from the internal section to the intermediate section, which is located for example at a distance from the axis of rotation equal to 70% of the rotor radius R, the second profile from the intermediate section to a transition section, which is located for example at a distance from the axis of rotation equal to 90% of the rotor radius R, a third profile from the transition section to the final section, and a fourth profile in the final section.

[0034] The first profile, the second profile, the third profile, and the fourth profile are different, or may even be "OA" profiles known to a person skilled in the art. For example, the first profile may take the form of profile OA415, the second profile may take the form of profile OA312, the third profile may take the form of profile OA309, and the fourth profile may take the form of profile OA407.

[0035] According to a possibility compatible with the preceding ones, whatever the embodiment, the blade may comprise all of the following characteristics:

[0036] - the chord of the sections increases from the original section up to a chord maximum reached according to an average growth rate of 4.47%,

[0037] - the initial section has a relative thickness of 0.45, the current part presenting at starting from the initial section a relative thickness which decreases linearly from a value of 0.15 to 0.12 at the level of an internal section and then is constant up to the intermediate section, the intermediate section being located at a distance from the axis of rotation equal to 70% of the rotor radius R,

[0038] - the twist angles increase according to a convex law at the blade root, the The first gradient is equal to -10° per rotor radius R.

[0039] - the quarter chord line is located on the pitch axis at the level of the section originally, the dimensionless offset distance by the rotor radius R being equal to +0.041% of the rotor radius in a section going from the initial section to the breaking section, the quarter chord line of this section being located between the pitch axis and the leading edge of the sections of this section.

[0040] The synergy of the aforementioned characteristics makes it possible to obtain a blade capable of generating reasonable forces at high speeds on a pitch control system, or even on frequency adapters or drag dampers.

[0041] In addition, the blade may include the following characteristics:

[0042] - the initial section is disposed at a distance from the axis of rotation equal to 24% of the rotor radius R,

[0043] - the dimensionless mean aerodynamic chord by the rotor radius R is equal to 0.0651.

[0044] The following variants notably feature different salmon.

[0045] According to a first variant:

[0046] -the maximum dimensionless chord by the rotor radius R is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R,

[0047] - the second distance is equal to 87% of the rotor radius R, the decrease of the chord of the sections of the current part going from -2.85% to -18.16% at the level of the second section, the chord decreasing from the second section along a curve having an inflection point in an inflection section located at a distance from the axis of rotation equal to 94.5% of the rotor radius R, the slope of the curve at the inflection point being along a horizontal axis,

[0048] - the current part has a relative thickness that decreases linearly with distance from the intermediate section down to a relative thickness of 0.07 in the final section,

[0049] - the second gradient is equal to -7.3° per rotor radius R, the third gradient is equal to -20° per rotor radius R, the fourth section being located at a distance from the axis of rotation equal to 88% of the rotor radius R,

[0050] - the rupture section being located at a distance from the axis of rotation equal to 85% of the rotor radius R, the dimensionless offset distance by the rotor radius R being equal to 0.051 in the final section with a quarter chord point located between the pitch axis and the trailing edge, the dimensionless offset distance by the rotor radius R varying according to a hyperbolic tangent law from the rupture section to the final section.

[0051] For example, the said hyperbolic tangent law is defined by the equation: YAC(^ ) YAC^ YACo-YACnp r , / , r \ -t with «YAC» the offset distance, ■t»=—+ tanh W1 - ) I "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, " "YACtip" equals -0.051 multiplied by the rotor radius R, "YACo" equals 0.041 multiplied by the rotor radius R, "rD / R" equals 0.85, "k" equals 23.1.

[0052] In a stationary position, this first variant can provide a figure of merit that is substantially equivalent to, or even better than, that of a conventional constant-chord blade for a rotor thrust corresponding to the operational flight envelope. Furthermore, the figure of merit can decrease for thrusts higher than that of this conventional blade and higher than the operational requirement. This late decrease in the figure of merit offers the possibility of expanding the operational requirement, for example, in the context of an upgrade of the aircraft equipped with this blade. For example, this late decrease in the figure of merit can allow for an increase in the aircraft's mass.

[0053] According to a second variant:

[0054] -the maximum dimensionless chord by the rotor radius R is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R,

[0055] - the second distance is equal to 87% of the rotor radius R, the decrease going from -2.85% to -18.16% at the second section, the chord decreasing from the second section along a curve having an inflection point in an inflection section located at a distance from the axis of rotation equal to 94.5% of the rotor radius R, the slope of the curve at the inflection point being along an oblique axis,

[0056] - the current part having a relative thickness that decreases linearly in moving away from the intermediate section to a thickness equal to 0.08 of a section located at a distance from the axis of rotation equal to 90% of the rotor radius R up to and including the final section,

[0057] - the second gradient is equal to -7.3° per rotor radius R, the third gradient is equal to -20° per rotor radius R, the fourth section being located at a distance from the axis of rotation equal to 88% of the rotor radius R,

[0058] - the rupture section being located at a distance from the axis of rotation equal to 91.5% of the rotor radius R, the dimensionless offset distance by the rotor radius R being equal to 0.03384 in the final section with a quarter chord point located between the pitch axis and the trailing edge, the dimensionless offset distance by the rotor radius R varying according to a hyperbolic tangent law from the rupture section to the final section.

[0059] Optionally, said hyperbolic tangent law is defined by the equation: YAqj) _ YACtip YAQrYAQp if with “YAC” the offset distance, R ~ R + "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, "YACtip" equal to -0.03384 multiplied by the rotor radius R, "YAC0" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 31.

[0060] In stationary mode, this second variant allows us to obtain a figure of merit substantially identical to that of the first variant, but with a decline in the figure of merit earlier.

[0061] According to a third variant:

[0062] -the maximum dimensionless chord by the rotor radius is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R,

[0063] - the second distance is equal to 94.5% of the rotor radius R,

[0064] - the current part having a relative thickness that decreases linearly in moving away from the intermediate section until reaching a relative thickness of 0.07 in the final section,

[0065] - the second gradient is equal to -10° per rotor radius R, the third gradient is equal at -20° per rotor radius R, the fourth section being located at a distance from the axis of rotation equal to 88% of the rotor radius R,

[0066] - the rupture section being located at a distance from the axis of rotation equal to 85% of the rotor radius R, the dimensionless offset distance by the rotor radius R being equal to 0.051 in the final section with a quarter chord point located between the pitch axis and the trailing edge, the dimensionless offset distance by the rotor radius R varying according to a predetermined law from the break section to the final section.

[0067] Optionally, said predetermined law is defined by the equation: YAC(f) YAC„p AC0-fi exp[( sig ) ]-ACtjp R tanhjXl-^)] r 9, with tanh[qi-i)]4exp[(g) 2 ] "YAC" the offset distance, "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, "YACtip" equal to -0.051 multiplied by the rotor radius R, "YACo" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 23.1, "d" equal to -0.29% of the rotor radius R, "u" equal to 92.8% of the rotor radius R and "sig" equal to 3.7% of the rotor radius R.

[0068] In stationary flight, this third variant exhibits a reduced figure of merit compared to those of the first and second variants for a rotor thrust corresponding to the operational flight domain, but this figure of merit is maintained for thrusts greater than the operational requirement, which may offer the possibility of expanding this operational requirement, for example, in the context of an upgrade of the aircraft equipped with this blade.

[0069] According to a fourth variant:

[0070] -the maximum dimensionless chord by the rotor radius R is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R,

[0071] - the second distance is equal to 94.5% of the rotor radius R,

[0072] - the current part having a relative thickness that decreases linearly in moving away from the intermediate section until reaching a relative thickness of 0.07 in the final section,

[0073] - the second gradient is equal to -10° per rotor radius R, the third gradient is equal at -20° per rotor radius R, the fourth section being located at a distance from the axis of rotation equal to 88% of the rotor radius R,

[0074] - the rupture section being located at a distance from the axis of rotation equal to 94% of the rotor radius R, the dimensionless offset distance by the rotor radius R being equal to 0.03384 in the final section with a quarter chord point located between the pitch axis and the trailing edge, the dimensionless offset distance by the rotor radius R varying according to a predetermined law from the break section to the final section.

[0075] Optionally, said predetermined law is defined by the equation: YAC(i) YAQip YAC0-^ exp (s"g ) ]-YACtjp R tanh k( 1-^)] r with tanh[fc(l-£)]+^ exp[(g) ] "YAC" the offset distance, "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, "YACtip" equal to -0.03384 multiplied by the rotor radius R, "YACo" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 32, "d" equal to 0.15% of the rotor radius R, "u" equal to 95.5 of the rotor radius R and "sig" equal to 1.3% of the rotor radius R.

[0076] The fourth variant has similar performance to that of the third variant.

[0077] Whatever the embodiment, the current part may include, starting from the blade foot, an intermediate part followed by a wingtip, the wingtip having a zero dihedral angle with respect to the intermediate part.

[0078] A dihedral angle is an alternative possibility. The blade with dihedral can allow for more interesting hovering performance.

[0079] The invention also relates to a rotating wing equipped with a hub movable in rotation around an axis of rotation, the rotating wing comprising at least one blade according to the invention attached to the hub.

[0080] An aircraft may be equipped with such a rotary wing. The aircraft may include a pitch control system to control the pitch of each blade of the rotary wing.

[0081] The invention and its advantages will become apparent in more detail in the following description, with illustrative examples given by reference to the accompanying figures, which represent:

[0082] [Fig. 1], a partial diagram of a blade according to the invention arranged on a rotating wing of an aircraft,

[0083] [Fig. 2], a view of an example of a blade according to the invention,

[0084] [Fig. 3], a view illustrating the profiles of a blade according to the invention,

[0085] [Fig.4], a diagram showing the evolution of the chord of the blade sections of [Fig.2] dimensionless by the rotor radius,

[0086] the [Fig.5], a diagram showing the evolution of the relative thickness of the sections of the blade of the [Fig.2],

[0087] [Fig.6], a diagram showing the evolution of the twist angle of the blade sections of [Fig.2],

[0088] [Fig.7], a diagram illustrating the evolution of the offset of the blade sections of [Fig.2],

[0089] [Fig. 8], a view of an example of a blade according to the invention,

[0090] [Fig. 9], a diagram showing the evolution of the chord of the blade sections of the [Fig.8] dimensionless by the rotor radius,

[0091] the [Fig.10], a diagram showing the evolution of the relative thickness of the sections of the blade of the [Fig.8],

[0092] [Fig.1 1], a diagram illustrating the evolution of the offset of the blade sections of [Fig.8],

[0093] [Fig. 12], a view of an example of a blade according to the invention,

[0094] [Fig. 13], a diagram showing the evolution of the chord of the blade sections of the [Fig. 13] dimensionless by the rotor radius,

[0095] the [Fig. 14], a diagram showing the evolution of the twist angle of the blade sections of the [Fig. 13],

[0096] the [Fig. 15], a diagram illustrating the evolution of the offset of the blade sections of the [Fig. 13],

[0097] [Fig. 16], a view of an example of a blade according to the invention, and

[0098] the [Fig.17], a diagram illustrating the evolution of the offset of the blade sections of the [Fig.16].

[0099] Elements present in several separate figures are assigned one and the same reference.

[0100] Figure 1 schematically shows a blade 20 according to the invention. Each blade 20 is a constituent part of a rotating wing 10 of an aircraft 1.

[0101] Each blade 20 can be carried by a hub 11, for example via a sleeve 12. According to the given illustration, the blade 20 is fixed to a sleeve 12 articulated by a laminated stop 9 to the hub 11. The hub 11 is rotationally fixed to a rotor mast 13 which rotates the hub 11 and the blades 20 around an axis of rotation AX.

[0102] In addition, each blade 20 is also rotationally mobile, in particular around its own pitch axis AXPAS, or even around a drag axis. The pitch axis AXPAS extends substantially in a radial vertical plane relative to the axis of AX rotation. To control the blade pitch, aircraft 1 includes a pitch control system 2.

[0103] This pitch control system 2 comprises, for example, several actuators 6 articulated to a lower plate 5 of a conventional swashplate assembly. Each blade 20 is then articulated to a pitch connecting rod 3, the pitch connecting rods 3 also each being articulated to the upper plate 4 of the swashplate assembly. An upper compass 7 can be articulated to the rotor mast 13 and to the upper plate 4, a lower compass 8 being articulated to the lower plate 5 and to a fixed support of the aircraft 1.

[0104] The aircraft 1 may also include frequency adapters or drag dampers. Each frequency adapter or drag damper is articulated to a blade 20 and to an adjacent blade or to the hub 11.

[0105] A blade 20 according to the invention makes it possible to limit the forces exerted on the pitch control system 2 and on the frequency adapters or the drag dampers at very high forward speeds of the aircraft 1, while giving the aircraft usual performance at low speeds.

[0106] Figures 2 to 17 illustrate various examples of blades 20 according to the invention.

[0107] Regardless of the embodiment and with reference to [Fig.2] for example, a blade 20 extends along the pitch axis AXPAS, and away from the rotation axis AX, from a first end 51 to a second end 52. The distance separating the second end 52 from the rotation axis AX is called the rotor radius R.

[0108] In particular, the blade 20 comprises a blade body 25 which successively presents, along the pitch axis AXPAS and moving away from the axis of rotation AX, a blade root 30 and then a running portion 40. The blade root 30 has the first end 51 and can be fixed to the sleeve 11 as shown in the example. Conversely, the running portion 40 has the second end 52. The running portion 40 can be decomposed into an intermediate portion 41 extended by a tip 42, the intermediate portion 41 extending from the blade root 30 to a distance from the axis of rotation AX equal to 80% of the rotor radius R. The tip 42 can have zero dihedral with respect to the intermediate portion 4L

[0109] The blade body 25 consists of a succession of sections S substantially perpendicular to the pitch axis AXPAS. The reference S designates any section, the references SO, SF, SREF, SINI, SINT, SI, S2, S3, S4, S5, S6, SINF, SRUPT designating particular sections where necessary.

[0110] Thus, the blade root 30 extends from an origin section SO forming the first end 51 to the first section of the current portion 40, called the initial section SINI. The initial section SINI can be positioned at a distance from the axis of rotation AX between 20% and 30% of the rotor radius R, and favorably equal to 24% of the rotor radius R, according to the examples given. The rotor radius R can be a predetermined characteristic of a blade according to the invention, only the blade root having a length that varies from one rotor to another.

[0111] The current part 40 extends from this initial section SINI to a final section SF forming the second end 52. The current part 40 further comprises a reference section SREF located at a distance from the axis of rotation AX equal to 70% of the rotor radius R.

[0112] Each section S has an aerodynamic profile and extends along a transverse axis from a leading edge BA to a trailing edge BF separated by a distance constituting a chord C. Each section S also has:

[0113] - a relative thickness equal to the quotient of its maximum thickness T and its chord C,

[0114] - a geometric twist angle with respect to the SREF reference section,

[0115] - an offset distance YAC between the pitch axis AXPAS and the quarter line of rope.

[0116] Furthermore, each section S of the blade root 30 may have a thick airfoil and each section S of the main part 40 may have a thin airfoil. Such a thin airfoil has a relative thickness less than or equal to 0.15.

[0117] Fig. 3 illustrates examples of aerodynamic profiles.

[0118] The blade root 30 may have rounded profiles. For example, the blade root 30 may have a first profile PI from the original section SO to a section SOI, then a second profile P2 having a relatively smaller thickness up to the initial section SINI (not included). The blade root may, for example, have profiles established according to the teachings of document EP 3501979 AL

[0119] The current part 40 may include a first profile, for example of type OA415, from the initial section SINI inclusive to an internal section S5 not included, possibly located at a distance from the axis of rotation AX between 30 and 35% inclusive of the rotor radius R. The current part 40 may then include a second profile, for example of type OA312, from the internal section S5 included to the intermediate section SINT not included, this intermediate section SINT possibly being located at a distance from the axis of rotation AX equal, for example, to 70% of the rotor radius R.The current part 40 can then include the second profile of the intermediate section SINT included to a non-included transition section S6 which can be at a distance from the axis of rotation AX equal to 90% of the rotor radius R, then a third profile, for example of type OA309, from the included transition section S6 to the non-included final section SF, and a fourth profile for example of type OA407 in the final section SF.

[0120] Furthermore, [Fig.4] presents a diagram showing on the ordinate the chord C of the sections S dimensionless by the rotor radius R and on the abscissa the distance r separating each section from the axis of rotation AX dimensionless by the rotor radius R. This diagram thus presents the law of evolution of the chord of the blade 20.

[0121] Regardless of the embodiment, the chord C of the sections S increases from the initial section SO up to a maximum chord Cmax. This chord Cmax is reached in a first section SI located at a first distance from the axis of rotation AX between 75% and 80% inclusive of the rotor radius R. Subsequently, the chord C decreases according to a curve exhibiting, on the one hand, a slow decrease up to a second section S2, and on the other hand, a rapid decrease. The terms "slow decrease" and "rapid decrease" mean that the arithmetic mean of the gradients between two adjacent sections S between the first section SI and the second section S2 is less than the arithmetic mean of the gradients between two adjacent sections S between the second section S2 and the final section SF.

[0122] The second section S2 is positioned at a second distance from the axis of rotation AX between 80% and 95% inclusive of the rotor radius R.

[0123] It should be noted that the dimensionless mean aerodynamic chord Caero per rotor radius R is between 0.05 and 0.08 inclusive. Furthermore, the dimensionless maximum chord Cmax per rotor radius R is greater than this dimensionless mean aerodynamic chord Caero per rotor radius R, being between 0.06 and 0.1 inclusive.

[0124] In particular, the illustrated examples all have an average aerodynamic chord Caero dimensionless by the rotor radius R equal to 0.0651. According to another aspect, the chord of the sections S can increase from the chord corresponding to the original section SO up to the maximum chord Cmax by an average rate of increase of 4.47%.

[0125] The embodiment of [Fig. 2] exhibits a maximum dimensionless chord Cmax, defined by the rotor radius R, equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R. Furthermore, the second distance is equal to 87% of the rotor radius R. In addition, the chord decrease in sections S of the current portion 40 increases from -2.85% to -18.16% at the second section S2. The chord evolution law then presents an inflection point PINF in an inflection section SINF located at a third distance from the axis of rotation AX equal to 94.5% of the rotor radius R, the slope of the curve at the inflection point being along the horizontal axis AXH.

[0126] Furthermore, [Fig.5] presents a diagram showing on the ordinate the relative thickness T / C of the sections S and on the abscissa the distance r separating each section S from the dimensionless axis of rotation AX by the rotor radius R. This diagram thus presents the law of evolution of the relative thickness of the sections of the blade 20.

[0127] Regardless of the embodiment, the sections S have a relative thickness T / C that decreases from the initial section S0 to the initial section SINI, with a relative thickness T / C between 0.25 and 0.70 inclusive, down to a relative thickness T / C between 0.12 and 0.15 inclusive. The current section 40, from the initial section SINI to an intermediate section SINT, has a constant relative thickness T / C or a relative thickness T / C that decreases and then becomes constant, depending on the examples given. Furthermore, the current section 40 has a relative thickness T / C that decreases with distance from the intermediate section SINT, down to a relative thickness T / C between 0.07 and 0.08 inclusive in the final section, the intermediate section SINT being located at a distance from the axis of rotation AX between 65% and 85% inclusive of the rotor radius R.

[0128] In particular, the illustrated examples all have an initial section SINI with a relative thickness T / C of 0.45. The current portion 40 of these examples has, starting from the initial section SINI, a relative thickness T / C that decreases linearly from a value of 0.15 to a value of 0.12 reached at an internal section S5, located between 30 and 35% inclusive of the rotor radius R, and then a constant relative thickness T / C up to the intermediate section SINT. The intermediate section SINT is located at a distance from the axis of rotation AX equal to 70% of the rotor radius R.

[0129] The realization of [Fig.2] has on its side a current part 40 provided with a relative thickness T / C which decreases linearly away from the intermediate section SINT up to a relative thickness equal to 0.07 in the final section SF.

[0130] Furthermore, [Fig.6] presents a diagram showing on the ordinate the angle TETAG of geometric twist of the sections S and on the abscissa the distance r separating each section S from the dimensionless axis of rotation AX by the rotor radius R. This diagram thus presents the law of evolution of the twist of the blade 20.

[0131] Regardless of the embodiment, the geometric twist angles of the sections S increase continuously from the original section SO to the initial section SINI, from a minimum negative angle TETAGMIN to a maximum positive angle TETAGMAX. Then, the geometric twist angles of the sections decrease according to a first gradient GRAD1 between -9° per rotor radius R and -13° per rotor radius R inclusive, up to a third section S3 located at a distance from the axis of rotation AX between 70% and 80% inclusive of the rotor radius R, then according to a second gradient GRAD2 lower than the first gradient GRAD1 up to a fourth section S4 located at a distance from the axis of rotation AX between 88% and 90% inclusive of the rotor radius R, and finally according to a third gradient GRAD3 lower than the first gradient GRAD1 up to the final section SF.

[0132] In particular, the illustrated examples all exhibit twist angles which increase according to a convex law at the level of the blade root 30, and a first gradient GRAD1 equal to -10° per rotor radius R.

[0133] The realization of [Fig.2] has on its side a second gradient GRAD2 equal to -7.3° per rotor radius R, a third gradient GRAD3 equal to -20° per rotor radius R, a fourth section S4 being located at a distance from the axis of rotation AX equal to 88% of the rotor radius R.

[0134] Furthermore, [Fig.7] presents a diagram showing on the ordinate the offset distance of the dimensionless sections S by the rotor radius R and on the abscissa the distance r separating each section S from the axis of rotation AX dimensionless by the rotor radius R. This diagram thus presents the law of evolution of the offset of the sections S of the blade 20.

[0135] Regardless of the embodiment, in each section S, an offset distance separates the pitch axis AXPAS from a point Pt located at the quarter of the chord C of this section S from the leading edge B A. The points Pt of the sections S form a line called the quarter chord line by those skilled in the art.

[0136] This offset distance decreases from the original section SO to the initial section SINI, then remains constant in the current portion 40 from the initial section SINI to a rupture section SRUPT, and finally decreases to the final section. The rupture section SRUPT is located at a distance from the axis of rotation AX between 80% and 95% inclusive of the rotor radius R.

[0137] In particular, the illustrated examples all exhibit an offset distance at the origin section SO which is equal to one-quarter of the chord of that origin section SO. In other words, the pitch axis and the quarter-chord line coincide in the origin section SO.

[0138] Furthermore, the dimensionless offset distance by the rotor radius R is equal to +0.041% of the rotor radius R in a section going from the initial section SINI to the break section SRUPT, the quarter chord line of this section being located between the pitch axis AXPAS and the leading edge BA of this section.

[0139] The embodiment of [Fig. 2] has a rupture section SRUPT positioned at a distance from the axis of rotation AX equal to 85% of the rotor radius R. The dimensionless offset distance perpendicular to the rotor radius R is also equal to 0.051 in the final section SF with a quarter-chord point located between the pitch axis AXPAS and the trailing edge BF. The dimensionless offset distance perpendicular to the rotor radius R varies according to a hyperbolic tangent law from the rupture section SRUPT to the final section SF. This hyperbolic tangent law can take the following form:

[0140] YAC(i) YACtip YAC(1-YAC(ip f, r., with “YAC” the distance of R - R + R tanh[X 1-»] tanh L Æ < 1 “ “> 1 offset, "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, "YACtip" equal to -0.051 multiplied by the rotor radius R, "YACo" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 23.1.

[0141] The embodiments in figures 8 to 17 feature salmon 42 which differ from the embodiment in figures 2 to 7.

[0142] Figures 8 to 11 illustrate a first variant V1 which differs from the realization of [Fig.2] by its laws of variation of the chord C, of ​​the relative thickness and of the offset at the level of the salmon 42. The twist law is identical to the law of the realization of figures 2 to 7 described previously.

[0143] As with the embodiment of [Fig. 2] and with reference to [Fig. 9], for this first variant VI, the maximum dimensionless chord Cmax by the rotor radius R is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R. Furthermore, the second distance separating the second section S2 from the axis of rotation AX is equal to 87% of the rotor radius R. It should be noted that the decrease increases from -2.85% to -18.16% at the second section S2. The chord C decreases from the second section S2 along a curve having an inflection point PINF in an inflection section SINF located at a third distance from the axis of rotation AX equal to 94.5% of the rotor radius R, but the slope of the curve at the inflection point is along an oblique axis AXO instead of a horizontal axis for the blade of the [Fig.2].

[0144] With reference to [Fig. 10], the salmon 42 of the current part 40 has a relative thickness T / C which decreases linearly away from the intermediate section SINT up to a thickness equal to 0.08 at a section located at a distance from the axis of rotation equal to 90% of the rotor radius R, then remains constant up to and including the final section SF.

[0145] With reference to [Fig. 11], the rupture section SRUPT is located at a distance from the axis of rotation AX equal to 91.5% of the rotor radius R. The dimensionless offset distance perpendicular to the rotor radius R is equal to 0.03384 in the final section SF with a quarter-chord point located between the pitch axis AXPAS and the trailing edge BF. The dimensionless offset distance perpendicular to the rotor radius R varies according to a hyperbolic tangent law from the rupture section SRUPT to the final section SF. This hyperbolic tangent law can take the following form:

[0146] YAC(i.) YACiip YACo-YACtjp f. r, ■ with “Y AC” the distance of -r-=~r-+ stanhlm-g)] offset, "R" the rotor radius, "r" the radius separating the section concerned from the axis of rotation, "YACtiP" equal to -0.03384 multiplied by the rotor radius R, "YAC0" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 31.

[0147] Figures 12 to 15 illustrate a second variant V2 which differs from the embodiment of Figures 2 to 7 by its laws of chord variation, twist and offset at the salmon 42. The law of variation of the relative thickness is identical to the law of realization of figures 2 to 7 described previously.

[0148] With reference to [Fig. 13], as for the blades in Figures 2 to 11, the maximum dimensionless chord Cmax by the rotor radius R is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R. On the other hand, the second distance is equal to 94.5% of the rotor radius R.

[0149] With reference to [Fig. 14], the second variant V2 differs from the realization of figures 2 to 7 by having a second gradient GRAD2 equal to -10° per rotor radius R, a third gradient GRAD3 equal to -20° per rotor radius R, the fourth section S4 also being at a distance from the axis of rotation AX equal to 88% of the rotor radius R.

[0150] With reference to [Fig. 15], as with blade 20 in Figures 2 to 7, the SRUPT rupture section is located at a distance from the axis of rotation AX equal to 85% of the rotor radius R, the dimensionless offset distance per unit area of ​​the rotor radius R being equal to 0.051 in the final section SF with a quarter-chord point located between the pitch axis AXPAS and the trailing edge BF. However, the dimensionless offset distance per unit area of ​​the rotor radius R varies according to a predetermined law from the SRUPT rupture section to the final section SF. This predetermined law is: YACQ) YAC, YAC^ exfe^YAC, R tanh k( 1-^ )] , r ,,with tanh[t(li)] + fexp[(g) 2 ] "YAC" the offset distance, "R" the rotor radius, "r" the radius separating the relevant section from the axis of rotation, "YACtip" equal to -0.051 multiplied by the rotor radius R, "YACo" equal to 0.041 multiplied by the rotor radius R, "rD / R" equal to 0.85, "k" equal to 23.1, "d" equal to -0.29% of the rotor radius R, "u" equal to 92.8% of the rotor radius R and "sig" equal to 3.7% of the rotor radius R.

[0151] Figures 16 to 17 illustrate a third variant V3 which differs from the realization of figures 2 to 7 only by its offset law at the salmon 42.

[0152] Thus, this blade 20 has a maximum chord Cmax dimensionless by the rotor radius R equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R and the second distance being equal to 94.5% of the rotor radius R.

[0153] The current part 40 has a relative thickness T / C which decreases linearly away from the intermediate section SINT until a relative thickness T / C equal to 0.07 in the final section SF.

[0154] In addition, the second gradient GRAD2 is equal to -10° per rotor radius R, the third gradient GRAD3 is equal to -20° per rotor radius R, the fourth section S4 being located at a distance from the axis of rotation AX equal to 88% of the rotor radius R.

[0155] However, and with reference to [Fig. 17], the rupture section SRUPT is now located at a distance from the axis of rotation AX equal to 94% of the rotor radius R. The The dimensionless offset distance per rotor radius R is equal to 0.03384 in the final section SF with a quarter-chord point located between the pitch axis AXPAS and the trailing edge BF. Finally, the dimensionless offset distance per rotor radius R varies according to the following predetermined law from the rupture section SRUPT to the final section SF:

[0156] YAC(i) YAC^ R ~ R + YACü4 ex4(^)2]-YACtip R tanh X1-^ )] , r -, with tanh[*(li)Mexp[(t)2] "YAC" is the offset distance, "R" is the rotor radius, "r" is the radius separating the relevant section from the axis of rotation, "YACtip" is equal to -0.03384 multiplied by the rotor radius R, "YACo" is equal to 0.041 multiplied by the rotor radius R, "rD / R" is equal to 0.85, "k" is equal to at 32, "d" equal to 0.15% of the rotor radius R, "u" equal to 95.5 of the rotor radius R and "sig" equal to 1.3% of the rotor radius R.

[0157] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is, of course, conceivable to replace a described means with an equivalent means without departing from the scope of the present invention and the claims.

Claims

1. Demands A blade (20) for a rotating wing (10) of an aircraft (1), the blade (20) being rotatable about an axis of rotation (AX) of the rotating wing (10) and about a pitch axis (AXPAS), said blade (20) extending along the pitch axis (AXPAS) from a first end (51) to a second end (52), the blade (20) comprising a blade body (25) having, along the pitch axis (AXPAS), a blade root (30) and then a running portion formed by a succession of sections (S) substantially perpendicular to the pitch axis (AXPAS), the blade root (30) being provided with an origin section (SO) forming the first end (51), the running portion (40) extending along the pitch axis (AXPAS) from an initial section (SINI) to a final section (SF) forming the second end (52), the final section (SF) being located at a distance equal to a predetermined rotor radius (R) from said axis of rotation (AX),each section extending along a transverse axis from a leading edge (BA) to a trailing edge (BF) separated by a maximum distance constituting a chord (C), each section of the blade body (25) having a geometric twist angle with respect to a reference section (SREF) located at a distance from the axis of rotation equal to 70% of the rotor radius (R), characterized in that:, - The initial section (SINI) is positioned at a distance from the axis of rotation (AX) between 20% and 30% of the rotor radius (R). - The chord (C) of the sections increases from the initial section (SO) up to a maximum chord (Cmax) reached in a first section (SI) located at a first distance from the axis of rotation (AX) between 75% and 80% of the rotor radius (R), then decreases according to a law exhibiting, on the one hand, a slow decrease until a second section (S2), and on the other hand, a rapid decrease. The second section (S2) is located at a second distance from the axis of rotation (AX) between 80% and 95% of the rotor radius (R). An average aerodynamic chord (Caero), dimensionless by the rotor radius (R), is between 0.05 and 0.08, and the maximum chord (Cmax), dimensionless by the rotor radius (R), is greater than the chord. average aerodynamics (Caero) dimensionless by the rotor radius (R) and between 0.06 and 0.1,

2. - the sections have a relative thickness (T / C) which decreases from the original section (SO) to the initial section (SINI) from a relative thickness (T / C) between 0.25 and 0.70 up to a relative thickness (T / C) between 0.12 and 0.15, the current part (40) having from the initial section (SINI) up to an intermediate section (SINT) a constant relative thickness (T / C) or a relative thickness (T / C) which decreases and then is constant, the current part (40) having a relative thickness (T / C) which decreases away from the intermediate section (SINT) up to a relative thickness (T / C) between 0.07 and 0.08 in the final section, the intermediate section (SINT) being at a distance from the axis of rotation (AX) between 65% and 85% of the rotor radius (R); -these geometric twist angles increase continuously from the original section (SO) to the initial section (SINI) from a negative minimum angle (TETAGMIN) to a positive maximum angle (TETAGMAX), then decrease according to a first gradient (GRAD1) between -9° per rotor radius and -13° per rotor radius (R) until a third section (S3) located at a distance from the axis of rotation (AX) between 70% and 80% of the rotor radius (R), then according to a second gradient (GRAD2) lower than the first gradient (GRAD1) until a fourth section (S4) located at a distance from the axis of rotation (AX) between 88% and 90% of the rotor radius (R), then according to a third gradient (GRAD3) lower than the first gradient (GRAD1) until the final section (SF), - an offset distance (YAC) separating the pitch axis (AXPAS) of a quarter chord line for each section decreasing from the original section (SO) to the initial section (SINI),this offset distance being constant in the current part (40) of the initial section (SINI) to a rupture section (SRUPT) then decreases, the rupture section (SRUPT) being located at a distance from the axis of rotation (AX) between 80% and 95% of the rotor radius R., Blade according to claim 1, characterized in that the current portion (40) comprises a first profile from the initial section (SINI) to an internal section (S5) located at a distance from the axis of rotation (AX) of between 30 and 35% of the rotor radius R, a second profile from the internal section (S5) to the intermediate section (SINT), the second profile from the intermediate section (SINT) to a transition section (S6), a third profile of the transition section (S6) to the final section (SF), and a fourth profile in the final section (SF).

3. Blade according to any one of claims 1 to 2, characterized in that the blade has the following characteristics: - the chord of the sections increases from the original section (SO) up to a maximum chord (Cmax) reached by an average rate of increase of 4.47%, - the initial section (SINI) has a relative thickness (T / C) of 0.45, the current part (40) having from the initial section (SINI) a relative thickness (T / C) which decreases linearly from a value of 0.15 down to 0.12 at the level of an internal section (S5) then is constant up to the intermediate section (SINT), the intermediate section (SINT) being located at a distance from the axis of rotation (AX) equal to 70% of the rotor radius R, - the twist angles increase according to a convex law at the level of the blade root (30), the first gradient (GRAD1) is equal to -10° per rotor radius (R), - the quarter chord line is located on the pitch axis at the level of the original section (SO), the offset distance being equal to +0.041% of the rotor radius (R) in a section going from the initial section (SINI) to the break section (SRUPT), the quarter chord line of this section being located between the pitch axis (AXPAS) and the leading edge (BA) of this section.

4. Blade according to claim 3, characterized in that the blade has the following characteristics: - the initial section (SINI) is disposed at a distance from the axis of rotation (AX) equal to 24% of the rotor radius (R), - the mean aerodynamic chord (Caero) dimensionless by the rotor radius (R) is equal to 0.0651.

5. Blade according to any one of claims 1 to 4, characterized in that: - the maximum chord (Cmax) dimensionless by the rotor radius (R) is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R, - the second distance is equal to 87% of the rotor radius (R), the decrease in chord of the sections of the current part (40) going from -2.85% to -18.16% at the level of the second section (S2), the chord (C) decreasing from the second section (S2) according to a curve (Cl) having an inflection point (PINF) in an inflection section (SINF) located at a third distance from the axis of rotation (AX) equal to 94.5% of the rotor radius (R), the slope of the curve at the inflection point being along a horizontal axis (AXH), - the current part (40) has a relative thickness (T / C) which decreases linearly away from the intermediate section (SINT) up to a relative thickness equal to 0.07 in the final section (SF), - the second gradient (GRAD2) is equal to -7.3° per rotor radius (R), the third gradient (GRAD3) is equal to -20° per rotor radius (R), the fourth section (S4) being at a distance from the axis of rotation (AX) equal to 88% of the rotor radius (R), - the rupture section (SRUPT) being at a distance from the axis of rotation (AX) equal to 85% of the rotor radius (R), the dimensionless offset distance per rotor radius (R) being equal to 0.051 in the final section (SF) with a quarter chord point located between the pitch axis (AXPAS) and the trailing edge (BF), the dimensionless offset distance per rotor radius (R) varying according to a hyperbolic tangent law from the rupture section (SRUPT) to the final section (SF).

6. Blade according to claim 5, characterized in that said hyperbolic tangent law is defined by the equation: YACffl) YACtjp YAC0-YACtjP r . , with «Y AC » k -.....«.....+ «3 the offset distance, «R » the rotor radius, «r » the radius separating the section concerned from the axis of rotation, «YACtiP » equal to -0.051 multiplied by the rotor radius R, «YAC0 » equal to 0.041 multiplied by the rotor radius R, «rD / R » equal to 0.85, «k » equal to 23.

1.

7. A blade according to any one of claims 1 to 4, characterized in that: - the maximum chord (Cmax) dimensionless by the rotor radius is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius R, - the second distance is equal to 87% of the rotor radius (R), the decrease going from -2.85% to -18.16% at the second section (S2), the chord (C) decreasing from the second section (S2) along a curve having an inflection point (PINF) in an inflection section (SINF) located at a distance from the axis of rotation (AX) equal to 94.5% of the rotor radius (R), the slope of the curve at the inflection point being along an oblique axis (AXO), - the current section (40) having a relative thickness (T / C) that decreases linearly with respect to the intermediate section (SINT) up to a thickness equal to 0.08 of a section located at a distance from the axis of rotation equal to 90% of the rotor radius up to and including the final section (SF), - the second gradient (GRAD2) is equal to -7.3° per rotor radius (R), the third gradient (GRAD3) is equal to -20° per rotor radius (R), the fourth section (S4) being located at a distance from the axis of rotation (AX) equal to 88% of the rotor radius (R), - the section of rupture (SRUPT) located at a distance from the axis of rotation (AX) equal to 91.5% of the rotor radius (R), the dimensionless offset distance by the rotor radius (R) being equal to 0.03384 in the final section (SF) with a quarter chord point located between the pitch axis (AXPAS) and the trailing edge (BF), the dimensionless offset distance by the rotor radius (R) varying according to a hyperbolic tangent law from the rupture section (SRUPT) to the final section (SF).

8. Blade according to claim 7, characterized in that said hyperbolic tangent law is defined by the equation: YAC(g) ù AC^, YAC^ ACt,pr , r \ i with «YAC» the «-.....«.....+ offset distance, «R» the rotor radius, «r» the radius separating the section concerned from the axis of rotation, «YACtiP» equal to -0.03384 multiplied by the rotor radius R, «YAC0» equal to 0.041 multiplied by the rotor radius R, «rD / R» equal to 0.85, «k» equal to 31.

9. Blade according to any one of claims 1 to 4, characterized in that: - the maximum chord (Cmax) dimensionless by the rotor radius (R) is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius (R), - the second distance is equal to 94.5% of the rotor radius (R), - the current section (40) having a relative thickness (T / C) that decreases linearly with distance from the intermediate section (SINT) until reaching a relative thickness (T / C) of 0.07 in the final section (SF), - the second gradient (GRAD2) is equal to -10° per rotor radius (R), the third gradient (GRAD3) is equal to -20° per rotor radius (R), the fourth section (S4) being located at a distance from the axis of rotation (AX) equal to 88% of the rotor radius (R), - the rupture section (SRUPT) being located at a distance from the axis of rotation (AX) equal to 85% of the rotor radius (R), the dimensionless offset distance per rotor radius (R) being equal to 0.051 in the final section (SF) with a quarter-chord point located between the pitch axis (AXPAS) and the trailing edge (BF), the dimensionless offset distance per rotor radius (R) varying according to a predetermined law from the rupture section (SRUPT) to the final section (SF).

10. Blade according to claim 9, characterized in that said predetermined law is defined by the equation: YAC® YACap YAC^ exp^YAC,,, dr 2]with R - R + tanh l M1 ' R ) 1 + R CXP [ 1^g ) J «YAC» the offset distance, «R» the rotor radius, «r» the radius separating the section concerned from the axis of rotation, «YACtiP» equal to -0.051 multiplied by the rotor radius R, «YAC0» equal to 0.041 multiplied by the rotor radius R, «rD / R» equal to 0.85, «k» equal to 23.1, «d» equal to -0.29% of the rotor radius R, «u» equal to 92.8% of the rotor radius R and «sig» equal to 3.7% of the rotor radius R.

11. Blade according to any one of claims 1 to 4, characterized in that: - the maximum chord (Cmax) dimensionless by the rotor radius (R) is equal to 0.0746, the first distance being equal to 78.2% of the rotor radius (R), - the second distance is equal to 94.5% of the rotor radius (R), - the current part (40) having a relative thickness (T / C) which decreases linearly away from the intermediate section (SINT) up to a relative thickness (T / C) equal to 0.07 in the final section (SF), - the second gradient (GRAD2) is equal to -10° per rotor radius (R), the third gradient (GRAD3) is equal to -20° per rotor radius (R), the fourth section (S4) being located at a distance from the axis of rotation (AX) equal to 88% of the rotor radius (R), - the break section (SRUPT) being located at a distance from the axis of rotation (AX) equal to 94% of the rotor radius (R), the dimensionless offset distance per rotor radius (R) being equal to 0.03384 in the final section (SF) with a quarter chord point located between the pitch axis (AXPAS) and the trailing edge (BF), the dimensionless offset distance per rotor radius (R) varying according to a predetermined law from the break section (SRUPT) to the final section (SF).

12. Blade according to claim 11, characterized in that said predetermined law is defined by the equation: .10¾.) _ tanhlÆf 1 - ) 1 +- exof (—)2]aVeC R ~ R + ru,^0-¾)] JJ+k exP[w JJ «YAC» the offset distance, «R» the rotor radius, «r» the radius separating the relevant section from the axis of rotation, «YACtiP» equal to -0.03384 multiplied by the rotor radius R, «YAC0» equal to 0.041 multiplied by the rotor radius R, «rD / R» equal to 0.85, «k» equal to 32, «d» equal to 0.15% of the rotor radius R, «u» equal to 95.5 of the rotor radius R and «sig» equal to 1.3% of the rotor radius R.

13. Blade according to any one of claims 1 to 12, characterized in that the running part (40) comprises, starting from the blade foot (30), an intermediate part (41) followed by a wingtip (42), the wingtip (42) having a zero dihedral with respect to the intermediate part (41).

14. Rotating wing (10) provided with a hub (11) movable in rotation about an axis of rotation (AX), the rotating wing (10) comprising at least one blade (20) attached to the hub (11), characterized in that said blade (20) is according to any one of claims 1 to 13.

15. Aircraft (1) equipped with a rotary wing (10), characterized in that said rotary wing is according to claim 14.

Images