Rotorcraft

Abstract

A rotorcraft (10) has a body (11) and a main rotor (12) provided on an upper part of the body. The main rotor rotates in the counterclockwise direction or the clockwise direction when viewed from above the body. The rotorcraft has an auxiliary blade (14) provided to the body. The auxiliary blade is provided at a port front part of the body if the rotation direction of the main rotor is the counterclockwise direction. The auxiliary blade is provided at a starboard front part of the body if the rotation direction of the main rotor is the clockwise direction.

Description

rotorcraft

[0001] The present disclosure relates to rotorcraft.

[0002] Conventionally, there are rotary-wing aircraft with a main rotor mounted on top of the fuselage. Rotary-wing aircraft use lift generated by the rotation of the main rotor to stop in the air or fly forward. For example, the rotary-wing aircraft described in Patent Documents 1 to 3 have wings on the port and starboard sides of the fuselage.

[0003] U.S. Patent No. 7,438,259 U.S. Patent No. 8,763,949 U.S. Patent No. 9,527,577

[0004] The main rotor is the source of vibration in a rotary-wing aircraft. Vibrations from the main rotor are transmitted to the aircraft body via, for example, the transmission, which transmits the engine's driving force to the main rotor. Rotorcraft are required to suppress vibrations from the aircraft body.

[0005] A rotary-wing aircraft according to one aspect of the present disclosure includes an airframe and a main rotor mounted on an upper portion of the airframe. The main rotor is configured to rotate counterclockwise or clockwise when viewed from above the airframe. The rotary-wing aircraft also includes an aileron mounted on the airframe. The aileron is mounted on the port front of the airframe when the main rotor rotates counterclockwise, and is mounted on the starboard front of the airframe when the main rotor rotates clockwise.

[0006] Fig. 1 is a perspective view of a rotary-wing aircraft according to one embodiment. Fig. 2 is a graph showing the relationship between the angle of attack and lift coefficient of the rotary-wing aircraft of Fig. 1. Fig. 3 is a perspective view showing the vicinity of an aileron of a rotary-wing aircraft according to another embodiment. Fig. 4 is a perspective view showing the vicinity of an aileron of a rotary-wing aircraft according to another embodiment.

[0007] 1, the rotary wing aircraft 10 is, for example, a single rotor helicopter, and has an airframe 11, a main rotor 12, and a tail rotor 13.

[0008] The aircraft 11 has a horizontal stabilizer 11A and a vertical stabilizer 11B. The horizontal stabilizer 11A and the vertical stabilizer 11B are located aft of the aircraft 11, i.e., at the very rear of the aircraft 11. The horizontal stabilizer 11A provides the aircraft 11 with stability around the pitching axis Oy, i.e., in the vertical direction. The pitching axis Oy is an axis that passes through the aircraft 11's center of gravity CG and extends in the left-right direction of the aircraft 11. The vertical stabilizer 11B provides the aircraft 11 with stability around the yaw axis Oz, i.e., in the left-right direction. The yaw axis Oz is an axis that passes through the aircraft 11's center of gravity CG and extends in the up-down direction of the aircraft 11. The yaw axis Oz and the pitching axis Oy are perpendicular to each other. The axis perpendicular to both the yaw axis Oz and the pitching axis Oy is the roll axis Ox. The rolling axis Ox is an axis that passes through the center of gravity CG of the airframe 11 and extends in the fore-and-aft direction of the airframe 11.

[0009] The main rotor 12 is a rotating body including a plurality of rotor blades 12A. The main rotor 12 is rotatably mounted on the upper part of the airframe 11 via a rotor mast 12B. The number of rotor blades 12A is N, for example, four. The main rotor 12 is driven by a drive source mounted on the airframe 11. The drive source is, for example, an engine. The main rotor 12 generates lift that supports the weight of the rotary-wing aircraft 10 and thrust that overcomes air resistance and moves forward. A central axis of rotation O1 of the main rotor 12 passes, for example, through or near the center of gravity CG of the airframe 11. The central axis of rotation O1 may coincide with the yawing axis Oz.

[0010] The tail rotor 13 is a rotor including multiple rotor blades 13A and is provided at the rear of the airframe 11. The tail rotor 13 is rotatably attached, for example, to the right side of the vertical stabilizer 11B. The central axis O2 of rotation of the tail rotor 13 is, for example, perpendicular to the central axis O1 of rotation of the main rotor 12. When the rotary-wing aircraft 10 flies forward, a torque acts on the airframe 11 in a direction opposite to the rotation direction of the main rotor 12 due to a reaction to the rotation of the main rotor 12. The tail rotor 13 generates a force in a direction opposite to the torque, thereby suppressing rotation of the airframe 11 in a direction opposite to the rotation direction of the main rotor 12.

[0011] <Vibration of Airframe 11> The main rotor 12 is a source of vibration in the rotary-wing aircraft 10. For example, when a rotary-wing aircraft 10 having N rotor blades 12A flies forward, a particularly large vibratory load acts on the rotary-wing aircraft 10 with a period (N / rev) that is N times the rotation period of the main rotor 12. The large vibratory load on the main rotor 12 directly leads to an increase in the vibration felt by the crew of the rotary-wing aircraft 10. Such vibration of the airframe 11 is closely related to a dynamic stall that occurs in the rotor blades 12A. Therefore, the magnitude of vibration of the airframe 11 can be considered based on the degree of dynamic stall.

[0012] Dynamic stall is a phenomenon in which hysteresis occurs in lift when the angle of attack α of the rotor blade 12A exceeds the static stall angle and causes a pitching oscillation. The angle of attack α is the tilt angle of an object relative to the direction of fluid flow. The fluid is air, and the object is the rotor blade 12A. The stall angle is the angle of attack α at which the lift coefficient CL of the rotor blade 12A is maximized. The lift coefficient CL represents the lift generated on an object relative to the density and velocity of the fluid flowing around the object and the surface area on which the lift acts. The lift coefficient CL is a dimensionless quantity.

[0013] A dynamic stall is particularly likely to occur in the retreating rotor blade 12 A among the multiple rotor blades 12 A. The retreating rotor blade 12 A is a rotor blade 12 A that moves in a direction from the front to the rear of the airframe 11.

[0014] In a rotary-wing aircraft 10 in forward flight, the retreating rotor blade 12A of the main rotor 12 has a large angle of attack α. Therefore, for example, under conditions of heavy load and high speed, the angle of attack α may temporarily exceed the static stall angle. However, stall does not occur immediately, and high lift is often obtained. However, if the rotor blade 12A stalls, not only does it reduce the lift-to-drag ratio but also causes large fluctuations in the pitching moment, significantly reducing controllability and flight performance. Such a stall of the rotor blade 12A is a typical example of a dynamic stall.

[0015] As shown in FIG. 2 , an example of the relationship between the angle of attack α and the lift coefficient CL is shown by the first characteristic line L1. The lift coefficient CL gradually increases as the angle of attack α of the rotor blade 12A increases and reaches a first peak near the stall angle. The stall angle is, for example, around 10°. After the angle of attack α reaches the stall angle, the lift coefficient CL gradually decreases with increasing angle of attack α. This state is called stall. Thereafter, for example, if the angle of attack α gradually decreases, the lift coefficient CL gradually increases as the angle of attack α decreases and reaches a second peak at a specific angle of attack α. The second peak is larger than the first peak. After the lift coefficient CL reaches the second peak, the lift coefficient CL gradually decreases as the angle of attack α decreases. However, depending on the rotation speed of the main rotor 12 or the maximum value of the angle of attack α, the change characteristic of the lift coefficient CL with respect to the change in the angle of attack α may behave differently from the first characteristic line L1 in FIG. 2 .

[0016] The lift coefficient CL has a hysteresis characteristic with respect to changes in the angle of attack α of the rotor blade 12A. When the angle of attack α is equal to or less than the stall angle, the hysteresis width Wh is nonexistent or is small and substantially constant. When the angle of attack α exceeds the stall angle, the hysteresis width Wh increases rapidly. A rapid increase in the hysteresis width Wh indicates the occurrence of a dynamic stall. In the range of the angle of attack α where a dynamic stall occurs, the energy required for the rotorcraft 10 to fly, in other words, the energy required to generate the lift necessary for the rotorcraft 10 to fly, increases. In other words, in the range of the angle of attack α where a dynamic stall occurs, there is a large loss of energy, resulting in inefficiency.

[0017] <Aileron> In this embodiment, the following configuration is employed for the rotary-wing aircraft 10 in order to suppress vibration of the airframe 11 due to dynamic stall.

[0018] As shown in FIG. 1 , the rotorcraft 10 has an aileron 14. The aileron 14 is provided on at least a portion of the fuselage 11 other than the door where rigidity can be ensured. The aileron 14 is, for example, a plate-like body having a teardrop-shaped cross section. The teardrop shape has a rounded leading edge and a sharply pointed trailing edge. When viewed from above the fuselage 11, the aileron 14 has, for example, a rectangular outline. The aileron 14 is attached to the side of the fuselage 11. The side includes the port and starboard sides of the fuselage 11. The long side of the aileron 14 extends along the pitching axis Oy. The short side of the aileron 14 extends along the rolling axis Ox.

[0019] The ailerons 14 are provided on the port or starboard side of the airframe 11 depending on the rotation direction of the main rotor 12. When the rotation direction of the main rotor 12 is counterclockwise as viewed from above the airframe 11, the ailerons 14 are provided on the port front part of the airframe 11. When the rotation direction of the main rotor 12 is clockwise as viewed from above the airframe 11, the ailerons 14 are provided on the starboard front part of the airframe 11.

[0020] The port front or starboard front of the airframe 11 is the portion of the port or starboard side of the airframe 11 that is located forward of the center of gravity CG. The center of gravity CG is set, for example, below the rotor mast 12B to ensure stable flight of the rotary-wing aircraft 10. Therefore, the port front or starboard front of the airframe 11 is also the portion of the port or starboard side of the airframe 11 that is forward of the rotor mast 12B or the central axis of rotation O1 of the main rotor 12.

[0021] 1 , the rotation direction of the main rotor 12 is counterclockwise when viewed from above the airframe 11. The aileron 14 is disposed near the top of the port front portion of the airframe 11. When the rotorcraft 10 flies forward, the aileron 14 generates lift on the port front portion of the airframe 11. The lift is an upward force on the airframe 11.

[0022] The lift generated by the aileron 14 generates a moment around the pitching axis Oy in a direction that tilts the nose of the aircraft 11 upward, and a moment around the rolling axis Ox in a direction that tilts the aircraft 11 to the right. That is, the lift generated by the aileron 14 acts in a direction that tilts the nose of the aircraft 11 upward and left, in other words, in a direction that tilts the tail of the aircraft 11 downward and rearward to the right. As a result, the pitch angle of the aircraft 11 increases, and the lift of the aircraft 11 also increases. As a result, the average value of the angle of attack α decreases. The degree of dynamic stall also decreases.

[0023] As shown in Figure 2, the relationship between the angle of attack α and the lift coefficient CL in this case is as indicated by the second characteristic line L2. That is, the lift coefficient CL gradually increases and reaches a peak as the angle of attack α of the rotor blade 12A increases. After the angle of attack α reaches its peak, for example, if the angle of attack α decreases, the lift coefficient CL gradually decreases as the angle of attack α decreases. The hysteresis width Wh does not exist or is small and substantially constant. There is no region of the angle of attack α where the hysteresis width Wh increases sharply, i.e., there is no region of the angle of attack α where a dynamic stall occurs.

[0024] When the rotation direction of the main rotor 12 is clockwise as viewed from above the airframe 11, the aileron 14 is disposed in a position close to the upper part of the front starboard part of the airframe 11. When the rotary-wing aircraft 10 flies forward, the aileron 14 generates lift on the front starboard part of the airframe 11. The lift is an upward force acting on the airframe 11.

[0025] The lift generated by the aileron 14 generates a moment around the pitching axis Oy in a direction that tilts the nose of the aircraft 11 upward, and a moment around the rolling axis Ox in a direction that tilts the aircraft 11 to the left. That is, the lift generated by the aileron 14 acts in a direction that tilts the nose of the aircraft 11 up and to the right, in other words, in a direction that tilts the tail of the aircraft 11 downward and rearward to the left. As a result, the pitch angle of the aircraft 11 increases, and the lift of the aircraft 11 also increases. As a result, the average value of the angle of attack α decreases. The degree of dynamic stall also decreases.

[0026] <Effects of this embodiment> According to this embodiment, the following effects can be obtained. (1) The rotary-wing aircraft 10 has an airframe 11 and a main rotor 12 provided on the upper part of the airframe 11. The main rotor 12 rotates in a counterclockwise or clockwise direction when viewed from above the airframe 11. The rotary-wing aircraft 10 has an aileron 14 provided on the airframe 11. The aileron 14 is provided on the port front part of the airframe 11 when the rotation direction of the main rotor 12 is counterclockwise. The aileron 14 is provided on the starboard front part of the airframe 11 when the rotation direction of the main rotor 12 is clockwise.

[0027] When the aileron 14 is provided on the port front of the aircraft 11, the lift generated by the aileron 14 acts in a direction that tilts the aircraft 11 downward and rearward to the right. This makes it possible to suppress the occurrence of a dynamic stall. By suppressing the occurrence of a dynamic stall, it is possible to suppress vibration of the aircraft 11. It is also possible to suppress the loss of energy required for the rotorcraft 10 to fly, thereby increasing efficiency.

[0028] When the aileron 14 is provided on the front starboard side of the aircraft 11, the lift generated by the aileron 14 acts in a direction that tilts the aircraft 11 downward and rearward to the left. This makes it possible to suppress the occurrence of a dynamic stall. By suppressing the occurrence of a dynamic stall, it is possible to suppress vibration of the aircraft 11. It is also possible to suppress the loss of energy required for the rotorcraft 10 to fly, thereby improving efficiency.

[0029] (2) The rotary-wing aircraft 10 has a rotor mast 12B. The rotor mast 12B is provided on the upper part of the airframe 11 and rotatably supports the main rotor 12. The port front or starboard front of the airframe 11 is the port or starboard portion of the airframe 11 located forward of the rotor mast 12B. With this configuration, when the aileron 14 is provided on the port front of the airframe 11, the lift generated by the aileron 14 can be appropriately applied in a direction that tilts the airframe 11 downward and rearward to the right. Furthermore, when the aileron 14 is provided on the starboard front of the airframe 11, the lift generated by the aileron 14 can be appropriately applied in a direction that tilts the airframe 11 downward and rearward to the left.

[0030] (3) The ailerons 14 are disposed at a position close to the upper part of the aircraft 11 at the front port side or front starboard side of the aircraft 11. A position close to the upper part of the aircraft 11 may not get in the way of crew members getting on and off. A position close to the upper part of the aircraft 11 is suitable as an installation space for the ailerons 14.

[0031] Furthermore, when the main rotor 12 generates upward lift against the gravity of the airframe 11, downwash is generated below the plane of rotation of the main rotor 12. Downwash is a strong downward wind blowing down from the main rotor 12. The speed of the downwash increases the further downward from the plane of rotation of the main rotor 12. For this reason, the higher the aileron 14 is attached to the side of the airframe 11, the better. For example, the aileron 14 may be provided so that the upper surface of the aileron 14 smoothly connects to the upper surface of the airframe 11. The closer the aileron 14 is to the plane of rotation of the main rotor 12, the less the aileron 14 is affected by downwash. From this perspective, a position close to the top of the airframe 11 is an ideal space for installing the aileron 14.

[0032] (4) The number of main rotors 12 is one. In a so-called single-rotor type rotary-wing aircraft 10, the ailerons 14 are particularly effective in reducing vibrations of the airframe 11. (5) It is only necessary to provide the ailerons 14 to the airframe 11 while leaving the main rotor 12 in place. Therefore, vibrations of the airframe 11 can be suppressed with a simple configuration.

[0033] Other Embodiments This embodiment may be modified as follows: The attachment angle of the aileron 14 with respect to the side of the fuselage 11 may be set appropriately depending on the specifications of the rotary-wing aircraft 10, etc.

[0034] The amount by which the ailerons 14 protrude from the side of the fuselage 11 may be set as appropriate depending on the specifications of the rotary-wing aircraft 10. The attachment position of the ailerons 14 relative to the port front or starboard front of the fuselage 11 may be set as appropriate depending on the specifications of the rotary-wing aircraft 10. For example, as shown by the two-dot chain line in FIG. 1 , the ailerons 14 may be positioned closer to the bottom of the fuselage 11 rather than closer to the top. A position closer to the bottom of the fuselage 11 may also not interfere with passenger boarding and disembarking. In this case, however, the following points must be taken into consideration. That is, as described above, the downwash velocity increases the further downward from the plane of rotation of the main rotor 12. Therefore, the higher the attachment position of the ailerons 14 relative to the side of the fuselage 11, the better. The closer the ailerons 14 are to the plane of rotation of the main rotor 12, the less the ailerons 14 are affected by downwash.

[0035] As shown in FIG. 3 , the aileron 14 may have a flaperon 14A. The flaperon 14A is a portmanteau of a flap and an aileron. The flaperon 14A is a type of high-lift device and is a moving wing that functions as both a flap and an aileron. The flaperon 14A is provided, for example, at the aft end of the aileron 14. This makes it possible to generate a predetermined amount of lift regardless of the attitude angle of the aircraft 11. While FIG. 3 shows an example in which the aileron 14 is disposed below the aircraft 11, the same applies when the aileron 14 is disposed above the aircraft 11.

[0036] As shown in FIG. 4 , the aileron 14 may have a rescue hoist 14B. The rescue hoist 14B is a rescue hoist, a type of winch. The rescue hoist 14B hoists and lowers a load via a wire 14C. A hook 14D, for example, is attached to the tip of the wire 14C. For example, in mountainous areas where the rotorcraft 10 cannot land or during water rescue operations, the wire 14C is extended while the rotorcraft 10 is hovering in the air. This allows, for example, a rescuer or a rescue stretcher to be lowered. The hook 14D may have a mechanism to prevent it from coming loose. While FIG. 4 shows an example in which the aileron 14 is located at the bottom of the airframe 11, the same applies when the aileron 14 is located at the top of the airframe 11.

[0037] 4, the interior of the aileron 14 may be configured to function as a fuel tank 14E. In this way, fuel can be stored inside the aileron 14. <Additional Notes> The rotorcraft described in this embodiment can be understood, for example, as follows.

[0038] 1. A rotary-wing aircraft (10) according to a first aspect has an airframe (11) and a main rotor (12) provided on an upper portion of the airframe (11), the main rotor (12) being configured to rotate in a counterclockwise or clockwise direction when viewed from above the airframe (11), and has an aileron (14) provided on the airframe (11), the aileron (14) being provided on the port front portion of the airframe (11) when the rotation direction of the main rotor (12) is counterclockwise, and the aileron (14) being provided on the starboard front portion of the airframe (11) when the rotation direction of the main rotor (12) is clockwise.

[0039] In the rotary-wing aircraft according to the first aspect, when the ailerons are provided on the port front or starboard front of the aircraft, the lift generated by the ailerons acts in a direction that tilts the aircraft downward and rearward to the right or left. As a result, the center of gravity of the aircraft moves to the starboard rear or port rear of the aircraft when viewed from above. This makes it possible to suppress the occurrence of dynamic stall. By suppressing the occurrence of dynamic stall, it is possible to suppress vibration of the aircraft.

[0040] 2. A rotary-wing aircraft (10) according to a second aspect is the rotary-wing aircraft (10) according to the first aspect, further comprising a rotor mast (12B) provided on an upper portion of the fuselage (11), the rotor mast (12B) being configured to rotatably support the main rotor (12), and the port front or starboard front part of the fuselage (11) is the port side part or starboard side part of the fuselage (11) located forward of the rotor mast (12B).

[0041] According to the rotary-wing aircraft of the second aspect, the lift generated by the aileron can be appropriately applied in a direction that tilts the aircraft downward and rearward to the right or downward and rearward to the left. 3. The rotary-wing aircraft (10) of the third aspect is the rotary-wing aircraft (10) of the first or second aspect, in which the aileron (14) is arranged in a position close to the upper or lower part of the aircraft (11) at the front port or front starboard side of the aircraft (11).

[0042] As in the rotorcraft according to the third aspect, a position near the upper or lower part of the aircraft may not be an obstacle when crew members get on or off. A position near the upper or lower part of the aircraft is also suitable as space for installing an aileron.

[0043] 4. A rotorcraft (10) according to a fourth aspect is the rotorcraft (10) of any one of the first to third aspects, wherein the aileron (14) has a flaperon (14A) which is one of high-lift devices.

[0044] According to the rotorcraft of the fourth aspect, a predetermined lift force can be generated regardless of the attitude angle of the aircraft. 5. According to the rotorcraft (10) of the fifth aspect, in the rotorcraft (10) of any one of the first to third aspects, the aileron (14) has a rescue winch (14B) configured to hoist and lower a load via a wire (14C).

[0045] According to the rotary-wing aircraft of the fifth aspect, during rescue, the load can be hoisted up and down by the winch while the rotary-wing aircraft is stopped in the air. 6. The rotary-wing aircraft (10) of the sixth aspect is the rotary-wing aircraft (10) of any one of the first to third aspects, wherein the inside of the aileron (14) is configured to function as a fuel tank.

[0046] According to the rotorcraft of the sixth aspect, fuel can be stored inside the aileron. 7. A rotorcraft (10) of the seventh aspect is the rotorcraft (10) of any one of the first to fifth aspects, in which the number of the main rotors is one.

[0047] According to the rotary-wing aircraft of the seventh aspect, the effect of reducing vibration of the airframe by the ailerons is particularly high in so-called single-rotor type rotary-wing aircraft.

Claims

1. A rotary-wing aircraft having an airframe and a main rotor mounted on top of the airframe, the main rotor configured to rotate counterclockwise or clockwise when viewed from above the airframe, and an aileron mounted on the airframe, the aileron being mounted on the port front of the airframe when the rotation direction of the main rotor is counterclockwise, and the aileron being mounted on the starboard front of the airframe when the rotation direction of the main rotor is clockwise.

2. A rotary-wing aircraft according to claim 1, comprising a rotor mast provided on the upper part of the aircraft and configured to rotatably support the main rotor, and wherein the port front or starboard front part of the aircraft is the port part or starboard part of the aircraft located forward of the rotor mast.

3. A rotary-wing aircraft according to claim 1 or claim 2, wherein the aileron is positioned at a position close to the upper or lower part of the aircraft on the port or starboard front side.

4. A rotorcraft according to claim 1 or 2, wherein the aileron has a flaperon, which is a type of high-lift device.

5. A rotorcraft according to claim 1 or claim 2, wherein the aileron has a rescue winch configured to hoist and lower a load via a wire.

6. A rotorcraft according to claim 1 or 2, wherein the inside of the aileron is configured to function as a fuel tank.

7. A rotary-wing aircraft according to claim 1 or claim 2, wherein the number of the main rotors is one.

Images