Rotorcraft with tail propeller with shroud

Abstract

The invention relates to a rotary-wing aircraft (100) extending between a head (101) and a tail (102) along an associated roll axis R. The rotary-wing aircraft (100) comprises a main rotor (120), a propeller (130) configured at least to push the rotary-wing aircraft (100) in a forward flight state, wherein the propeller (130) forms a circular propeller disc when rotating around an associated rotation axis, and a shrouded duct (140) arranged in the tail (102) and forming an internal air duct at least partially housing the propeller (130), wherein the shrouded duct (140) comprises a yaw and pitch stability enhancement unit to increase the yaw and pitch stability of the rotary-wing aircraft (100) in the forward flight state.

Description

TECHNICAL FIELD

[0001] The invention relates to a rotary wing aircraft which extends along an associated roll axis between a head and a tail and comprises a fuselage having a front and a rear, wherein the rotary wing aircraft further comprises a main rotor configured at least to provide lift in a hovering state of the rotary wing aircraft, a propeller configured at least to push the rotary wing aircraft in a forward flight direction in a forward flight state, and a shrouded duct arranged in the tail and forming an internal air duct at least partially accommodating the propeller. BACKGROUND

[0002] One example of a rotary wing aircraft having a main rotor and a propeller is the so-called compound helicopter. In such a compound helicopter, the main rotor is basically responsible for the lifting work, but is usually also responsible for the pushing work in a forward flight state of the compound helicopter at least at lower or medium forward speeds. The propeller is in turn arranged mainly to disengage the main rotor from its pushing work at higher forward speeds in the forward flight state and can make the compound helicopter advance at a relatively high forward speed which cannot be achieved using the main rotor alone.

[0003] However, in operation, the main rotor generates a torque about the yaw axis of the compound helicopter. This torque has to be counteracted by suitable counter torque means to ensure the required yaw stability of the compound helicopter in flight operation.

[0004] Document US 4,928,907 describes a compound helicopter having a main rotor, a tail boom and a tail propeller mounted on the tail of the tail boom, wherein the tail propeller is used only to provide forward thrust during aircraft mode flight when the main rotor can be pitch to a no-lift attitude and during the transition from helicopter vertical flight to forward flight in aircraft mode. The required counter torque balancing force during hovering mode is formed by the force of ailerons which are differentially controlled when the respective wing is vertically aligned with the downwash of the main rotor. Furthermore, a vertically movable horizontal airfoil is arranged on the tail boom, which has a controllable mechanism which can provide a counter torque reaction force during hovering mode by the downwash of the main rotor.

[0005] Document EP 1 395 489 A2 describes a compound helicopter having a main rotor, a tail propeller and a tail boom. The tail boom forms a plenum chamber connected with an associated linear jet. The associated linear jet is fixedly coupled to the tail boom and is adapted to release a sheet of fluid formed by pressurized air in the plenum chamber in a direction substantially tangent to the outer surface of the tail boom to divert the downwash flow of the main rotor and thereby generate a force that counteracts the offset torque generated by the main rotor. The pressurized air is provided by a fan or by directing exhaust gases from the engine of the compound helicopter into the plenum chamber. The compound helicopter further comprises a yaw control member that is movably coupled to the tail boom and that can be selectively positioned based on input from a pilot.

[0006] Document EP 2 511 177 A1 describes a compound helicopter having a main rotor, a tail propeller and a tail boom surrounded by an oar. The oar has individual blades that are substantially parallel to the longitudinal axis of the tail boom. In operation, the oar is driven to provide a counter torque that counteracts the offset torque generated by the main rotor.

[0007] However, the above counter torque devices for compound helicopters having a main rotor and a propeller are generally complex and require delicate components, such as differentially controlled ailerons or movable airfoils, additional fans or oars. These actuatable components increase the overall system complexity and the overall weight of these counter torque devices.

[0008] Document US 3,241,791 describes a compound helicopter having a main rotor and a tail propeller. The tail propeller is mounted on a circular shroud attached to the fuselage of the compound helicopter. The circular shroud is further provided with a rudder that is pivotally mounted on the circular shroud downstream of the tail propeller. In operation, the tail propeller generates an air flow that is directed through the circular shroud towards the rudder and can be deflected by the rudder to counteract the torque generated by the main rotor.

[0009] Documents US 3,083,935 A1 and DE 1 456 063 A1 describe a similar compound helicopter having a main rotor and a tail propeller housed in a circular shroud provided with a rudder. In addition to the rudder, a pitch trim tab is provided. The pitch trim tab is provided for improving the pitch control of the compound helicopter.

[0010] The documents US 5,131,603, US 2010 / 0324758 Al and US 2011 / 0036954 Al describe a similar compound helicopter having a main rotor and a tail propeller housed in a circular shroud provided with a rudder and a pitch trim tab. In addition, one or more deployable cap vanes are provided in addition to the rudder and the pitch trim tab. The deployable cap vanes are deployable from the circular shroud and are arranged to deflect the tail propeller thrust in the deployed state.

[0011] The document US 5,277,381 describes a similar compound helicopter having a main rotor and a tail propeller housed in a circular shroud provided with a rudder and a pitch trim tab. In addition, a pivoting side wall flap is provided in addition to the rudder and the pitch trim tab. The pivoting side wall flap is pivotally mounted on the circular shroud and is arranged to deflect the tail propeller thrust in the pivoted state.

[0012] The documents US 3,260,482 and DE 1481629 Al also describe a compound helicopter having a main rotor and a tail propeller housed in a circular shroud. The circular shroud is provided with a plurality of vertically positioned directional control vanes and a horizontally positioned pitch trim tab. In operation, the tail propeller generates an airflow which is directed through the circular shroud towards the plurality of vertically positioned directional control vanes. The airflow can be deflected by the vertically positioned directional control vanes, thereby counteracting the torque generated by the main rotor.

[0013] The document DE 1456063 Al describes a rotary wing aircraft having two horizontally positioned main rotors spaced apart in the direction of the roll axis of the aircraft and housed in associated circular shrouds provided with pivotable control flaps. The pivotable control flaps are arranged parallel to the roll axis of the aircraft and are pivotable to counteract the torque generated by the two horizontally positioned main rotors.

[0014] Further aircraft having circular shrouds provided with rudders, flaps, vanes or tabs and the like are known from the prior art. For example, the document US 2,929,580 describes a propeller aircraft having two propellers housed in associated circular shrouds provided with horizontally arranged flaps. However, these horizontally arranged flaps are not used for anti-torque control compared to the above described anti-torque devices. EP 3251952 and DE 4119388 are also known.

[0015] However, all of the above described anti-torque devices having rudders, flaps or vanes for anti-torque control mainly have an impact in the hovering state of the respective compound helicopter or rotary wing aircraft, however their aerodynamic efficiency in the transition and forward flight state is limited. SUMMARY

[0016] It is therefore an object of the present application to provide a new type of compound helicopter, in general a new type of rotary wing aircraft having a main rotor and a tail propeller, which is equipped with an improved anti-torque device having a minimum loss of thrust and a minimum increase of drag due to control inputs and means.

[0017] This object is achieved by a rotary wing aircraft having a main rotor and a tail propeller, comprising the features of claim 1. More specifically, according to the present application, there is provided a rotary wing aircraft extending between a head and a tail along an associated roll axis and comprising a fuselage having a front and a rear. The rotary wing aircraft comprises a main rotor configured at least to provide lift in a hover state of the rotary wing aircraft, a propeller configured at least to push the rotary wing aircraft in a forward flight direction in a forward flight state, and a shrouded duct arranged in the tail and forming an inner air duct at least partially housing the propeller. The rear extends between the front and the shrouded duct and comprises an asymmetric cross-sectional profile in the direction of the associated roll axis. The rear is configured to generate lateral thrust for main rotor anti-torque by main rotor downwash. The propeller comprises a predetermined number of propeller blades forming a circular propeller disc when the propeller is rotated around an associated rotation axis. The shrouded duct comprises yaw and pitch stability augmentation units to increase yaw and pitch stability of the rotary wing aircraft in the forward flight state.

[0018] Thus, the inventive rotary wing aircraft can advantageously be controlled with increased aerodynamic efficiency at least in the transition and forward flight states, in particular with a minimum loss of thrust and a minimum increase of drag due to control inputs and means. More specifically, by implementing the yaw and pitch stability augmentation units as fixed and movable means in the front and rear of the shrouded duct, the take-off (pitch) characteristics of the rotary wing aircraft can be controlled and its main rotor torque can be balanced in a way having aerodynamic efficiency. Thus, an increased take-off performance can be achieved, in particular in the forward flight state.

[0019] Preferably, the shrouded duct has a specific shape and is shaped, for example, in terms of a non-circular cross-section, variable length, different angles of attack, varying distance of the leading / trailing edges with respect to the associated propeller blade plane, etc. This specific shape and shaping advantageously enables the shrouded duct to generate lateral thrust for main rotor anti-torque in the transition and forward flight states of the rotary wing aircraft.

[0020] Furthermore, additional lateral thrust against the counter torque of the main rotor can be generated by means of the main rotor downwash by at least one asymmetric source. For example, the at least one asymmetric source can be positioned on the side of the rotor blades of the main rotor of the rotary-wing aircraft that is closest to the approach in the case of a rotation of the main rotor. In other words, if the main rotor rotates in a counterclockwise direction, the at least one asymmetric source is positioned on the starboard side, i.e. the right side, of the fuselage of the rotary-wing aircraft, which is preferably formed as a rotary-wing aircraft with a main rotor and a propeller.

[0021] By way of example, the at least one asymmetric source can be formed as a flange of the fuselage, which can be provided close to the lower side of the fuselage. Such a flange can be formed to be sufficiently large so that it can be used as a step. Furthermore, it can be integrated into an aerodynamically shaped ski landing gear, for example. Alternatively, such a flange can be configured by means of a cover of a telescopic head landing gear. In this case, the aerodynamic properties of the rotary-wing aircraft when flying fast forward will not be affected by the flange, since it will be retracted into the fuselage together with the telescopic head landing gear, so that the overall configuration again has good aerodynamic properties. In fact, the use of the flange to generate the corresponding counter torque preferably takes place mainly in the hovering state and slow forward flight.

[0022] The at least one asymmetric source can also comprise an elongation, i.e. a convex protrusion, on the top of the fuselage of the rotary-wing aircraft, i.e. on the upper side of the fuselage. For example, a suitable elongation can be obtained by suitably shaping an upper fairing that covers the upper deck of the rotary-wing aircraft. The highest point of the upper fairing can be moved to the opposite side of the fuselage, so that there is a smooth transition here, with a constant tangent in at least the upper region of the cross section.

[0023] The lateral thrust against the counter torque of the main rotor that can be generated by means of the shrouded duct and / or the at least one asymmetric source can advantageously be increased by means of the lateral thrust from the main rotor downwash that is generated by means of the rear of the fuselage of the rotary-wing aircraft. More particularly, the rear preferably generates the main part of the lateral thrust from the main rotor downwash. Thus, the rear of the fuselage of the rotary-wing aircraft can exhibit a shape similar to the profile of a so-called high-lift airfoil, so that a relatively high lateral thrust can already be generated at relatively low downwash speeds. Preferably, at least the main part of the rear of the fuselage is positioned asymmetrically on the side of the rotor blades of the main rotor of the rotary-wing aircraft that is more distantly approached in the case of a rotation of the main rotor. In other words, if the main rotor rotates in a counterclockwise direction, the main part of the rear of the fuselage is positioned on the starboard side of the rotary-wing aircraft.

[0024] Preferably, the vertical cut through the rear of the fuselage at a position close to the tail of the rotary wing aircraft resembles a high-lift airfoil. Such a high-lift airfoil, which is preferably oriented at least substantially in vertical direction at this position, provides a "lift", i.e. a lateral thrust in the same direction as the main rotor rotates. In other words, if the main rotor rotates in a counter-clockwise direction, the lateral thrust points in this direction as well.

[0025] Therefore, less power is required in hover, since the downwash drag generated in response to the main rotor downwash is reduced due to the conversion of the main rotor downwash into lateral thrust compared to the downwash drag generated in response to the main rotor downwash in a conventional tail boom. Therefore, a lift capacity gain and a fuel saving can be achieved.

[0026] Advantageously, a transition from the cross-sectional profile of the fuselage of the rotary wing aircraft, which resembles the cross-sectional profile of a conventional helicopter and can be symmetrical, to the high-lift airfoil shaped cross-sectional profile of the rear of the fuselage can be implemented as a smooth concave section in the region of the main rotor, preferably in the region between the main rotor and the rear of the fuselage. The latter is preferably shaped for avoiding airflow separation.

[0027] In an illustrative implementation, the rear is provided with a shrouded duct in the tail, in which a propeller is rotatably mounted. The base transition of the rear of the fuselage to the shrouded duct is preferably smooth, such that the rear of the fuselage at least substantially has a shape corresponding to a quarter of the shrouded duct.

[0028] Furthermore, at least one wing-like aerodynamic device, which is also referred to as "support wing" in the following, can be associated with the rear of the fuselage for additionally generating a lateral thrust for the main rotor counter torque by the main rotor downwash. In the operation of the rotary wing aircraft, there is a certain amount of main rotor downwash, mainly in hover. Therefore, a "lift" in horizontal direction, i.e. a lateral thrust, can advantageously be generated simultaneously by the main rotor downwash via the rear of the fuselage, the associated support wing and the front and shrouded duct, thereby counteracting the torque generated by the main rotor in hover.

[0029] Preferably, the support wing is mainly vertically oriented. More specifically, the support wing can connect the upper deck of the rotary wing aircraft to the shrouded duct, e.g. from a position slightly behind the main rotor to the shrouded duct. Advantageously, the support wing also exhibits a shape similar to the profile of a high-lift airfoil. Preferably, the maximum width of the support wing is located at a region between 60% of the length of the rotor blades of the main rotor and the outer end of the rotor blades.

[0030] Advantageously, the support wings and the rear of the fuselage support the shrouded duct on both sides of the rotary wing aircraft, as there is no central portion of the rear of the fuselage compared to a conventional tail boom. Preferably, the tail propeller drive shaft is arranged between the support wings and the rear of the fuselage. This tail propeller drive shaft can also generate a lateral thrust by the so-called Magnus effect, which occurs when a cylinder or cone is rotated in a flow oriented perpendicular to its axis of rotation.

[0031] Preferably, the tail propeller drive shaft is rotatably mounted on the shrouded duct by means of bearings supported by a predetermined number of fixed profiles provided, for example, three fixed profiles. Preferably, the fixed profiles are mounted on the shrouded duct near the upper and lower edges of the rear of the fuselage at the respective positions of the support wings and the positions connecting them to the shrouded duct.

[0032] Alternatively, in addition to the provision of the tail propeller drive shaft, the tail propeller can also be driven independently of the main rotor, for example by a separate engine. This separate engine can be of a different type than the respective main engines driving the main rotor, thus enabling an engine mix with high redundancy, as the rotary wing aircraft can be operated by each engine independently of the others when flying forward.

[0033] According to some aspects, the yaw and pitch stability enhancement unit comprises a rudder arranged downstream of the circular propeller disc in the forward flight direction, the rudder comprising an elongated rudder body twisted around a length axis of the elongated rudder body.

[0034] According to some aspects, the elongated rudder body comprises a leading edge provided with a plurality of spaced-apart nodules.

[0035] According to some aspects, the elongated rudder body comprises an airfoil-shaped profile having a straight central line rotating around a length axis of the elongated rudder body between two axial ends of the elongated rudder body, or having an arcuate central line comprising varying curvature between two axial ends of the elongated rudder body.

[0036] According to some aspects, the rudder is rotatably mounted on the shrouded duct or is provided with one or more rotating flaps.

[0037] According to some aspects, the yaw and pitch stability enhancement unit comprises at least one strut arranged downstream of the circular propeller disc in the forward flight direction, the at least one strut comprising an elongated strut body twisted around a length axis of the elongated strut body.

[0038] According to some aspects, the elongated strut body comprises a leading edge provided with a plurality of spaced-apart nodules.

[0039] According to some aspects, the elongated strut body comprises a wing profile shape contour having a straight center line rotating between the two axial ends of the elongated strut body around a length axis of the elongated strut body or having an arcuate center line comprising a varying curvature between the two axial ends of the elongated strut body.

[0040] According to some aspects, the yaw and pitch stability enhancement unit comprises at least one gull wing.

[0041] According to some aspects, the shrouded duct comprises a ring-shaped duct body and wherein the at least one gull wing is at least partially retractable into the ring-shaped duct body.

[0042] According to some aspects, the at least one gull wing is arranged on a trailing edge of the shrouded duct.

[0043] According to some aspects, the at least one gull wing at least partially forms a trailing edge of the shrouded duct in the neutral position.

[0044] According to some aspects, the yaw and pitch stability enhancement unit comprises a plurality of wing profile shape aerodynamic devices, in particular high-lift airfoils, which are arranged at least substantially parallel to the associated roll axis or are inclined with respect to the roll axis (R) in a range of + / - 10 degrees and form a transition from the rear portion to a leading edge of the shrouded duct.

[0045] According to some aspects, the shrouded duct comprises a leading edge which is arranged with a plurality of spaced-apart nodules.

[0046] According to some aspects, the rear portion comprises at least one wing profile shape aerodynamic device extending from the front portion to the tail portion, wherein the at least one wing profile shape aerodynamic device is configured to generate a lateral thrust for counteracting a torque of the main rotor by a downwash of the main rotor.

[0047] In the following description, preferred embodiments of the present application are outlined by way of example with reference to the accompanying drawings. In these drawings, identical or similar parts and elements are marked with the same reference numerals and letters and are therefore described only once in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 a perspective view of a rotary wing aircraft having a shrouded duct according to the present application is shown;

[0049] Figure 2 a side view of a rotary wing aircraft of Figure 1 is shown;

[0050] Figure 3 a top view of a rotary wing aircraft of Figure 1 and Figure 2 is shown;

[0051] Figure 4 Another perspective view of the rotary wing aircraft of Figures 1 to 3 is shown with an illustrative asymmetric source;

[0052] Figure 5 A side view of an illustrative propeller drive shaft of the rotary wing aircraft according to one aspect is shown; Figures 1 to 4

[0053] A side view of an illustrative propeller drive shaft of the rotary wing aircraft according to another aspect is shown; Figure 6 Figures 1 to 4 A functional diagram of the propeller drive shaft of

[0054] and Figure 7 is shown; Figure 5 Figure 6 A rear view of the shrouded duct of is shown with a yaw and pitch stability augmentation unit according to a first embodiment;

[0055] Figure 8A A perspective view of the shrouded duct of Figures 1 to 4 with a yaw and pitch stability augmentation unit is shown;

[0056] Figure 8B A perspective view of the shrouded duct of Figure 8A with a yaw and pitch stability augmentation unit is shown;

[0057] Figure 9A and Figure 9B A cross-sectional view of the rudder and horizontal strut of the yaw and pitch stability augmentation unit in different positions relative to the shrouded duct of Figure 8A and Figure 8B is shown;

[0058] Figure 10A and Figure 10B A cross-sectional view of a variation of the rudder and horizontal strut of the yaw and pitch stability augmentation unit of Figure 8A and Figure 8B is shown;

[0059] Figure 11 A perspective view of the shrouded duct of Figures 1 to 4 with a yaw and pitch stability augmentation unit according to a second embodiment is shown;

[0060] Figure 12A A cross-sectional view of the shrouded duct of Figure 11 along a tangent XIIA-XIIA of Figure 11 is shown;

[0061] Figure 12B A cross-sectional view of the shrouded duct of Figure 11 along a tangent XIIA-XIIA of Figure 11a sectional view along the tangent XIIB-XIIB;

[0062] Figure 13A and Figure 13B a sectional view along the tangent XIIB-XIIB; Figure 12B a sectional view along the tangent XIIB-XIIB;

[0063] Figures 14A to 15B a sectional view along the tangent XIIB-XIIB; Figure 12B a sectional view along the tangent XIIB-XIIB;

[0064] Figure 16 a sectional view along the tangent XIIB-XIIB; Figures 1 to 4 a sectional view along the tangent XIIB-XIIB;

[0065] Figures 17 to 18B a sectional view along the tangent XIIB-XIIB; Figures 1 to 4 a sectional view along the tangent XIIB-XIIB;

[0066] Figures 19A to 23 a sectional view along the tangent XIIB-XIIB; Figures 1 to 4 a sectional view along the tangent XIIB-XIIB. DETAILED DESCRIPTION

[0067] Figure 1 An illustrative rotary wing aircraft 100 is shown having a fuselage 110 and a main rotor 120. By way of example, the rotary wing aircraft 100 is represented with three mutually orthogonal axes P, R and Y. Axis P represents a lateral axis corresponding to a pitch axis inherent to the rotary wing aircraft 100, axis R represents a longitudinal axis corresponding to a roll axis inherent to the rotary wing aircraft 100, and axis Y represents a vertical axis corresponding to a yaw axis inherent to the rotary wing aircraft 100.

[0068] By way of example, the rotary wing aircraft 100 is represented in a forward flight state. Accordingly, only the components required in the forward flight state are shown in more detail, while the illustration of other components is omitted in order to keep the drawing simple and clear. For example, the fuselage 110 is not shown in more detail, e.g. in order to represent the respective doors and windows, nor are possible landing gears shown, which can be wheel landing gears or skid landing gears mounted on the fuselage 110, etc.

[0069] Illustratively, the fuselage 110 extends along the roll axis R from a head portion 101 to a tail portion 102 of the rotary wing aircraft 110. The fuselage 110 comprises a front portion 112 and a rear portion 114. Illustratively, the front portion 112 comprises a port side wall 103 and a starboard side wall 104. Preferably, the rear portion 114 extends as an extension of one of the port side wall 103 and the starboard side wall 104.

[0070] More specifically, the rear portion 114 preferably extends as an extension of the right side of the fuselage 110, which is further away from the rotor blades of the main rotor 120 in case of a rotation of the main rotor 120. Assuming that the main rotor 120 rotates in a counter clockwise direction, the rear portion 114 of the fuselage 110 is located on the starboard side of the rotary wing aircraft 100 and thus is provided as an extension of the right side wall 104 as shown.

[0071] By way of example, the front portion 112 merges into the rear portion 114 at an associated transition or recessed area 115. In other words, proceeding along the roll axis R from the head 101 of the fuselage 110, the fuselage 110 merges the front portion 112 into the rear portion 114 at the transition or recessed area 115, which in turn terminates in the tail 102.

[0072] The front portion 112 preferably forms a cabin 111 for passengers and / or cargo. The cabin 111, more generally the fuselage 110, illustratively extends in the direction of the yaw axis Y from the lower side 106 to an upper side 116, which separates the cabin 111 from an upper deck 105. The upper deck 105 is preferably covered by a cowling 118. By way of example, the cowling 118 can cover one or more suitable engines and a main gearbox that cause the main rotor 120 to rotate in operation. Thus, the main rotor 120 is rotatably mounted at the front portion 112 of the fuselage 110.

[0073] Preferably, the main rotor 120 is at least configured to provide lift in a hover state of the rotary wing aircraft 100. By way of example, the main rotor 120 forms a single rotor plane 122 and is adapted to provide lift and forward or backward thrust during operation. Illustratively, the main rotor 120 is implemented as a multi-bladed main rotor having a plurality of rotor blades 125, 126, 127, 128, 129, which are coupled to a rotor main shaft 124 at an associated rotor hub 123, which rotates about an associated rotor axis in operation of the rotary wing aircraft 100.

[0074] According to one aspect, the rotary wing aircraft 100 is implemented as a compound helicopter having a propeller 130 that is at least configured to push the rotary wing aircraft 100 in a forward flight direction 199 in a forward flight state. Thus, the rotary wing aircraft 100 is hereinafter referred to as "compound helicopter 100" for simplicity and clarity.

[0075] Illustratively, the propeller 130 includes a predetermined number of propeller blades 132 that form a circular propeller disc 135 when the propeller 130 is rotated about the associated axis of rotation 139. More specifically, the propeller blades 132 are rotated in operation about the axis of rotation 139, thereby generating an airflow in a direction 198, which is also referred to in the following for simplicity and clarity as "propulsive airflow 198". The propulsive airflow 198 is preferably generated at least for propelling the compound helicopter 100 in the forward flight state.

[0076] The propeller 130 and the main rotor 120 can preferably be driven completely independently from each other. In particular, different types of engines can be used for driving the propeller 130 and the main rotor 120, such as a gas- suction propulsion engine for the main rotor 120 and an electric motor for the propeller 130.

[0077] Illustratively, the propeller 130 is rotatably mounted on a shrouded duct 140 at the rear portion 114 of the fuselage 110 in the tail portion 102 of the compound helicopter 100. More specifically, the shrouded duct 140 is provided in the tail portion 102 and preferably forms an internal air duct 145 that at least partially accommodates the propeller 130. Accordingly, the propeller 130 forms a tail propeller and more particularly preferably a propulsive propeller. The propeller 130 can be mounted on the shrouded duct 140 by any suitable mechanism, such as a suitable fixed profile or strut. The shrouded duct 140 can be formed to generate a lateral thrust for main rotor counter torque at least in the forward flight state.

[0078] According to one aspect, the shrouded duct 140 includes a yaw and pitch stability enhancement unit, which is described in the following for Figures 8A to 23 yaw and pitch stability enhancement unit. The yaw and pitch stability enhancement unit is preferably provided for improving the yaw and pitch stability of the compound helicopter 100 in the forward flight state.

[0079] Illustratively, the rear portion 114 of the fuselage 110 extends between the front portion 112 of the fuselage 110 and the shrouded duct 140. The rear portion 114 preferably includes an asymmetric cross-sectional profile 190 in the direction of the roll axis R of the compound helicopter 100. According to one aspect, the rear portion 114 is configured to generate a lateral thrust for main rotor counter torque by main rotor downwash. By way of example, the asymmetric cross-sectional profile 190 is at least approximately C-shaped, as illustrated by a series of cross-sectional profiles 191, 193, 195, 197.

[0080] Additionally or alternatively, the rear portion 114 can comprise at least one airfoil-shaped aerodynamic device 150 extending from the front portion 112 to the tail portion 102, in particular to the shrouded duct 140. For example, only one airfoil-shaped aerodynamic device 150 is shown. The airfoil-shaped aerodynamic device 150 is illustratively arranged as an extension of the starboard side wall 104.

[0081] In an illustrative implementation, the airfoil-shaped aerodynamic device 150 is formed as or by a wing. However, the wing is not arranged transversely to the roll axis R, but at least substantially parallel to the roll axis R.

[0082] The airfoil-shaped aerodynamic device 150 can at least partially form the rear portion 114. More particularly, the airfoil-shaped aerodynamic device 150 can be configured to generate lateral thrust for main rotor counter torque by main rotor downwash.

[0083] The rear portion 114 can further comprise at least one wing-like aerodynamic device 160 extending between the front portion 112 and the shrouded duct 140. For example, only one wing-like aerodynamic device 160 is shown. Illustratively, the wing-like aerodynamic device 160 is at least substantially arranged as an extension of the port side wall 103.

[0084] Preferably, the wing-like aerodynamic device 160 is mounted on the shrouded duct 140 and the superstructure 105 of the compound helicopter 100. Illustratively, the wing-like aerodynamic device 160 and the airfoil-shaped aerodynamic device 150 are connected to opposite sides of the shrouded duct 140. The wing-like aerodynamic device 160 can further be configured to generate lateral thrust for main rotor counter torque by main rotor downwash of the compound helicopter 100.

[0085] Illustratively, the compound helicopter 100 further comprises a bare propeller drive shaft 170, in particular a cylindrical shaft as described below for Figure 5 or a conical shaft as described below for Figure 6 configured to generate a Magnus effect in main rotor downwash when rotating. The bare propeller drive shaft 170 as well as the shrouded duct 140 can be tilted and can be offset with respect to the roll axis R of the compound helicopter 100- as described above. Preferably, the bare propeller drive shaft 170 is configured to drive the propeller 130 in operation and illustratively extends uncoupled and load-free between the front portion 112 of the fuselage 110 and the propeller 130, i.e. without intermediate couplings and bearings.

[0086] The front portion 112 can further comprise one or more asymmetric sources, which are described below for Figure 4 The asymmetric sources can further be configured to generate lateral thrust for main rotor counter torque by main rotor downwash of the compound helicopter 100.

[0087] Figure 2 The composite helicopter 100 is shown Figure 1 The composite helicopter 100 has a fuselage 110, a main rotor 120, a propeller 130, a shrouded duct 140, and a bare propeller drive shaft 170. According to Figure 1 The fuselage 110 comprises a front portion 112 incorporated into a rear portion 114 at a recessed area 115, the rear portion 114 comprising an airfoil-shaped aerodynamic device 150 and a wing-like aerodynamic device 160, the propeller 130 is rotatably mounted on the shrouded duct 140 and driven by the bare propeller drive shaft 170, and the wing-like aerodynamic device 160 connects the upper deck 105 to the shrouded duct 140.

[0088] According to one aspect, the shrouded duct 140 forms a rear-swept structure 250 and illustratively comprises an upper side 203 and a lower side 204. This rear-swept structure 250 is preferably arranged to adapt the main rotor downwash at the shrouded duct 140 to the preferred characteristics of the composite helicopter 100 during the transition from hover to forward flight.

[0089] Illustratively, a bottom edge 210 of the rear portion 114 of the fuselage 110 is shown, which extends along the rear portion 114 to the lower side 204 of the shrouded duct 140. This bottom edge 210 is preferably inclined with respect to a horizontal reference plane 230 by a predetermined inclination angle 220. By way of example, the predetermined inclination angle 220 is a positive (upward) angle, which can be selected based on the required lateral thrust to be generated by the rear portion 114 of the fuselage 110 in operation.

[0090] However, it should be noted that the upward angle is merely by way of example represented and described, and is not therefore limiting to the present application. Furthermore, it should be noted that in addition to the selected illustrative upward angle, for example, a negative (downward) angle can also be selected for the predetermined inclination angle 220. In this case, an increase of up to 30% of the generated lateral thrust can be obtained, so that an increase of more than 40% of the corresponding generated counter moment can be achieved.

[0091] Furthermore, according to one aspect, a rear door 240 and / or additional equipment (e.g. a winch) can be provided in the recessed area 115. The rear door 240 can be, for example, a sliding door or a double cantilever door. By way of example, the rear door 240 can slide into the fuselage 110, i.e. slide towards the cabin 111. Thus, during forward flight with the door open, no additional drag is generated by the rear door 240.

[0092] Preferably, the rear door 240 is accessible from the rear side of the compound helicopter 100, i.e. from the rear portion 114. Thus, the cabin 111 of the compound helicopter can be loaded from the rear side. Advantageously, by positioning the rear door 240 in the recessed area 115, the overall aerodynamic performance of the compound helicopter 100 can be avoided to be impaired by the rear door 240.

[0093] Figure 3 The compound helicopter 100 is shown Figure 1 and Figure 2 having a fuselage 110, a main rotor 120, a propeller 130, a shrouded duct 140, and a bare propeller drive shaft 170. According to Figure 1 and Figure 2 the fuselage 110 comprises a front portion 112 incorporated into a rear portion 114 at a recessed area 115, the rear portion 114 comprising a wing- shaped aerodynamic device 150 and a wing-like aerodynamic device 160, the main rotor 120 comprises rotor blades 125, 126, 127, 128, 129 and a rotor hub 123 arranged in the front portion 112 of the fuselage 110, the propeller 130 is rotatably mounted on the shrouded duct 140 and driven by the bare propeller drive shaft 170, and the wing-like aerodynamic device 160 connects the upper deck 105 to the shrouded duct 140.

[0094] More particularly, Figure 3 the arrangement of the main rotor 120 and its rotor hub 123 in the front portion 112 of the fuselage 110 and the incorporation of the front portion 112 into the rear portion 114 of the fuselage 110 along the recessed area 115 by redirecting, i.e. deflecting, the port side wall 103 of the compound helicopter 100 in the recessed area 115 towards the starboard side wall 104 are illustrated. Furthermore, the connection of the wing-shaped aerodynamic device 150 and the wing-like aerodynamic device 160 to the substantially completely opposite sides 330, 340 of the shrouded duct 140, which correspond to the side of the starboard side wall 104 and the side of the port side wall 103, respectively, are illustrated. Preferably, at least the connection of the wing-shaped aerodynamic device 150 to the shrouded duct 140 is formed as a smooth transition 320, which preferably spans at least 25% of the total circumference of the shrouded duct 140.

[0095] For example, the width 310 of the wing-like aerodynamic device 160 increases over a predetermined length of the wing-like aerodynamic device 160 starting from the upper deck 105. More specifically, the width 310 illustratively increases starting at the upper deck 105 and in the direction of the shrouded duct 140.

[0096] The width 310 can increase such that a maximum width value is reached at an area between 60% of the length of the rotor blades 125, 126, 127, 128, 129 and their outer ends. Preferably, the width 310 increases at least over 75% of the length of the airfoil-shaped aerodynamic device 160. Illustratively, the airfoil-shaped aerodynamic device 160 reaches 75% of the length at the position 315.

[0097] Figure 4 The composite helicopter 100 is shown Figures 1 to 3 with a fuselage 110, a main rotor 120, a propeller 130, a shrouded duct 140, and a bare propeller drive shaft 170. According to Figures 1 to 3 , the fuselage 110 comprises a front portion 112 incorporated into a rear portion 114 at a recessed area 115, the rear portion 114 comprising an airfoil-shaped aerodynamic device 160, and the propeller 130 is rotatably mounted on the shrouded duct 140 and driven by the bare propeller drive shaft 170. However, the illustration of the airfoil-shaped aerodynamic device 160 is omitted for simplicity of the drawing.

[0098] More particularly, Figure 4 The connection of the airfoil-shaped aerodynamic device 150 to the shrouded duct 140 is illustrated. Furthermore, it is further illustrated that the front portion 112 is incorporated into the rear portion 114 of the fuselage 110 along the recessed area 115 by redirecting, i.e. deflecting, the port side wall 103 of the composite helicopter 100 in the recessed area 115 towards the starboard side wall 104.

[0099] For example, the at least one asymmetric source 410 is connected to the front portion 112, preferably close to the lower side 106 of the fuselage 110, such that the front portion 112 comprises, at least in cross-section, an asymmetric cross-sectional profile in the direction of the associated roll axis R of the composite helicopter 100. Figure 1 The at least one asymmetric source 410 is preferably configured to generate a lateral thrust for main rotor counter torque by main rotor downwash.

[0100] The at least one asymmetric source 410 can be formed as an integral part of the fuselage 110. Illustratively, the at least one asymmetric source 410 is implemented as an integrally formed flange of the fuselage 110. Alternatively, the at least one asymmetric source 410 can be pivotable and / or retractable, e.g. into the fuselage 110.

[0101] For example, the flange is formed as a plate-like protrusion 420 of the fuselage 110. The plate-like protrusion 420 is illustratively integrally formed with the fuselage 110. The plate-like protrusion 420 may, for example, form a step which can be used, e.g. to support an occupant entering the cabin 111 of the composite helicopter 100.

[0102] Figure 5 The composite helicopter 100 is shown Figures 1 to 4 The open-end propeller drive shaft 170, in one illustrative implementation, includes a large-diameter cylindrical shaft 510. The diameter of this large-diameter cylindrical shaft 510 is preferably in the range of 5 to 10 times the diameter of a conventional tail rotor drive shaft. Preferably, the large-diameter cylindrical shaft 510 is capable of generating the so-called Magnus effect to improve performance during operation. Figures 1 to 4 The main rotor of the compound helicopter 100 and the downwash flow of the main rotor 120 generate additional lateral thrust.

[0103] As mentioned above Figure 1 As described above, the coverless propeller drive shaft 170, and therefore the large-diameter cylindrical shaft 510, preferably extends uncoupled and unloaded between the front 112 of the fuselage 110 and the propeller 130. For illustrative purposes, the large-diameter cylindrical shaft 510 is therefore shown as having two suitable bearings 520, 530 at its axial ends, which are configured to rotatably support the large-diameter cylindrical shaft 510.

[0104] To achieve a decoupled and load-bearing extension of the large-diameter cylindrical shaft 510 between the front 112 of the fuselage 110 and the propeller 130, the large-diameter cylindrical shaft 510 must be sufficiently rigid for reliable and safe operation. This can be achieved by using carbon composite materials, especially high-modulus fibers, to form the large-diameter cylindrical shaft 510.

[0105] Figure 6 It shows Figures 1 to 4 The open-top propeller drive shaft 170, in another illustrative implementation, includes a large-diameter tapered shaft 610. The maximum diameter of this large-diameter tapered shaft 610 is preferably within the range of 5 to 10 times the diameter of a conventional tail rotor drive shaft. Preferably, the large-diameter tapered shaft 610 is also capable of generating the so-called Magnus effect to improve performance during operation. Figures 1 to 4 The main rotor of the compound helicopter 100 and the downwash flow of the main rotor 120 generate additional lateral thrust.

[0106] As mentioned above Figure 1 As described, the uncovered propeller drive shaft 170, and therefore the large-diameter tapered shaft 610, preferably extends uncoupled and unloaded between the front 112 of the fuselage 110 and the propeller 130. For illustrative purposes, the large-diameter tapered shaft 610 is therefore shown as having two suitable bearings 620, 630 at its axial ends, which are configured to rotatably support the large-diameter tapered shaft 610. Preferably, bearing 630 is located in... Figure 1 The propeller is supported at point 130 by a large-diameter conical shaft 610.

[0107] To achieve a decoupled and load-bearing extension of the large-diameter tapered shaft 610 between the front 112 of the fuselage 110 and the propeller 130, the large-diameter tapered shaft 610 must be sufficiently rigid for reliable and safe operation. This can be achieved by using carbon composite materials, especially high-modulus fibers, to form the large-diameter tapered shaft 610.

[0108] Figure 7 It shows Figures 1 to 4 The coverless propeller drive shaft 170 includes Figure 5 Large diameter cylindrical shaft 510 or Figure 6 A large-diameter tapered shaft 610. Figures 1 to 4 In one illustrative operation of the main rotor 120 of the compound helicopter 100, the capless propeller drive shaft 170 rotates in the main rotor downwash 730 in the rotation direction 720. Therefore, due to the Magnus effect, the capless propeller drive shaft 170 generates a lateral force 740. This lateral force 740, in turn, causes... Figures 1 to 4 Lateral thrust is applied to the rear part 114 of the fuselage 110 of the compound helicopter 100.

[0109] It should be noted that the Magnus effect is well known to those skilled in the art. Therefore, for the sake of brevity, the Magnus effect and its application in generating lateral thrust through the open-top propeller drive shaft 170 will not be described in more detail.

[0110] Figure 8A It shows in Figure 3 Observed from direction VIII Figures 1 to 4 A 140-degree culvert with a protective cover. Figure 1 The duct 140 with a protective shield in the internal air duct 145 illustratively includes an annular duct body 142 forming a trailing edge 141. Furthermore, as for... Figure 1 As described above, the duct 140 with a shield according to the invention includes a yaw and pitch stability enhancement unit 800. The yaw and pitch stability enhancement unit 800 is preferably configured at least partially to enhance yaw and pitch stability by... Figure 1 The propulsive airflow was deflected by 198 degrees. Figures 1 to 4 The compound helicopter 100 generates lateral thrust for the main rotor's anti-torque during forward flight, thereby providing... Figures 1 to 4 The composite helicopter 100 improves yaw and pitch stability.

[0111] According to one aspect, the yaw and pitch stability enhancement unit 800 includes a rudder 810. The rudder 810 is preferably rotatably mounted on a shielded duct 140 and is indicated to be in a neutral state, i.e., without deflection.

[0112] The rudder 810 preferably includes an elongated rudder body 815 and is preferably positioned perpendicularly to the annular duct body 142 of the duct 140 with a protective cover. Illustratively, the elongated rudder body 815 extends along an associated length axis 819 from an upper axial end 816 toward a lower axial end 818. For example, the center portion 814 of the elongated rudder body 815 is positioned at... Figures 1 to 4 The axis of rotation of the tail propeller 130 is located at 139.

[0113] The elongated rudder body 815 illustratively forms a leading edge 817 and a trailing edge 813. Preferably, the elongated rudder body 815, and more generally the rudder 810, is twisted about a length axis 819.

[0114] According to one aspect, the yaw and pitch stability enhancement unit 800 additionally or alternatively includes at least one strut 820. The at least one strut 820 includes an elongated strut body 825 and is preferably positioned horizontally relative to the annular duct body 142 of the ducted duct 140 with a shield. For example, the elongated strut body 825 is set at an angle of approximately 90° relative to the elongated rudder body 815.

[0115] Illustratively, the elongated strut body 825 extends along the associated length axis 829 from the left axial end 826 toward the right axial end 828. For example, the center portion 824 of the elongated strut body 825 relative to... Figures 1 to 4 The tail propeller 130 is positioned coaxially with the rotation axis 139.

[0116] The elongated strut body 825 illustratively forms a leading edge 827 and a trailing edge 823. Preferably, the elongated strut body 825, and more generally at least one strut 810, is twisted about a length axis 829.

[0117] According to one aspect, the yaw and pitch stability enhancement unit 800 additionally or alternatively includes at least one cap-shaped Fowler flap. Illustratively, two cap-shaped Fowler flaps 830, 840 are provided, for example, on completely opposite sides of the duct 140 with a shield. These cap-shaped Fowler flaps 830, 840 are referred to below... Figures 11 to 15B To describe in more detail.

[0118] Figure 8B It shows Figure 8A The duct 140 with a protective shield has an annular duct body 142 forming a trailing edge 141 and a leading edge 143. The annular duct body 142 forms an internal air duct 145. Figure 1 The propulsive airflow 198 is guided from the leading edge 143 to the trailing edge 141 through the internal air duct to propel the aircraft in the forward flight direction 199. Figures 1 to 4The composite helicopter 100. The ducted section 140 with a protective shield also includes... Figure 8A The yaw and pitch stability enhancement unit 800 illustratively includes a rudder 810 having a leading edge 817 and a trailing edge 813, at least one strut 820 having a leading edge 827 and a trailing edge 823, and cap-shaped Fowler flaps 830, 840. The rudder 810 is again shown to be in a neutral state, i.e., without deflection.

[0119] For example, the duct 140 with a protective shield and the through Figures 1 to 4 The propeller 130 is shown together with the circular propeller disk 135 formed by the rotation of the propeller 130 within the internal air duct 145 of the ducted duct 140. According to one aspect, the rudder 810 is positioned downstream of the circular propeller disk 135 in the forward flight direction 199, i.e., the circular propeller disk 135 is positioned closer to the leading edge 143 of the ducted duct 140 than the rudder 810. Similarly, at least one strut 820 is preferably positioned downstream of the circular propeller disk 135 in the forward flight direction 199, i.e., the circular propeller disk 135 is positioned closer to the leading edge 143 of the ducted duct 140 than the at least one strut 820.

[0120] Because the circular propeller disk 135 is positioned closer to the leading edge 143 of the shielded duct 140 than the rudder 810 and / or at least one strut 820, the rudder 810 and / or at least one strut 820 are positioned to propel in the forward flight direction 199. Figures 1 to 4 The propulsion airflow 198 of the compound helicopter 100. However, the propulsion airflow 198 not only has velocity in the rearward direction, but also around... Figure 8A The propeller axis 139 also exhibits superimposed rotation. This rotation is caused by... Figures 1 to 4 The rotation of the propeller 130 generates this effect. However, by positioning the rudder 810 and / or at least one strut 820 within the propulsive airflow 198 and making them both as directed... Figure 8A The aforementioned distortion allows the propulsion airflow 198 to be advantageously straightened, thus increasing the corresponding efficiency of the shielded duct 140 by at least a small percentage.

[0121] In any case, at least one support column 820 is preferably used as a fixed profile to support the duct 140 with a protective cover, and more specifically in the internal air duct 145. Figures 1 to 4 The propeller 130, and first transmits the thrust of the propeller 130 to the shielded duct 140 and then to... Figures 1 to 4The composite helicopter 100 of Fig. 1 comprises a fuselage 110, a tail boom 120, a main rotor 130, a tail rotor 140, a cockpit 150, a passenger cabin 160, a cargo hold 170, a landing gear 180, and a tail fin 190.

[0122] The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9. Figures 1 to 4 Figure 1 The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9. Figure 10A Figure 8A The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9. Figure 9A Figure 9B The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9.

[0123] Figure 9A The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9. Figure 8A Figure 8B The tail fin 190 is preferably provided at least for yaw control about the yaw axis Y of the composite helicopter 100 of Fig. 1. For this purpose, the tail fin 190 can be rotated about its length axis 819 as a whole, similar to a so-called oscillating tail fin, as described hereinafter for the tail fin 810 of Fig. 8, or it can be realized by a conventional discrete tail fin, as described hereinafter for the tail fin 910 of Fig. 9.

[0124] According to one aspect, the elongated tail fin body 815 comprises an airfoil-shaped profile 912 having a rectilinear center line 924. Illustratively, the airfoil-shaped profile 912, and thus the rectilinear center line 924, is rotated about the length axis 819 of the elongated tail fin body 815 between two axial end portions (816, 818) of the elongated tail fin body 815, such that the elongated tail fin body 815 is twisted about the length axis 819. Figure 8A Figure 8B More specifically, by a central airfoil profile 914 at a central portion 814 of the elongated tail fin body 815, an upper airfoil profile 916 at an upper axial end portion 816 of the elongated tail fin body 815, and a lower airfoil profile 917 at a lower axial end portion 818 of the elongated tail fin body 815.

[0125] More specifically, by a central airfoil profile 914 at a central portion 814 of the elongated tail fin body 815, an upper airfoil profile 916 at an upper axial end portion 816 of the elongated tail fin body 815, and a lower airfoil profile 917 at a lower axial end portion 818 of the elongated tail fin body 815. Figure 8A Figure 8B More specifically, by a central airfoil profile 914 at a central portion 814 of the elongated tail fin body 815, an upper airfoil profile 916 at an upper axial end portion 816 of the elongated tail fin body 815, and a lower airfoil profile 917 at a lower axial end portion 818 of the elongated tail fin body 815. Figure 8A Figure 8B More specifically, by a central airfoil profile 914 at a central portion 814 of the elongated tail fin body 815, an upper airfoil profile 916 at an upper axial end portion 816 of the elongated tail fin body 815, and a lower airfoil profile 917 at a lower axial end portion 818 of the elongated tail fin body 815. Figure 8A Figure 8B ​​​​​​​​The lower airfoil profile 918 at the lower axial end 818 forms the rudder 810. The center airfoil profile 914 is represented as having a straight centerline 924 in a non-rotating position, the upper airfoil profile 916 is represented as having a straight centerline 926 corresponding to the straight centerline 924 and rotating in a counterclockwise direction around the length axis 819, and the lower airfoil profile 918 is represented as having a straight centerline 928 corresponding to the straight centerline 924 and rotating in a clockwise direction around the length axis 819.

[0126] Figure 9A It can also be applied to Figure 8A and Figure 8B At least one strut 820 includes an elongated strut body 825 extending along a length axis 829, wherein the elongated strut body 825 forms a leading edge 827 and a trailing edge 823. In this case, the elongated strut body 825 includes an airfoil-shaped profile 912 having a straight centerline 924, wherein the airfoil-shaped profile 912, and therefore the straight centerline 924, surrounds the length axis 829 of the elongated strut body 825 at both axial ends of the elongated strut body 825. Figure 8A and Figure 8B Rotating between 826 and 828 in the middle, causing the elongated strut body 825 to twist about the length axis 829. Therefore, at least one strut 820 includes a structure located at... Figure 8A and Figure 8B The central airfoil profile at the center of the part 824 is 914, located at the center of the part 824. Figure 8A and Figure 8B The airfoil profile 916 at the left axial end 826 and located at Figure 8A and Figure 8B The airfoil profile 918 is located at the right axial end 828. Therefore, the center airfoil profile 914 is represented as having a straight centerline 924 in a non-rotating position, the airfoil profile 916 is represented as having a straight centerline 926 corresponding to the straight centerline 924 and rotating in the counterclockwise direction around the length axis 829, and the airfoil profile 918 is represented as having a straight centerline 928 corresponding to the straight centerline 924 and rotating in the clockwise direction around the length axis 829.

[0127] Figure 9B It shows that according to Figure 9A The airfoil profiles 914, 916, and 918 of the rudder 810 (or at least one strut 820). However, although airfoil profile 914 still includes Figure 9A The straight centerline 924, but the airfoil profiles 916 and 918 are now... Figure 9A Conversely, it includes arcuate centerlines 936 and 938 with varying curvature according to an alternative implementation.

[0128] In other words, the curvature of the centerlines 936 and 938 surrounds the length axis 819 (or 829) of the slender rudder body 815 (or slender strut body 825) from the center ( Figure 8A and Figure 8B The two axial ends of the 814 or 824 in the middle are oriented toward the slender rudder body 815 (or the slender strut body 825). Figure 8A and Figure 8B The slender rudder body 815 (or slender strut body 825) is twisted by variations in 816, 818, 826, or 828. For example, centerline 936 is illustratively bent in a counterclockwise direction, and centerline 938 is illustratively bent in a clockwise direction.

[0129] Figure 10A It shows that according to Figure 9A The airfoil profiles 914, 916, and 918 of the rudder 810 (or at least one strut 820). However, with Figure 9A Conversely, all airfoil profiles 914, 916, and 918 now include the curved centerline 934.

[0130] Figure 10B The airfoil profile 914 of the rudder 810 (or at least one strut 820) is shown to have a shape according to Figure 10A The arc-shaped centerline is 934. However, with Figure 10A Instead, the twisting of the slender rudder body 815 (or slender strut body 825) is now achieved by providing one or more rudder flaps to the slender rudder body 815 (or slender strut body 825). For example, two rudder flaps 1050, 1060 are shown, which deflect in opposite directions, for example.

[0131] If the slender rudder body 815 is provided with one or more rudder flaps 1050, 1060, then such rudder 810 can be fixedly mounted. Figure 8A and Figure 8B On the duct 140 with a protective shield. In other words, as long as the rudder 810 as a whole or the rudder flaps 1050 and 1060 rotate together or separately.

[0132] Figure 11 It shows Figure 8A and Figure 8B The duct 140 with a protective shield has an annular duct body 142 forming a trailing edge 141 and a leading edge 143. The annular duct body 142 forms an internal air duct 145. Figure 1 The propulsive airflow 198 is guided from the leading edge 143 toward the trailing edge 141 through the internal air duct. The duct 140 with a shield also includes Figure 8A and Figure 8B yaw and pitch stability augmentation unit 800. However, in contrast to Figure 8A and Figure 8B the yaw and pitch stability augmentation unit 800 now only comprises the cap- Fowler flaps 830, 840, such that in the selected implementation also the rudder 810 and the at least one strut 820 according to Figure 8A and Figure 8B can be omitted. Furthermore, it is noted that also the cap-Fowler flap 840 can be omitted.

[0133] Illustratively, the cap-Fowler flaps 830, 840 are provided on or adjacent to the trailing edge 141 of the shrouded duct 140. Preferably, the cap-Fowler flaps 830, 840 at least partially form the trailing edge 141 of the shrouded duct 140 in the associated neutral position.

[0134] According to one aspect, the cap-Fowler flaps 830, 840 are at least partially deployable from and / or at least partially retractable into the annular duct body 142 of the shrouded duct 140. By way of example, the cap-Fowler flap 830 is shown in the associated neutral position, but also in a fully deployed position. In this fully deployed position, the cap-Fowler flap is denoted by reference numeral 832. Similarly, the cap-Fowler flap 840 is shown in the associated neutral position, but for example also in a fully retracted position. In this fully retracted position, the cap-Fowler flap is denoted by reference numeral 842.

[0135] Figure 12A a shrouded duct 140 according to Figure 11 is shown having an annular duct body 142 comprising a trailing edge 141 and a leading edge 143. The shrouded duct 140 further comprises a cap-Fowler flap 840, which is shown in the associated neutral position in which the cap-Fowler flap 840 illustratively forms the trailing edge 141 of the shrouded duct 140, as well as in a fully retracted position in which the cap-Fowler flap is further retracted into the shrouded duct 140 and is denoted by reference numeral 842.

[0136] More specifically, according to one aspect, the annular duct body 142 comprises a hollow interior 144. As shown, the hollow interior 144 is preferably formed such that the cap-Fowler flaps 840, 842 are at least partially accommodated in the hollow interior 144 in the associated neutral position (840) as well as in the fully retracted position (842).

[0137] Figure 12B a shrouded duct 140 according to Figure 11The shrouded duct 140 has a ring-shaped duct body 142 comprising a trailing edge 141 and a leading edge 143. The shrouded duct 140 further comprises a cap-type Fowler flap 830, which is shown in an associated neutral position in which the cap-type Fowler flap 830 illustratively forms the trailing edge 141 of the shrouded duct 140, as well as a fully deployed position in which the cap-type Fowler flap is fully extended and unfolded from the shrouded duct 140 and is denoted by reference numeral 832.

[0138] More specifically, as described above for Figure 12A the ring-shaped duct body 142 preferably comprises a hollow interior 144. As shown, the hollow interior 144 is preferably formed such that the cap-type Fowler flap 830, 832 can be at least partially accommodated in the hollow interior 144 in the associated neutral position (830) and extended and unfolded therefrom into the fully deployed position (832).

[0139] Figure 13A A shrouded duct 140 is shown having a trailing edge 141 and a leading edge 143, in accordance with Figure 12B wherein the shrouded duct 140 has a ring-shaped duct body 142 forming a hollow interior 144. Figure 13A Also shown is a cap-type Fowler flap 830 in an associated neutral position, wherein the cap-type Fowler flap 830 is at least partially accommodated in the hollow interior 144 and forms the trailing edge 141 of the shrouded duct 140.

[0140] Figure 13B A shrouded duct 140 is shown having a trailing edge 141 and a leading edge 143, in accordance with Figure 12B wherein the shrouded duct 140 has a ring-shaped duct body 142 forming a hollow interior 144. Figure 13B Also shown is a cap-type Fowler flap 832 in a fully deployed position, wherein the cap-type Fowler flap 832 is spaced apart from the ring-shaped duct body 142 by a predetermined gap 1310.

[0141] However, the predetermined gap 1310 can create aerodynamic disadvantages at the trailing edge 141. These aerodynamic disadvantages can be prevented by adjusting the cap-type Fowler flap 830, as will be described in detail below for Figures 14A to 15B the shrouded duct 140.

[0142] Figure 14A A shrouded duct 140 is shown having a trailing edge 141 and a leading edge 143, in accordance with Figure 13A wherein the shrouded duct 140 has a ring-shaped duct body 142 forming a hollow interior 144, wherein a cap-type Fowler flap 830 is at least partially accommodated in an associated neutral position such that it forms the trailing edge 141 of the shrouded duct 140. However, in contrast to Figure 13A In contrast, the cap Fowler flap 830 is now formed as a multipart component, which illustratively comprises two separate flap components 1410, 1420, which are preferably spaced apart from each other. Both separate flap components 1410, 1420 are preferably simultaneously deployable from the annular duct body 142.

[0143] Figure 14B A shrouded duct 140 with a trailing edge 141 and a leading edge 143 is shown according to Figure 14A , wherein the shrouded duct 140 has an annular duct body 142 forming a hollow interior 144. However, in contrast to Figure 14A , the cap Fowler flap 832 with the two separate flap components 1410, 1420 is now shown in a fully deployed position, wherein the flap component 1420 preferably forms the trailing edge 141 of the shrouded duct 140, while the flap component 1410 is shown spaced apart from the annular duct body 142.

[0144] Figure 15A A shrouded duct 140 with a trailing edge 141 and a leading edge 143 is shown according to Figure 13A , wherein the shrouded duct 140 has an annular duct body 142 forming a hollow interior 144, wherein the cap Fowler flap 830 is at least partially accommodated in an associated neutral position to form the trailing edge 141 of the shrouded duct 140. However, in contrast to Figure 13A , the cap Fowler flap 830 now forms with Figure 14A the flap component 1410 and an extension 1520 abutting and thus lengthening the flap component 1410 in the direction of the leading edge 143 of the shrouded duct 140.

[0145] Figure 15B A shrouded duct 140 with a trailing edge 141 and a leading edge 143 is shown according to Figure 15A , wherein the shrouded duct 140 has an annular duct body 142 forming a hollow interior 144. However, in contrast to Figure 15A , the cap Fowler flap 832 with the flap component 1410 and the extension 1520 is now shown in a fully deployed position.

[0146] Figure 16 A shrouded duct 140 with a trailing edge 141 and a leading edge 143 is shown according to Figure 11 , wherein the shrouded duct 140 has an annular duct body 142 forming an internal air duct 145. The shrouded duct 140 comprises a yaw and pitch stability augmentation unit 800.

[0147] However, in contrast to Figure 11Conversely, the yaw and pitch stability enhancement unit 800 is now described as comprising multiple airfoil-shaped aerodynamic devices 1610, 1620, 1630, 1640, particularly high-lift airfoils, rather than... Figure 11 The cap-shaped Fowler flaps 830 and 840. The airfoil-shaped aerodynamic devices 1610, 1620, 1630, and 1640 are preferably configured to be substantially similar to... Figure 1 The associated roll axis R of the compound helicopter 100 is parallel and forms a transition from the rear 114 of the compound helicopter 100 to the leading edge 143 of the covered duct 140. Illustratively, airfoil-shaped aerodynamic devices 1610, 1620, 1630, and 1640 are connected to a portion 1600 of the covered duct 140, the axial length of which is shorter than the rest of the covered duct 140.

[0148] More specifically, the duct 140 with a protective shield is rearward in a portion 1600 located in the lower region of the duct 140 with a protective shield. In this lower region, Figures 1 to 4 The downwash from the main rotor 120 of the compound helicopter 100 impacts the ducted duct 140, which is shielded, substantially perpendicularly, generating an aerodynamic disruptive flow that in turn produces strong aerodynamic drag in the direction of the downwash. This drag occurs within the internal air duct 140. Figures 1 to 4 The propeller 130 is enlarged when it simultaneously draws in airflow. Therefore, in the lower region, more specifically in section 1600, it is advantageous to reduce the depth, i.e., the axial length, of the duct 140 with a shield, as described above. Thus, the airfoil-shaped aerodynamic devices 1610, 1620, 1630, and 1640 can laterally deflect the aerodynamically disruptive flow and thereby use the latter to target Figures 1 to 4 The torque generated by the main rotor 120 of the compound helicopter 100 produces additional counter-torque. This in Figures 1 to 4 The compound helicopter 100 is particularly advantageous in the corresponding transition phase between pure hovering and forward flight.

[0149] Figure 17 It shows that according to Figures 8A to 16 Any of the following is a duct 140 with a protective shield, having an annular duct body 142 and a leading edge 143. According to one aspect, the leading edge 143 is now alternatively or additionally provided with a plurality of spaced-apart nodes 1750. The plurality of spaced-apart nodes 1750 may be provided in one or more selected portions of the periphery of the annular duct body 142 or along the entire periphery.

[0150] Figure 18A It shows that according to Figure 8A and Figure 8Ba shrouded duct 140 with a trailing edge 141 and a leading edge 143, wherein the shrouded duct 140 has an annular duct body 142 forming an inner air duct 145. The shrouded duct 140 further comprises Figure 8A and Figure 8B a yaw and pitch stability augmentation unit 800. However, in contrast to Figure 8A and Figure 8B the yaw and pitch stability augmentation unit 800 now only comprises a rudder 810 with an elongated rudder body 815 and at least one strut 820 with an elongated strut body 825, thereby in selected implementations representing that the flap 830, 840 according to Figure 8A and Figure 8B can be omitted.

[0151] According to one aspect, the leading edge 817 of the elongated rudder body 815 of the rudder 810 is now alternatively or additionally provided with a plurality of spaced-apart nodules 1850. Additionally or alternatively, the leading edge 827 of the elongated strut body 825 can be provided with a plurality of spaced-apart nodules 1850. In both cases, the leading edges 817, 827 can be provided with spaced-apart nodules 1850 in one or more portions or over their entire length.

[0152] Figure 18B The elongated rudder body 815 of the rudder 810 according to Figure 18A is shown with spaced-apart nodules 1850 on the leading edge 817, which are enlarged for the sake of clarity. Figure 18B The same can be applied analogously to the at least one strut 820 according to Figure 18A and therefore the elongated strut body 825 of the at least one strut 820 according to Figure 18A is also shown with spaced-apart nodules 1850 on the leading edge 827.

[0153] As mentioned above with regard to Figures 17 to 18B the leading edge 143 of the shrouded duct 140 can be provided with a plurality of spaced-apart nodules 1750 and / or the leading edge 817 of the elongated rudder body 815 of the rudder 810 can be provided with a plurality of spaced-apart nodules 1850 and / or the leading edge 827 of the elongated strut body 825 of the at least one strut 820 can be provided with a plurality of spaced-apart nodules 1850. Accordingly, the respective airflow splitting at the leading edges 143, 817 and / or 827 can be translated into a higher angle of attack. Thus, such airflow splitting, which would result in high drag and increase the disturbance of the airflow within the shrouded duct 140, can advantageously be avoided or at least substantially reduced. Thus, the basic efficiency of the shrouded duct 140, the rudder 810 and / or the at least one strut 820 is not reduced as much at least for high deflection angles of these components, as the airflow is not split.

[0154] Figure 19A It shows that according to Figure 8A and Figure 8B A duct 140 with a trailing edge 141 and a protective shield, wherein the duct 140 with the protective shield has an annular duct body 142 forming an internal air duct 145. The duct 140 with the protective shield also includes Figure 8A and Figure 8B The yaw and pitch stability enhancement unit 800. However, with Figure 8A and Figure 8B Conversely, the yaw and pitch stability enhancement unit 800 now includes only a rudder 810 with an elongated rudder body 815 and at least one strut 820 with an elongated strut body 825, thus representing an omissionable feature in the chosen implementation. Figure 8A and Figure 8B The cap-shaped Fowler-style flaps 830 and 840.

[0155] According to one aspect, the rudder 810, forming the leading edge 813 and the trailing edge 817, and more specifically the elongated rudder body 815, now takes on a wave shape 1910. Illustratively, the wave shape 1910 corresponds at least substantially to an S-shape, which forms two inflection points 1912 and 1914 between the two axial ends 816 and 818 of the elongated rudder body 815. However, other wave shapes are also conceivable, such as a simple C-shape with a single inflection point, a double S-shape with four inflection points, and so on.

[0156] Preferably, the waveform shape 1910 is formed as an out-of-plane waveform. More specifically, the corresponding rudder body plane 1920 is illustratively formed by a virtual connection between the leading edge 813 at the axial ends 816, 818 and the trailing edge 817 at the axial ends 816, 818. Thus, the axial ends 816, 818 and the central portion 814 of the elongated rudder body 815 are located in the rudder body plane 1920, while this elongated rudder body 815 is substantially outside the rudder body plane 1920 and thus exhibits an out-of-plane waveform.

[0157] Figure 19B It shows that according to Figure 19A The duct 140 with a shield has a yaw and pitch stability enhancement unit 800, which includes a rudder 810 with an elongated rudder body 815 and at least one strut 820. Figure 19B The waveform shape 1910 of the slender rudder body 815 relative to... is also shown. Figure 19A The rudder body plane 1920 is in the form of an out-of-plane wave. By providing an elongated rudder body 815 with a wave shape 1910, and... Figure 8A and Figure 8BCompared to the straight rudder shown, the propeller blades ( ) are located upstream of the rudder 810. Figure 1 The eddies generated in (132) will not all impact the rudder simultaneously. Therefore, significant noise sources can be eliminated and noise generation can be significantly reduced accordingly.

[0158] However, any deflection of the rudder 810 will cause the slender rudder body 815 to remain at least near the propeller blades. Figure 1 The portion of 132) is moved. To avoid this, alternative out-of-plane waveforms or in-plane waveforms combined with them, as described below, may be advantageous.

[0159] Figure 20A and Figure 20B It shows that according to Figure 8A and Figure 8B A duct 140 with a trailing edge 141 and a protective shield, wherein the duct 140 with the protective shield has an annular duct body 142 forming an internal air duct 145. The duct 140 with the protective shield also includes Figure 8A and Figure 8B The yaw and pitch stability enhancement unit 800. However, with Figure 8A and Figure 8B Conversely, the yaw and pitch stability enhancement unit 800 now includes only a rudder 810 with an elongated rudder body 815 and at least one strut 820 with an elongated strut body 825, thus representing an omissionable feature in the chosen implementation. Figure 8A and Figure 8B The cap-shaped Fowler-style flaps 830 and 840.

[0160] Similar to Figure 19A and Figure 19B The rudder 810, forming the leading edge 813 and trailing edge 817, and more specifically the elongated rudder body 815, is characterized by a wave-like shape now indicated by reference numeral 2010. Illustratively, the wave-like shape 2010 corresponds at least substantially to a double C-shape, which forms three inflection points 2012, 2014, and 2016 between the two axial ends 816 and 818 of the elongated rudder body 815. However, other wave-like shapes are also conceivable, such as a simple C-shape with a single inflection point, a quadruple C-shape with five inflection points, and so on.

[0161] Preferably, the waveform shape 2010 is formed as an in-plane waveform. More specifically, the corresponding rudder body plane 2020 is illustratively formed by a virtual connection between the leading edge 813 at the axial ends 816, 818 and the trailing edge 817 at the axial ends 816, 818. Thus, the rudder body plane 2020 illustratively corresponds to Figure 20Bthe layer in the figure and the elongated rudder body 815 is fully located in this layer, i.e. in the rudder body plane 2020, thus appearing as an in-plane wave shape.

[0162] Figure 21A and Figure 21B shows a shrouded duct 140 with a trailing edge 141 according to Figure 8A and Figure 8B where the shrouded duct 140 has an annular duct body 142 forming an inner air duct 145. The shrouded duct 140 further comprises Figure 8A and Figure 8B a yaw and pitch stability augmentation unit 800. However, contrary to Figure 8A and Figure 8B the yaw and pitch stability augmentation unit 800 now only comprises a rudder 810 with an elongated rudder body 815 and at least one strut 820 with an elongated strut body 825, thus indicating in selected implementations that the cap Fowler flap 830, 840 according to Figure 8A and Figure 8B may be omitted.

[0163] According to one aspect, the rudder 810, more specifically the elongated rudder body 815, now appears as a Figure 19A and Figure 19B combination of the wave shape 1910 according to Figure 20A and Figure 20B the wave shape 2010 according to

[0164] Figure 22 and Figure 23 shows a shrouded duct 140 with a leading edge 143 and a trailing edge 141 according to Figure 8A and Figure 8B where the shrouded duct 140 has an annular duct body 142 forming an inner air duct 145. The shrouded duct 140 further comprises Figure 8A and Figure 8B a yaw and pitch stability augmentation unit 800. However, contrary to Figure 8A and Figure 8B the yaw and pitch stability augmentation unit 800 now only comprises a rudder 810 with an elongated rudder body 815 and at least one strut 820 with an elongated strut body 825.

[0165] According to one aspect, the trailing edge 141 of the shrouded duct 140 is now formed as a wave edge 2210. The wave edge 2210 is preferably at least arranged for reducing noise generation at the shrouded duct 140.

[0166] For example, the wave-shaped edge 2210 is formed in the Figure 22 by a plurality of V-shaped sections 2210, i.e. by a toothing protrusion formed in the axial direction of the shrouded duct 140. In Figure 23 , the wave-shaped edge 2210 is illustratively formed by a wavy border having protrusions formed in the radial direction of the shrouded duct 140.

[0167] Here, it is noted that the shrouded duct 140 is described above as being provided with a yaw and pitch stability enhancement unit 800, which in turn is described as having different components according to different embodiments. In other words, the yaw and pitch stability enhancement unit 800 is described as comprising one or more rudders 810, at least one strut 820, a hat Fowler flap 830, 840, and an airfoil-shaped aerodynamic device 1610, 1620, 1630, 1640. Furthermore, the rudder 810 and / or the at least one strut 820 can be provided with spaced-apart nodules 1850. Moreover, the rudder 810 can have a wave-shaped shape 1910, 2010. In addition, the leading edge 143 of the shrouded duct 140 can be provided with spaced-apart nodules 1750 and / or its trailing edge 141 can be provided with a wave-shaped edge 2210. However, any suitable combination of these features other than those described above can also be conceivable and can be determined according to the underlying construction of the compound helicopter 100 according to Figures 1 to 4 , which is within the common general knowledge of the skilled person.

[0168] Furthermore, it is noted that modifications of the above-described embodiments are also within the common general knowledge of the skilled person and are therefore also considered to be part of the present application. For example, the above-described airfoil-shaped aerodynamic device 150 can be implemented as one, two or more separate airfoil-shaped aerodynamic devices. Similarly, instead of being provided with a single wing-type aerodynamic device 160, more than two wing-type aerodynamic devices can also be provided.

[0169] In addition, the above-described shrouded duct 140 can be at least partially reduced in length, i.e. have a reduced or concave portion 1600, or have another cut-out, e.g. which can be provided in the bottom of the shrouded duct 140 between the airfoil-shaped aerodynamic device 150 and the wing-type aerodynamic device 160. Additionally or alternatively, the respective leading edge 143 and trailing edge 141 of the above-described shrouded duct 140 can be moved forward or backward in the direction of the roll axis R of the Figure 1 compound helicopter 100 according to

[0170] List of reference signs

[0171] 100 rotary wing aircraft

[0172] 101 aircraft head

[0173] 102 aircraft tail

[0174] 103 port side wall

[0175] 104 starboard side wall

[0176] 105 aircraft upper deck

[0177] 106 fuselage lower side

[0178] 110 fuselage

[0179] 111 nacelle

[0180] 112 fuselage front

[0181] 114 fuselage rear

[0182] 115 recessed area

[0183] 116 fuselage upper limit

[0184] 118 upper deck fairing

[0185] 120 main rotor

[0186] 122 rotor plane

[0187] 123 rotor hub

[0188] 124 rotor mast

[0189] 125, 126, 127, 128, 129 rotor blades

[0190] 130 tail propeller

[0191] 132 propeller blades

[0192] 135 tail propeller disc

[0193] 139 tail propeller rotation axis

[0194] 140 shrouded duct

[0195] 141 trailing edge of shrouded duct

[0196] 142 annular duct body

[0197] 143 leading edge of shrouded duct

[0198] 144 hollow interior

[0199] 145 air duct

[0200] 150 airfoil-shaped aerodynamic device

[0201] 160 wing aerodynamic device

[0202] 170 unshrouded propeller drive shaft

[0203] 190 rear asymmetric cross-sectional profile

[0204] 191, 193, 195, 197 asymmetric cross-sectional profile

[0205] 199 forward flight direction

[0206] 203, 204 opposite sides of shrouded duct

[0207] 210 bottom edge

[0208] 220 bottom edge tilt angle

[0209] 230 horizontal reference plane

[0210] 240 aircraft rear door

[0211] 250 rearward sweep configuration

[0212] 310 wing aerodynamic device width

[0213] 315 75% length limit

[0214] 320 smooth transition

[0215] 330, 340 opposite sides of shrouded duct

[0216] 350 viewing direction

[0217] 410 asymmetric source

[0218] 420 plate-like protrusion

[0219] 510 large diameter cylindrical shaft

[0220] 520, 530 bearing

[0221] 610 large diameter conical shaft

[0222] 620, 630 bearing

[0223] 720 propeller drive shaft rotation direction

[0224] 730 main rotor downwash

[0225] 740 lateral force

[0226] 800 yaw and pitch stability augmentation unit

[0227] 810 rudder

[0228] 813 rudder body trailing edge

[0229] 814 rudder center section

[0230] 815 elongate rudder body

[0231] 816 rudder upper axial end

[0232] 817 rudder body leading edge

[0233] 818 rudder lower axial end

[0234] 819 rudder body length axis

[0235] 820 horizontal strut

[0236] 823 strut body trailing edge

[0237] 824 strut center section

[0238] 825 elongate strut body

[0239] 826 strut left side section

[0240] 827 strut body leading edge

[0241] 828 strut right side section

[0242] 829 strut body length axis

[0243] 830, 840 Fowler flap

[0244] 832 fully extended Fowler flap

[0245] 842 fully retracted Fowler flap

[0246] 912 airfoil shaped profile

[0247] 914 center airfoil profile

[0248] 916 upper airfoil profile

[0249] 918 lower airfoil profile

[0250] 924, 926, 928 airfoil profile straight centerline

[0251] 934, 936, 938 airfoil profile curved centerline

[0252] 1050, 1060 rudder flap

[0253] 1310 gap

[0254] 1410, 1420 individual flap components

[0255] 1520 flap extension

[0256] 1600 shortened portion of shrouded duct

[0257] 1610, 1620, 1630, 1640 airfoil-shaped aerodynamic device

[0258] 1750 shrouded duct leading edge bump

[0259] 1850 rudder or strut leading edge bump

[0260] 1910 out-of-plane wave shape

[0261] 1912, 1914 inflection points

[0262] 1920 rudder body plane

[0263] 2010 in-plane wave shape

[0264] 2012, 2014, 2016 inflection points

[0265] 2020 rudder body plane

[0266] 2210 wavy edge

[0267] H height axis

[0268] P aircraft pitch axis

[0269] R aircraft roll axis

[0270] Y aircraft yaw axis

Claims

1. A rotary-wing aircraft extending between a nose and a tail along an associated roll axis and comprising a fuselage having a front and a rear portion, said rotary-wing aircraft comprising: The main rotor is configured to provide lift in the hovering state of the rotary-wing aircraft. A propeller, which is at least configured to propel the rotary-wing aircraft in a forward flight direction in a forward flight state, the propeller comprising a predetermined number of propeller blades that form a circular propeller disk as the propeller rotates about an associated axis of rotation; A duct with a protective shield is disposed in the tail section and forms an internal air duct that at least partially accommodates the propeller. The rear portion extends between the front portion and the shrouded duct and includes an asymmetrical cross-sectional profile in the direction of the associated roll axis. The rear portion is configured to generate lateral thrust for the main rotor's counter-torque through the main rotor downwash. The duct with the shield includes yaw and pitch stability enhancement units to improve the yaw and pitch stability of the rotary-wing aircraft in the forward flight state.

2. The rotary-wing aircraft according to claim 1, wherein, The yaw and pitch stability enhancement unit includes a rudder positioned downstream of the circular propeller disk in the forward flight direction, the rudder including an elongated rudder body twisted about the length axis (819) of the elongated rudder body.

3. The rotary-wing aircraft according to claim 2, wherein, The slender rudder body includes a leading edge with multiple spaced-apart nodules.

4. The rotary-wing aircraft according to claim 2, wherein, The elongated rudder body includes an airfoil-shaped profile having a straight centerline that rotates about the length axis of the elongated rudder body between the two axial ends of the elongated rudder body, or an arcuate centerline that includes varying curvature between the two axial ends of the elongated rudder body.

5. The rotary-wing aircraft according to claim 2, wherein, The rudder is rotatably mounted on the duct with a protective cover or is provided with one or more rotating flaps.

6. The rotary-wing aircraft according to claim 1, wherein, The yaw and pitch stability enhancement unit includes at least one strut disposed downstream of the circular propeller disk in the forward flight direction, the at least one strut including an elongated strut body that is twisted about the length axis of the elongated strut body.

7. The rotary-wing aircraft according to claim 6, wherein, The slender pillar body includes a leading edge with multiple spaced-apart nodules.

8. The rotary-wing aircraft according to claim 6, wherein, The elongated strut body includes an airfoil-shaped profile having a straight centerline that rotates about the length axis of the elongated strut body between two axial ends of the elongated strut body, or having an arcuate centerline that includes varying curvature between the two axial ends of the elongated strut body.

9. The rotary-wing aircraft according to claim 1, wherein, The yaw and pitch stability enhancement unit includes at least one hat-shaped Fowler flap.

10. The rotary-wing aircraft according to claim 9, wherein, The duct with a protective cover includes an annular duct body, and wherein at least one cap-shaped Fowler flap is at least partially retractable into the annular duct body.

11. The rotary-wing aircraft according to claim 9, wherein, At least one cap-shaped Fowler flap is disposed on the trailing edge of the duct with a protective cover.

12. The rotary-wing aircraft according to claim 11, wherein, The at least one cap-shaped Fowler flap, in the neutral position, at least partially forms the trailing edge of the shrouded duct.

13. The rotary-wing aircraft according to claim 1, wherein, The yaw and pitch stability enhancement unit includes multiple airfoil-shaped aerodynamic devices, particularly high-lift airfoils, which are arranged at least substantially parallel to the associated roll axis and form a transition from the rear to the leading edge of the shrouded duct.

14. The rotary-wing aircraft according to claim 1, wherein, The duct with a protective cover includes a leading edge with multiple spaced-apart nodules.

15. The rotary-wing aircraft according to claim 1, wherein, The rear portion includes at least one airfoil-shaped aerodynamic device extending from the front portion to the tail portion, and wherein the at least one airfoil-shaped aerodynamic device is configured to generate lateral thrust for the main rotor's counter-torque through the main rotor downwash.

16. The rotary-wing aircraft according to claim 1, wherein, The duct with the protective cover is annular.

17. The rotary-wing aircraft according to claim 1, wherein, The yaw and pitch stability enhancement unit includes a rudder rotatably mounted to the duct with a shield.

18. A rotary-wing aircraft extending between a nose and a tail along an associated roll axis and comprising a fuselage having a front and a rear portion, the rotary-wing aircraft comprising: The main rotor is configured to provide lift during the hovering state of the rotary-wing aircraft. A propeller configured to propel the rotary-wing aircraft in a forward flight direction during forward flight, the propeller comprising a plurality of propeller blades that form a circular propeller disk as the propeller rotates about an associated axis of rotation; A duct with a protective shield is disposed in the tail section and forms an annular internal air duct that at least partially accommodates the propeller. The rear portion extends between the front portion and the shrouded duct and includes an asymmetrical cross-sectional profile along the associated roll axis in the direction of the associated roll axis. The rear portion is configured to generate lateral thrust for the main rotor's counter-torque through the main rotor downwash flow. The duct with a shield includes a yaw and pitch stability enhancement unit mounted on the duct with a shield to improve the yaw and pitch stability of the rotary-wing aircraft in the forward flight state.

19. A rotary-wing aircraft extending between a head and a tail along a roll axis and comprising a fuselage having a front and a rear portion, the rotary-wing aircraft comprising: The main rotor provides lift during the hovering state of the rotary-wing aircraft; A propeller that propels the rotary-wing aircraft in the forward flight direction during forward flight, the propeller comprising multiple propeller blades that form a circular propeller disk as the propeller rotates about a rotation axis; A closed, shielded duct is disposed in the tail section and forms a closed internal air duct that at least partially accommodates the propeller. The rear portion extends between the front portion and the shrouded duct and includes an asymmetrical cross-sectional profile in the direction of the roll axis. The rear portion generates lateral thrust for the main rotor's counter-torque through the main rotor downwash. The duct with the shield includes yaw and pitch stability enhancement units to improve the yaw and pitch stability of the rotary-wing aircraft in the forward flight state.

20. The rotary-wing aircraft according to claim 19, wherein, The duct with a shield is annular, the propeller includes multiple propeller blades within the annular duct with a shield, and the yaw and pitch stability enhancement unit includes a rudder rotatably mounted to the duct with a shield.

Images