A design method of fairing for low-drag trailing edge flap actuation mechanism of transport aircraft
By designing a fairing for transport aircraft, the performance loss problem of the flap actuation mechanism during the cruise phase was solved, thus protecting the actuation mechanism and improving the aircraft's cruise performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAN AIRCRAFT DESIGN INST OF AVIATION IND OF CHINA
- Filing Date
- 2026-05-06
- Publication Date
- 2026-07-14
Smart Images
Figure CN122126468B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of aircraft structural design, and specifically relates to a fairing design method for a low-drag trailing edge flap actuation mechanism of a transport aircraft. Background Technology
[0002] Trailing-edge flaps increase wing area and alter wing camber, primarily enhancing lift or drag during takeoff and landing to improve performance. During takeoff, the flaps deflect downwards and rearwards at a smaller angle, mainly increasing lift and helping the aircraft achieve a safe takeoff speed more quickly. During landing, the flaps deflect downwards and rearwards at a larger angle, significantly increasing both lift and drag, helping to reduce landing speed and shorten landing distance. Trailing-edge flaps are mounted on the trailing edge of the wing and operate by deflecting downwards or sliding backwards. Transport aircraft often use trailing-edge flaps, which can be categorized into single-slotted, double-slotted, and triple-slotted flaps depending on the aircraft's performance requirements.
[0003] The trailing edge flaps are deflected via an actuation mechanism, which includes a drive screw and flap rails. Due to space constraints in the wing structure, this actuation mechanism is mounted on the outside of the wing. If it were directly exposed to the air without a fairing, it would result in significant performance loss for the transport aircraft during the cruise phase. Therefore, a low-drag fairing needs to be designed to protect the flap actuation mechanism and prevent it from being directly exposed to high-speed airflow. Summary of the Invention
[0004] To address the aforementioned problems, this application provides a fairing design method for a low-drag trailing edge flap actuation mechanism of a transport aircraft, mainly comprising:
[0005] Step S1: Determine the maximum half-width line and the lower zero line that meet the spatial safety requirements of the actuator;
[0006] Step S2: Between the maximum half-width line and the lower zero longitudinal line, multiple characteristic profile boundary lines are formed at different heading stations. The tangent vector at the intersection of the boundary line and the lower zero longitudinal line is set to be perpendicular to the symmetry plane of the cover. The tangent vector at the intersection of the boundary line and the maximum half-width line is set to have an outward tilt angle with the symmetry plane of the cover. The outward tilt angle gradually decreases to 0° in the reverse heading direction of the maximum half-width line.
[0007] Step S3: Using the maximum half-width line, the lower zero longitudinal line, and each feature section as the linear framework of the main body of the cover, the outer geometric shape of the main body of the cover is generated by using the surface lofting method. The outer side refers to the side away from the fuselage with the symmetry plane of the cover as the dividing plane.
[0008] Step S4: Mirror the outer geometry to generate the inner geometry of the main body of the cover. Extend the inner geometry to intersect with the lower surface of the wing by using an extended curved surface.
[0009] Step S5: Using the specified end plane as a tangent constraint, create a semi-cylindrical surface with a specified radius. Set a flat tail section of the cover between the semi-cylindrical surface and the main body of the cover. With the smoothness of the tail control line of the tail section as the optimization target, cut the semi-cylindrical surface to form the end cylindrical surface.
[0010] Preferably, step S1 further includes:
[0011] Step S11: Using the horizontal plane of the canopy structure as the reference plane, the maximum width plane as the width constraint, and the starting plane of the canopy as the starting constraint, design the theoretical maximum half-width line that meets the spatial safety requirements of the actuation mechanism. Stretch the theoretical maximum half-width line along the direction perpendicular to the horizontal plane of the canopy structure until it intersects with the lower wing surface, and take the intersection line as the maximum half-width line.
[0012] Step S12: Using the symmetry plane of the cover as the reference plane and the starting plane of the cover as the initial constraint, design the lower zero longitudinal line that meets the spatial safety requirements of the actuation mechanism.
[0013] Preferably, meeting the space safety requirements of the actuation mechanism means that the gap between the theoretical maximum half-width line or the lower zero longitudinal line and the actuation mechanism inside the fairing is not less than 1 inch.
[0014] Preferably, in step S2, the boundary line of the feature profile is a conic section of the second degree, and the value of its type factor f is in the range of 0.5 to 0.85.
[0015] Preferably, in step S2, along the reverse direction, eight stations with length percentages of 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, and 0.75 are selected on the lower zero longitudinal line to construct the boundary lines of eight characteristic profiles. The outward inclination angle of the characteristic profile boundary line at station 0.01 is the largest, and the outward inclination angle of the characteristic profile boundary line at station at the outer boundary plane of the main body of the cover is 0°.
[0016] Preferably, the outward inclination angle of the characteristic profile boundary line at station 0.01 is 15°, the outward inclination angle of the characteristic profile boundary line at station 0.05 is 10°, the outward inclination angle of the characteristic profile boundary line at station 0.1 is 5°, and the outward inclination angle of the characteristic profile boundary line at other stations is 0°.
[0017] Preferably, in step S5, the specified radius is 10 mm.
[0018] Preferably, step S5 further includes:
[0019] The length of the tail section of the fairing is set to not exceed 10% of the local wing chord length.
[0020] The fairing designed in this application not only protects the safety of the flap actuation mechanism, but also significantly improves the aircraft's cruise performance. Attached Figure Description
[0021] Figure 1 This is a side-plane line diagram of the flap rail fairing of a preferred embodiment of the fairing design method for the low-drag trailing edge flap actuation mechanism of transport aircraft in this application.
[0022] Figure 2 This application Figure 1 Schematic diagrams of various reference planes during the design of the fairing in the illustrated embodiment.
[0023] Figure 3 This application Figure 1 A schematic diagram of the fairing position in the embodiment shown.
[0024] Figure 4 This is a schematic diagram illustrating the station location parameters of the characteristic profile.
[0025] Among them, 1-maximum half-width line, 2-lower zero longitudinal line, 3-characteristic profile, 4-tail control line, 5-main body of the cover, 6-tail section of the cover, 7-end cylindrical surface, 8-maximum width plane, 9-symmetry plane of the cover, 10-horizontal plane of the cover structure, 11-starting plane of the cover, 12-center end plane of the main body of the cover, 13-end plane, 14-outer boundary plane of the main body of the cover, 15-inner boundary plane of the main body of the cover, 16-theoretical maximum half-width line. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.
[0027] This application provides a fairing design method for a low-drag trailing edge flap actuation mechanism of a transport aircraft, such as... Figures 1-3 As shown, it mainly includes:
[0028] Step S1: Determine the maximum half-width line 1 and the lower zero line 2 that meet the spatial safety requirements of the actuator;
[0029] Step S2: Between the maximum half-width line 1 and the lower zero longitudinal line 2, multiple characteristic profiles 3 boundary lines are formed at different heading positions. The tangent vector at the intersection of the boundary line and the lower zero longitudinal line 2 is set to be perpendicular to the symmetry plane 9 of the cover. The tangent vector at the intersection of the boundary line and the maximum half-width line 1 is set to have an outward tilt angle with the symmetry plane 9 of the cover. The outward tilt angle gradually decreases to 0° in the reverse heading direction of the maximum half-width line 1.
[0030] Step S3: Using the maximum half-width line 1, the lower zero longitudinal line 2 and each feature section 3 as the linear framework of the main body 5, the outer geometric shape of the main body 5 is generated by the surface lofting method. The outer side refers to the side away from the fuselage with the symmetry plane 9 of the cover as the dividing plane.
[0031] Step S4: Mirror the outer geometry to generate the inner geometry of the main body 5 of the cover. Extend the inner geometry to intersect with the lower surface of the wing by using an extended curved surface.
[0032] Step S5: Using the specified end plane 13 as a tangential constraint, create a semi-cylindrical surface of a specified radius. Set a flat tail section 6 between the semi-cylindrical surface and the main body 5 of the cover. With the smoothness of the tail control line 4 of the tail section 6 as the optimization target, cut the semi-cylindrical surface to form the end cylindrical surface 7.
[0033] First refer to Figure 3 It shows a wing on one side of the aircraft and a fairing designed according to this application located below the wing. The fairing contains an actuating mechanism to drive the flaps on the rear side of the wing to deflect (flap structure not shown). The portion of the fairing located below the wing is called the fairing body 5, and the portion located below the flaps is called the fairing tail section 6. The overall structure of the fairing in this application is basically symmetrical from left to right, with the side closer to the fuselage being the inner side and the side farther from the fuselage being the outer side. In steps S1-S3, this application designs a curved surface on one side of the fairing body 5. Figure 3 The dihedral wing shown here first designs the outer curved surface, while the converse is to design the inner curved surface first. Then, in step S4, a mirror image is created to obtain the other curved surface of the main body 5 of the dome. Finally, in step S5, the tail section 6 of the dome is designed. The following is a detailed description.
[0034] In step S1, it is first necessary to determine the maximum half-width line 1 and the lower zero vertical line 2.
[0035] In some alternative implementations, step S1 further includes:
[0036] Step S11: Using the horizontal plane 10 of the cover structure as the reference plane, the maximum width plane 8 as the width constraint, and the starting plane 11 of the cover as the starting constraint, design the theoretical maximum half-width line 16 that meets the space safety requirements of the actuation mechanism. Stretch the theoretical maximum half-width line 16 along the direction perpendicular to the horizontal plane 10 of the cover structure until it intersects with the lower wing surface, and take the intersection line as the maximum half-width line 1.
[0037] Step S12: Using the symmetry plane 9 of the cover as the reference plane and the starting plane 11 of the cover as the starting constraint, design the lower zero longitudinal line 2 to meet the spatial safety requirements of the actuation mechanism.
[0038] refer to Figure 2 In step S11, the maximum half-width line 1 is designed with the horizontal plane 10 of the fairing structure as the reference plane. This essentially ensures, in the width direction, that the fairing can accommodate the actuating mechanism within it and meet the spatial safety requirements of the actuating mechanism. Therefore, the starting plane 11 and the maximum width plane 8 of the fairing are introduced as constraints. The rear end of the fairing is a free end and is not constrained. In step S12, the lower zero longitudinal line 2 is designed with the symmetry plane 9 of the fairing as the reference plane. This essentially ensures, in the height direction, that the fairing can accommodate the actuating mechanism within it. The symmetry plane 9 of the fairing is typically the symmetry plane of the maximum structural width of the actuating mechanism.
[0039] In this embodiment, the NURBS curve modeling method is used to design the maximum half-width line 1 and the lower zero vertical line 2.
[0040] In some alternative implementations, meeting the space safety requirements of the actuator means that the gap between the theoretical maximum half-width line 16 or the lower zero longitudinal line 2 and the actuator inside the fairing is not less than 1 inch.
[0041] In this embodiment, the movement safety of the actuating mechanism is ensured by the gap. Figure 2 In this context, the minimum distance between the maximum width plane 8 and the mechanism is 25.4mm.
[0042] Then, in step S2, multiple feature profiles 3 are constructed, referring to... Figure 2 The feature section 3 has a boundary line used to connect the maximum half-width line 1 and the lower zero longitudinal line 2. The boundary lines of multiple feature sections 3 together with the maximum half-width line 1 and the lower zero longitudinal line 2 constitute the linear frame structure of the main body 5 of the cover.
[0043] In some optional embodiments, in step S2, the boundary line of the feature profile 3 is a conic section of the second degree, and the value of its shape factor f is in the range of 0.5 to 0.85.
[0044] In some optional embodiments, in step S2, along the reverse direction, eight stations are selected on the lower zero longitudinal line 2 with length percentages of 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.75 and the outer boundary plane 14 of the main body of the cover to construct the boundary lines of eight feature sections 3. The outward inclination angle of the boundary line of the feature section 3 at station 0.01 is the largest, and the outward inclination angle of the boundary line of the feature section 3 at station 14 of the outer boundary plane of the main body of the cover is 0°.
[0045] In this embodiment, firstly... Figure 2 The three end planes of the main body of the canopy are explained. Due to the sweep-back design of the trailing edge of the wing, the end plane of the main body of the canopy 5 is not perpendicular to the heading direction, but has a certain angle. This makes the center and the two sides of the end of the main body of the canopy 5 not the same plane. Therefore, three reference planes are designed here: the center end plane 12 of the main body of the canopy, the outer boundary plane 14 of the main body of the canopy, and the inner boundary plane 15 of the main body of the canopy.
[0046] In this embodiment, stations with different length percentages are selected on the lower zero longitudinal line 2. This essentially means selecting stations between the starting plane 11 and the ending plane 12 of the main body of the cover, either along the heading or counter-heading direction. However, the very last station should be constrained by the outer boundary plane 14 of the main body of the cover. Taking the counter-heading direction as an example, for instance… Figure 4 As shown, a total of eight stations are formed, thereby enabling the construction of the boundary lines of eight characteristic profiles 3. In alternative embodiments, other stations may also be selected, taking into account the structural width characteristics of the actuating mechanisms within the fairing.
[0047] In some optional embodiments, the outward inclination angle of the boundary line of feature section 3 at station 0.01 is 15°, the outward inclination angle of the boundary line of feature section 3 at station 0.05 is 10°, the outward inclination angle of the boundary line of feature section 3 at station 0.1 is 5°, and the outward inclination angle of the boundary line of feature section 3 at other stations is 0°.
[0048] refer to Figure 4 The angle parameters 15°, 10°, 5° and 0° are typical settings for the quadratic curve of the characteristic profile. These angle parameters are related to the hood's rectification space requirements and the hood's smoothness. In actual cases, other angle parameters can be selected according to requirements.
[0049] Then, in step S4, the inner geometric shape of the main body 5 of the cover is obtained through mirroring.
[0050] It should be noted that, in addition to the non-strict symmetry of the inner and outer sides of the fairing caused by the sweepback design of the wing trailing edge, the inconsistent height of the lower wing surface also leads to the non-strict symmetry of the inner and outer sides of the fairing. For anhedral wings, the wingtip is closer to the ground. That is, after designing the outer geometry of the fairing body 5 that fits with the lower wing surface in step S3, the inner geometry of the fairing body 5 formed after mirror symmetry design does not fit with the lower wing surface. This is why the outer geometry needs to be designed first for anhedral wings. After mirroring, there is a gap between the inner geometry and the lower wing surface. By using the extended curved surface method, the inner curved surface is extended until it completely intersects with the lower wing surface, and then the lower wing surface is used to trim the curved surface. Similarly, because the wing trailing edge is swept back, the symmetrical inner curved surface exceeds the wing trailing edge. Therefore, the inner boundary plane 15 of the fairing body is used to trim the excess part to obtain the final inner curved surface. Then, the inner and outer curved surfaces are merged into the fairing body 5.
[0051] Finally, in step S5, the design of the tail section 6 of the fairing and the end cylindrical surface is carried out.
[0052] The most prominent feature of the tail section 6 of the cover is its flat shape. First, on the horizontal plane 10 of the cover structure, a semicircular arc of a specified radius is drawn with the end plane 13 as a tangential constraint. In some optional embodiments, the specified radius in step S5 is 10mm. Then, the semicircular arc is stretched vertically to generate a semi-cylindrical surface. This semi-cylindrical surface is appropriately trimmed, and the trimming amount is iteratively adjusted based on the smoothness of the tail control line 4, finally obtaining the end cylindrical surface 7. This end cylindrical surface 7 is used as the tangent vector input to ensure a smooth transition between the tail control line 4 and the main body 5 of the cover.
[0053] It should also be noted that, depending on the different flap deflection angles and the deflection capability of the flap actuation mechanism, in order to prevent the tail section 6 of the fairing from colliding with the flaps during the downward deflection of the fairing, the length of the tail section 6 needs to be limited. This mainly refers to limiting the distance between the center end plane 12 and the end plane 13 of the fairing body, such as not exceeding 600mm. In some optional embodiments, step S5 further includes: setting the length of the tail section 6 of the fairing to not exceed 10% of the local wing chord length.
[0054] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A fairing design method for a low-drag trailing edge flap actuation mechanism of a transport aircraft, characterized in that, include: Step S1: Determine the maximum half-width line (1) and the lower zero line (2) that meet the spatial safety requirements of the actuator. Step S2: Between the maximum half-width line (1) and the lower zero longitudinal line (2), multiple characteristic profiles (3) boundary lines are formed at different heading positions. The tangent vector at the intersection of the boundary line and the lower zero longitudinal line (2) is set to be perpendicular to the symmetry plane (9) of the cover. The tangent vector at the intersection of the boundary line and the maximum half-width line (1) is set to have an outward tilt angle with the symmetry plane (9) of the cover. The outward tilt angle gradually decreases to 0° with the reverse heading direction of the maximum half-width line (1). Step S3: Using the maximum half-width line (1), the lower zero longitudinal line (2) and each feature section (3) as the linear frame structure of the main body of the cover (5), the outer geometric shape of the main body of the cover (5) is generated by using the surface lofting method. The outer side refers to the side away from the fuselage with the symmetry plane (9) of the cover as the dividing plane. Step S4: Mirror the outer geometry to generate the inner geometry of the cover body (5). Extend the inner geometry to intersect with the lower surface of the wing by using the extended curved surface method. Step S5: Using the specified end plane (13) as the tangential constraint, make a semi-cylindrical surface with a specified radius. Set a flat tail section (6) between the semi-cylindrical surface and the main body (5). With the smoothness of the tail control line (4) of the tail section (6) as the optimization target, cut the semi-cylindrical surface to form the end cylindrical surface (7).
2. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 1, characterized in that, Step S1 further includes: Step S11: Using the horizontal plane (10) of the cover structure as the reference plane, the maximum width plane (8) as the width constraint, and the starting plane (11) of the cover as the starting constraint, design the theoretical maximum half-width line (16) that meets the space safety requirements of the actuation mechanism. Stretch the theoretical maximum half-width line (16) along the direction perpendicular to the horizontal plane (10) of the cover structure until it intersects with the lower wing surface. Take the intersection line as the maximum half-width line (1). Step S12: Using the symmetry plane (9) of the cover as the reference plane and the starting plane (11) of the cover as the starting constraint, design the lower zero longitudinal line (2) that meets the spatial safety requirements of the actuation mechanism.
3. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 2, characterized in that, The requirement to meet the space safety requirements of the actuator means that the gap between the theoretical maximum half-width line (16) or the lower zero line (2) and the actuator inside the fairing is not less than 1 inch.
4. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 1, characterized in that, In step S2, the boundary line of the feature profile (3) is a conic section of the second conic section, and the value of its type factor f is 0.5~0.
85.
5. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 1, characterized in that, In step S2, along the reverse direction, eight stations with length percentages of 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.75 and the outer boundary plane (14) of the main body of the cover are selected on the lower zero longitudinal line (2) to construct the boundary lines of eight characteristic profiles (3). The outward inclination angle of the boundary line of the characteristic profile (3) at station 0.01 is the largest, and the outward inclination angle of the boundary line of the characteristic profile (3) at station 14 of the main body of the cover is 0°.
6. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 5, characterized in that, The outward inclination angle of the boundary line of the characteristic profile (3) at station 0.01 is 15°, the outward inclination angle of the boundary line of the characteristic profile (3) at station 0.05 is 10°, the outward inclination angle of the boundary line of the characteristic profile (3) at station 0.1 is 5°, and the outward inclination angle of the boundary line of the characteristic profile (3) at other stations is 0°.
7. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 1, characterized in that, In step S5, the radius is specified as 10mm.
8. The fairing design method for the low-drag trailing edge flap actuation mechanism of a transport aircraft according to claim 1, characterized in that, Step S5 further includes: The length of the tail section (6) of the fairing is set to not exceed 10% of the local wing chord.