A method for designing a variable-sweep wing stealth aircraft afterbody canted delta configuration

Abstract

The application relates to a variable sweep wing stealth aircraft afterbody wedge shape design method, and belongs to the field of aircraft general design and stealth technology. The application is simple and practical in shape; comprehensive design factors are considered, and comprehensive requirements such as variable tail wing rotation, component coupling, stealth principle and aerodynamic resistance are covered; design constraints can be accurately converted into geometric design; variable tail wing rotation, the stealth principle, aerodynamic resistance and component coupling can be effectively converted into afterbody wedge shape point position and line tangent vector control design to be realized; the fusion design of the afterbody wedge and the surrounding curved surface is better realized; under the premise of guaranteeing the variable tail wing rotation space requirement and the binary nozzle requirement, the aerodynamic and stealth shape integration design of the afterbody wedge shape is realized. The application is mainly applied to the scheme design of the afterbody wedge shape of the variable tail wing. The method is novel, ingenious and compact in structure, has strong applicability, has a wide application range, and has a wide application prospect in the design of military aircraft.

Description

Technical Field

[0001] This invention belongs to the field of aircraft overall design and stealth technology, specifically relating to a method for designing the wedge-shaped rear fuselage of a variable-sweep wing stealth aircraft. Background Technology

[0002] In the design of the variable tail for a variable-sweep wing stealth aircraft, the V-tail has two axes of rotation. The main axis is parallel to the X-axis and is mainly responsible for the deflection control of the tail. The secondary axis is parallel to the Y-axis and is mainly responsible for the pitch control of the tail. With the main and secondary axes controlled simultaneously, the functions of the horizontal and vertical tails of traditional aircraft are realized. The variable tail adopts a suspension structure without openings, which eliminates the strong scattering vertical sidewalls and the gaps in the variable tail's straight-axis structure from affecting lateral stealth.

[0003] Since the variable tail and the two-dimensional nozzle occupy the same space, they need to be designed as a single unit. Strict control must be exercised over the shape of components that emit strong lateral scattering, ensuring a smooth aircraft surface and minimizing scattering sources. Therefore, to maintain lateral stealth performance when the variable tail deflects, an integrated stealth shape design for the fuselage wedge between the variable tail and the two-dimensional nozzle is necessary. This aft fuselage wedge design needs to address the following four issues:

[0004] 1) The RCS scattering of the rear wedge itself is controllable;

[0005] 2) The RCS coupling scattering between the rear wedge and surrounding components is controllable;

[0006] 3) The rear wedge needs to take into account stealth RCS and aerodynamic drag requirements to achieve integrated aerodynamic stealth optimization design;

[0007] 4) The rear wedge must meet the design requirements of a two-dimensional nozzle.

[0008] To address the above issues, only targeted design of the aft body wedge can properly resolve the problems and effectively control its impact on aircraft aerodynamic drag, stealth RCS scattering, and engine nozzles, thereby ensuring the successful achievement of the overall aircraft's stealth and aerodynamic performance targets. Summary of the Invention

[0009] This invention mainly targets the wedge between the variable tail fin and the two-dimensional nozzle, and provides a design method for the aft body wedge that meets the requirements of stealth, aerodynamics, and two-dimensional nozzle, so that its impact on the aircraft's aerodynamic drag and stealth RCS scattering value is minimized and controllable.

[0010] The technical solution of this invention to solve the key technical problem is:

[0011] To eliminate the negative impact of a straight-axis variable tail on the lateral stealth characteristics of an aircraft, and to adopt a dual-axis suspended tail, this invention proposes a method for designing the wedge-shaped rear fuselage of a variable-sweep wing stealth aircraft. The steps are as follows:

[0012] Step 1: Determine the boundary of the posterior wedge construction.

[0013] 1.1) Determination of the transverse boundary of the upper front end

[0014] Within the plane A containing the auxiliary shaft of the variable tail and the Z-direction, the rotation radius R1 of the variable tail determines the highest point of the rotating ball in the Z-direction as the upper left limit point a1; within the plane A, the right limit point a2 is selected within the cross-sectional line of the upper part of the fuselage, forming the lateral boundary a1a2 of the upper front end of the rear wedge.

[0015] 1.2) Determination of the lower front transverse boundary

[0016] Within plane A, where the auxiliary shaft of the variable tail fin is located and the Z-direction is located, the lowest point of the rotating ball in the Z-direction is determined as the lower left limit point b1; within plane A, the right limit point b2 is selected within the cross-sectional line of the lower part of the fuselage, forming the lateral boundary b1b2 of the lower front end of the rear wedge.

[0017] 1.3) Determination of the rear lateral boundary and the outermost boundary

[0018] The short side of the binary nozzle is H1. A straight line K1 parallel to the Y-axis is drawn through the midpoint of the upper and lower vertices of the rear end of the binary nozzle. The right extreme point of the rear transverse boundary is located on the straight line K1. A plane B is drawn through the upper root endpoint n1 of the binary nozzle outlet, the projection of the inner side line of the horizontal tail in the XY plane, and the Z-axis. The intersection of plane B and K1 forms the right extreme point c1 of the rear transverse boundary.

[0019] Based on the parallel principle of the two-dimensional nozzle and the variable tail fin, the variable tail fin rotates outward and translates the variable tail fin safety distance H2, intersecting the plane A with the line P. Take the point c2 where the maximum value in the Y direction is located, and draw the line of symmetry with the inner side line of the horizontal tail through point c2, the plane C containing the Z axis and the boundary line K2.

[0020] Draw plane D, which is formed by the projection of the nozzle boundary onto the XY plane and the Z-axis. Draw plane E, which is parallel to plane D, through point n1. Plane E intersects the boundary line K2 at point c3, which is the left extreme point of the rear transverse boundary, forming the rear transverse boundary c1c3 and the outermost boundary c2c3.

[0021] 1.4) Determination of the outermost upper boundary

[0022] Through point c3, construct a plane F parallel to the ZX plane. Plane F intersects the upper curved surface of the rear fuselage at point d1. Construct a spline curve c3d1 through points c3 and d1. At point d1, the tangent tension of the curve is α1, forming the outermost upper boundary c3d1.

[0023] 1.5) Determination of the outermost lower boundary

[0024] Plane F intersects the lower curved surface of the rear fuselage at point d2. A spline curve c3d2 is drawn through points c3 and d2. At point d2, the tangent tension of the curve is α2, forming the outermost upper boundary c3d2.

[0025] 1.6) Determination of the upper inner boundary

[0026] Draw a spline curve a2n1 through points a2 and n1. The tangent tension α3 at point a2 forms the upper inner boundary a2n1. Draw a straight line through points c1 and n1 to form the inner boundary c1n1.

[0027] 1.7) Determination of the lower inner boundary

[0028] Draw a spline curve b2m1 passing through point b2 and the lower root endpoint m1 of the binary nozzle outlet. The tangent tension α4 of the curve at point b2 forms the lower inner boundary b2m1. Draw a straight line passing through points c1 and m1 to form the inner boundary c1m1.

[0029] Step 2: Determine the longitudinal control line of the posterior wedge.

[0030] 2.1) Construct the longitudinal control line of the first cross-section on the upper outer side of the two-dimensional nozzle.

[0031] Through point n1, draw plane G formed by the nozzle trailing edge line and the Z-axis. Plane G intersects c3d1 at point e1. Through points n1 and e1, draw spline curve n1e1. The spline curve is tangent to the upper trailing edge line of the nozzle. At point n1, the tangent tension of the curve is α5. Plane G intersects c2c3 at point e2. Connect e1 and e2 to form the upper lateral straight line e1e2.

[0032] 2.2) Construct the longitudinal control line of the first cross-section on the lower outer side of the two-dimensional nozzle.

[0033] Through point m1, draw plane H formed by the nozzle trailing edge line and the Z-axis. Plane H intersects c3d2 at point e3. Through points m1 and e3, draw spline curve m1e3. The spline curve is tangent to the lower trailing edge line of the nozzle. At point m1, the tangent tension of the curve is α6. Connect e2 and e3 to form the lower lateral straight line e2e3.

[0034] 2.3) Derive the actual boundary control lines based on the upper and lower lateral straight lines within the first section.

[0035] Chamfer R2 between the upper lateral line e1e2 and the lower lateral line e2e3. Take the midpoint e4 of the chamfer. Translate the upper lateral line e1e2, the lower lateral line e2e3, and the chamfer R2 from point e4 to point e2, keeping the position of edge c2c3 unchanged. Due to the change in position, the upper lateral line e1e2 evolves into line E1. Draw spline E2 through point e1, which transitions with line E1 by an arc. Draw plane I parallel to XY through e2. The angle between the upper lateral line E1 and its projection line in plane I is the lateral tilt angle θ1.

[0036] The lower lateral line e2e3 changes position and evolves into line E3. A spline E4 is drawn through point e3, transitioning to line E3 via an arc. The angle between the lower lateral line E3 and its projection line in plane I is the lateral tilt angle θ2. The chamfer R2 changes position and evolves into chamfer E5. The actual lateral boundary control line is E6, which includes E1+E2+E3+E4+E5.

[0037] 2.4) Construct the longitudinal control line of the upper second section behind the variable tail fin rotation ball.

[0038] The trailing edge of the intersection point between the variable tail fin spherical ball and the tail fin is connected to a plane J parallel to the YZ plane. Plane J intersects the straight line c3d1 and the spline c2c3 at points f1 and f2 respectively. Connecting points f1 and f2 forms the upper lateral straight line f1f2. Plane J intersects the spline a2n1 at point f3. Through points f1 and f3, draw the spline curve f1f3. At point f3, the tangent tension of the curve is α7.

[0039] 2.5) Construct the longitudinal control line of the lower second section behind the variable tail fin rotation ball.

[0040] From the trailing edge point of the intersection of the variable tail fin spherical ball and the tail fin, there is a plane K parallel to the YZ plane. The plane K intersects the spline c3d2 at point f4. Connect points f2 and f4 to form the lower lateral straight line f2f4. The plane K intersects b2m1 at point f5. Through points f4 and f5, draw the spline curve f4f5. At point f5, the tangent tension of the curve is α8.

[0041] 2.6) Derive the actual boundary control lines based on the upper and lower lateral straight lines within the second section.

[0042] Chamfer R3 between the upper lateral lines f1f2 and f2f3. Take the midpoint f6 of the chamfer. Translate the upper lateral lines f1f2, f2f3, and R3 from point f6 to point f2, keeping the position of edge c2c3 unchanged. Due to the change in position, the upper lateral lines f1f2 evolve into line F1. Draw spline F2 through point f1, which transitions with line F1 by an arc. Draw a plane L parallel to XY through f2. The angle between the upper lateral lines F1 and their projection line in plane L is the lateral tilt angle θ3.

[0043] The lower lateral line f2f3 evolves into line F3 due to a change in position. A spline F4 is drawn through point f4, transitioning to line F3 with an arc. The angle between the lower lateral line F3 and its projection line in plane L is the lateral tilt angle θ4. The chamfer R3 evolves into chamfer F5 due to a change in position. The actual lateral boundary control line is F6, which includes F1+F2+F3+F4+F5.

[0044] 2.7) Construct the internal control line between the upper part of the wedge and the transition area of ​​the fuselage.

[0045] Take the midpoint g1 of line E1 and the midpoint g2 of line F1. Draw the line g1g2. Draw a plane M parallel to the plane XY through point g2. The plane M intersects the line P at point g3. Draw the spline curve g2g3 through points g2 and g3. At point g2, the tangent tension of the curve is α9.

[0046] The intersecting line P intersects the upper transverse boundary a1a2 at point g4. Through points g4 and f1, construct the spline curve g4f1. At point f1, the tangent tension of the curve is α10.

[0047] 2.8) Construct the internal control line between the lower part of the wedge and the transition area of ​​the fuselage.

[0048] Take the midpoint h1 of line F1 and the midpoint h2 of line F2. Draw the line h1h2. Draw a plane N parallel to the plane XY through point h2. Plane N intersects the line P at point h3. Draw the spline curve h2h3 through points h2 and h3. At point h2, the tangent tension of the curve is α11. The line P intersects the lower horizontal boundary b1b2 at point h4. Draw the spline curve h4f4 through points h4 and f4. At point f4, the tangent tension of the curve is α12.

[0049] Step 3: Construct the wedge-shaped surface of the posterior body

[0050] 3.1) Construct the fusion surface of the upper part of the rear wedge

[0051] Based on the upper longitudinal control lines constructed above, the surface is constructed from front to back in a segmented form of "transition surface + ruled surface + transition surface";

[0052] 3.2) Construct the fusion surface of the lower part of the rear wedge

[0053] Based on the lower longitudinal control lines constructed above, the surface is constructed from front to back in a segmented form of "transition surface + ruled surface + transition surface";

[0054] 3.3) Construct the inner curved surface of the posterior wedge.

[0055] Based on the longitudinal control lines constructed above, construct the surface in the form of a "ruled surface";

[0056] 3.4) Construct the upper curved surface on the outer side of the posterior wedge.

[0057] Based on the longitudinal and lateral control lines constructed above, the surfaces are constructed from top to bottom in a segmented manner of "transition surface + ruled surface + transition surface + ruled surface + transition surface".

[0058] 3.5) Construct the lower outer curved surface of the posterior wedge.

[0059] Based on the longitudinal and lateral control lines constructed above, the surfaces are constructed from top to bottom in a segmented manner of "transition surface + ruled surface + transition surface + ruled surface + transition surface".

[0060] 3.6) Construct the upper blending surface between the fuselage curved surface and the rear wedge.

[0061] Based on the longitudinal control lines, lateral control lines, intersecting lines, transverse control lines, and internal control lines constructed above, a fused surface is constructed in a segmented form of "transition surface + concave surface + transition surface".

[0062] 3.7) Construct the lower blending surface between the fuselage curved surface and the rear wedge.

[0063] Based on the longitudinal control lines, lateral control lines, intersecting lines, transverse control lines, and internal control lines constructed above, a fused surface is constructed in a segmented form of "transition surface + concave surface + transition surface".

[0064] Step 4: Iterative optimization

[0065] Based on the constructed rear wedge surface, parameters can be further adjusted to obtain a high-quality rear wedge surface.

[0066] A method for designing the wedge-shaped rear fuselage of a variable-sweep wing stealth aircraft can be understood as a complex wedge-shaped design approach for multi-component coupling regions, which has the following advantages:

[0067] 1) A wedge-shaped design for the rear fuselage of a variable-tail aircraft is proposed, which is simple and practical.

[0068] 2) The design takes into account all factors, including variable tail fin rotation, component coupling, stealth principles, and aerodynamic drag.

[0069] 3) It can accurately transform design constraints into geometric designs, and effectively transform constraints such as variable tail fin rotation, stealth principles, aerodynamic drag, and component coupling into the design of the wedge shape point position and line tangent control of the rear body to achieve these constraints;

[0070] 4) The design of the rear wedge and the surrounding curved surfaces has been well integrated. While ensuring the requirements for the rotation space of the variable tail fin and the two-dimensional nozzle, the aerodynamic and stealth shape of the rear wedge has been integrated.

[0071] This invention is mainly applied to the design of wedge-shaped tail fins. The method is novel, ingenious, and compact, possessing strong applicability and a wide range of applications, with broad prospects for use in military aircraft design. Attached Figure Description

[0072] Figure 1 A schematic diagram of the overall shape of the posterior wedge.

[0073] Figure 2 A bottom view of the wedge-shaped rear body.

[0074] Figure 3 Side view of the posterior wedge shape

[0075] Figure 4 Rear view of the wedge-shaped body.

[0076] Figure 5 Schematic diagram of the control points and control lines on the upper part of the rear wedge.

[0077] Figure 6 Schematic diagram of the control points and control lines of the lower part of the posterior wedge. Detailed Implementation

[0078] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0079] 1. Determine the boundary of the posterior wedge construction.

[0080] 1.1) Determination of the lateral boundary of the upper front end: In this example, the rotation radius R1 of the variable tail fin is 300mm;

[0081] 1.2) Determination of the lower front transverse boundary: The front transverse boundary is a straight line b1b2;

[0082] 1.3) Determination of the rear lateral boundary and outermost boundary: The short side length of the two-dimensional nozzle is H1, which is 400mm, and the safe distance of the variable tail fin is H2, which is 20mm.

[0083] 1.4) Determination of the outermost upper boundary: The tension α1 of the tangent to curve c3d1 is 0.5;

[0084] 1.5) Determination of the outermost lower boundary: The tension α2 of the tangent line of curve c3d2 is 0.5;

[0085] 1.6) Determination of the upper inner boundary: The tension α3 of the tangent to curve a2n1 is 1;

[0086] 1.7) Determination of the lower inner boundary: The tension α4 of the tangent to curve b2m1 is 1.

[0087] 2. Determine the longitudinal control line of the posterior wedge.

[0088] 2.1) Construct the longitudinal control line of the first cross-section on the upper outer side of the two-dimensional nozzle: the tension α5 of the tangent of curve n1e1 is 1;

[0089] 2.2) Construct the longitudinal control line of the first cross-section on the lower outer side of the two-dimensional nozzle: the tension α6 of the tangent of curve m1e3 is 1;

[0090] 2.3) Based on the upper and lower lateral straight lines within the first section, deduce the actual boundary control lines: the chamfer R2 is 10mm, the lateral tilt angle θ1 is 40°, and the lateral tilt angle θ2 is 40°;

[0091] 2.4) Construct the longitudinal control line of the upper second section behind the variable tail fin rotation ball: the tension α7 of the tangent of curve f1f3 is 1;

[0092] 2.5) Construct the longitudinal control line of the second section below the variable tail fin rotation ball: the tangent tension α8 of curve f4f5 is 1;

[0093] 2.6) Based on the upper and lower lateral straight lines in the second section, deduce the actual boundary control lines: the chamfer R3 is 10mm, the lateral tilt angle θ3 is 40°, and the lateral tilt angle θ4 is 40°;

[0094] 2.7) Construct the internal control line for the transition zone between the upper part of the wedge and the fuselage: the tangent tension α9 of curve g2g3 is 1, and the tangent tension α10 of curve g4f1 is 0.5;

[0095] 2.8) Construct the internal control line for the transition zone between the lower part of the wedge and the fuselage: the tangent tension α11 of curve h2h3 is 1, and the tangent tension α12 of curve h4f4 is 0.5.

[0096] 3. Construct the wedge-shaped surface of the posterior body.

[0097] 3.1) Construct the upper fusion surface of the rear wedge: Based on the upper longitudinal control lines constructed above, construct the surface from front to back in a segmented form of "transition surface + ruled surface + transition surface";

[0098] 3.2) Construct the lower part of the wedge-shaped fusion surface of the rear body: Based on the lower longitudinal control lines constructed above, construct the surface from front to back in a segmented form of "transition surface + ruled surface + transition surface";

[0099] 3.3) Construct the inner curved surface of the wedge: Based on the longitudinal control lines constructed above, construct the curved surface in the form of a "ruled surface";

[0100] 3.4) Construct the upper outer curved surface of the rear wedge: Based on the longitudinal control lines and lateral control lines constructed above, construct the curved surface from top to bottom in a segmented form of "transition surface + ruled surface + transition surface + ruled surface + transition surface";

[0101] 3.5) Construct the lower outer curved surface of the rear wedge: Based on the longitudinal control lines and lateral control lines constructed above, construct the surface from top to bottom in a segmented form of "transition surface + ruled surface + transition surface + ruled surface + transition surface";

[0102] 3.6) Construct the upper blending surface between the fuselage curved surface and the rear wedge: Based on the longitudinal control lines, lateral control lines, intersection lines, transverse control lines, and internal control lines constructed above, construct the blending surface in a segmented form of "transition surface + concave surface + transition surface";

[0103] 3.7) Construct the lower blending surface between the fuselage curved surface and the rear wedge: Based on the longitudinal control lines, lateral control lines, intersection lines, transverse control lines, and internal control lines constructed above, construct the blending surface in a segmented form of "transition surface + concave surface + transition surface". 8. Iterative Optimization

[0104] Based on the constructed rear wedge surface, parameters can be further adjusted to obtain a high-quality rear wedge surface.

[0105] Table 1 Design parameters for the rear body wedge

[0106]

Claims

1. A method for designing the wedge-shaped rear fuselage of a variable-sweep wing stealth aircraft, characterized in that, The steps are as follows: Step 1: Determine the boundary of the posterior wedge construction. 1.1) Determination of the transverse boundary of the upper front end Within the plane A containing the auxiliary shaft of the variable tail and the Z-direction, the rotation radius R1 of the variable tail determines the highest point of the rotating ball in the Z-direction as the upper left limit point a1; within the plane A, the right limit point a2 is selected within the cross-sectional line of the upper part of the fuselage, forming the lateral boundary a1a2 of the upper front end of the rear wedge. 1.2) Determination of the lower front transverse boundary Within plane A, where the auxiliary shaft of the variable tail fin is located and the Z-direction is located, the lowest point of the rotating ball in the Z-direction is determined as the lower left limit point b1; within plane A, the right limit point b2 is selected within the cross-sectional line of the lower part of the fuselage, forming the lateral boundary b1b2 of the lower front end of the rear wedge. 1.3) Determination of the rear lateral boundary and the outermost boundary The short side of the binary nozzle is H1. A straight line K1 parallel to the Y-axis is drawn through the midpoint of the upper and lower vertices of the rear end of the binary nozzle. The right extreme point of the rear transverse boundary is located on the straight line K1. A plane B is drawn through the upper root endpoint n1 of the binary nozzle outlet, the projection of the inner side line of the horizontal tail in the XY plane, and the Z-axis. The intersection of plane B and K1 forms the right extreme point c1 of the rear transverse boundary. Based on the parallel principle of the two-dimensional nozzle and the variable tail fin, the variable tail fin rotates outward and translates the variable tail fin safety distance H2, intersecting the plane A with the line P. Take the point c2 where the maximum value in the Y direction is located, and draw the line of symmetry with the inner side line of the horizontal tail through point c2, the plane C containing the Z axis and the boundary line K2. Draw plane D, which is formed by the projection of the nozzle boundary onto the XY plane and the Z-axis. Draw plane E, which is parallel to plane D, through point n1. Plane E intersects the boundary line K2 at point c3, which is the left extreme point of the rear transverse boundary, forming the rear transverse boundary c1c3 and the outermost boundary c2c3. 1.4) Determination of the outermost upper boundary Through point c3, construct a plane F parallel to the ZX plane. Plane F intersects the upper curved surface of the rear fuselage at point d1. Construct a spline curve c3d1 through points c3 and d1. At point d1, the tangent tension of the curve is α1, forming the outermost upper boundary c3d1. 1.5) Determination of the outermost lower boundary Plane F intersects the lower curved surface of the rear fuselage at point d2. A spline curve c3d2 is drawn through points c3 and d2. At point d2, the tangent tension of the curve is α2, forming the outermost upper boundary c3d2. 1.6) Determination of the upper inner boundary Draw a spline curve a2n1 through points a2 and n1. The tangent tension α3 of the curve at point a2 forms the upper inner boundary a2n1. Draw a straight line through points c1 and n1 to form the inner boundary c1n1. 1.7) Determination of the lower inner boundary Draw a spline curve b2m1 through point b2 and the lower root endpoint m1 of the binary nozzle outlet. The tangent tension α4 of the curve at point b2 forms the lower inner boundary b2m1. Draw a straight line through points c1 and m1 to form the inner boundary c1m1. Step 2: Determine the longitudinal control line of the posterior wedge. 2.1) Construct the longitudinal control line of the first cross-section on the upper outer side of the two-dimensional nozzle. Through point n1, draw plane G formed by the nozzle trailing edge line and the Z-axis. Plane G intersects c3d1 at point e1. Through points n1 and e1, draw spline curve n1e1. The spline curve is tangent to the upper trailing edge line of the nozzle. At point n1, the tangent tension of the curve is α5. Plane G intersects c2c3 at point e2. Connect e1 and e2 to form the upper lateral straight line e1e2. 2.2) Construct the longitudinal control line of the first cross-section on the lower outer side of the two-dimensional nozzle. Through point m1, draw plane H formed by the nozzle trailing edge line and the Z-axis. Plane H intersects c3d2 at point e3. Through points m1 and e3, draw spline curve m1e3. The spline curve is tangent to the lower trailing edge line of the nozzle. At point m1, the tangent tension of the curve is α6. Connect e2 and e3 to form the lower lateral straight line e2e3. 2.3) Derive the actual boundary control lines based on the upper and lower lateral straight lines within the first section. Chamfer R2 between the upper lateral line e1e2 and the lower lateral line e2e3. Take the midpoint e4 of the chamfer. Translate the upper lateral line e1e2, the lower lateral line e2e3, and the chamfer R2 from point e4 to point e2, keeping the position of edge c2c3 unchanged. Due to the change in position, the upper lateral line e1e2 evolves into line E1. Draw spline E2 through point e1, which transitions with line E1 by an arc. Draw plane I parallel to XY through e2. The angle between the upper lateral line E1 and its projection line in plane I is the lateral tilt angle θ1. The lower lateral line e2e3 changes position and becomes line E3. A spline E4 is drawn through point e3, which transitions with line E3 by an arc. The angle between the lower lateral line E3 and its projection line in plane I is the lateral tilt angle θ2. The chamfer R2 changes position and becomes chamfer E5. The actual lateral boundary control line is E6, which includes E1+E2+E3+E4+E5. 2.4) Construct the longitudinal control line of the upper second section behind the variable tail fin rotation ball. The trailing edge of the intersection point between the variable tail fin spherical ball and the tail fin is connected to a plane J parallel to the YZ plane. Plane J intersects the straight line c3d1 and the spline c2c3 at points f1 and f2 respectively. Connecting points f1 and f2 forms the upper lateral straight line f1f2. Plane J intersects the spline a2n1 at point f3. Through points f1 and f3, draw the spline curve f1f3. At point f3, the tangent tension of the curve is α7. 2.5) Construct the longitudinal control line of the lower second section behind the variable tail fin rotation ball. From the trailing edge point of the intersection of the variable tail fin spherical ball and the tail fin, there is a plane K parallel to the YZ plane. The plane K intersects the spline c3d2 at point f4. Connect points f2 and f4 to form the lower lateral straight line f2f4. The plane K intersects b2m1 at point f5. Through points f4 and f5, draw the spline curve f4f5. At point f5, the tangent tension of the curve is α8. 2.6) Derive the actual boundary control lines based on the upper and lower lateral straight lines within the second section. Chamfer R3 between the upper lateral lines f1f2 and f2f3. Take the midpoint f6 of the chamfer. Translate the upper lateral lines f1f2, f2f3, and R3 from point f6 to point f2, keeping the position of edge c2c3 unchanged. Due to the change in position, the upper lateral lines f1f2 evolve into line F1. Draw spline F2 through point f1, which transitions with line F1 by an arc. Draw a plane L parallel to XY through f2. The angle between the upper lateral lines F1 and their projection line in plane L is the lateral tilt angle θ3. The lower lateral line f2f3 evolves into line F3 due to a change in position. A spline F4 is drawn through point f4, which transitions with line F3 by an arc. The angle between the lower lateral line F3 and its projection line in plane L is the lateral tilt angle θ4. The chamfer R3 evolves into chamfer F5 due to a change in position. The actual lateral boundary control line is F6, which includes F1+F2+F3+F4+F5. 2.7) Construct the internal control line between the upper part of the wedge and the transition area of ​​the fuselage. Take the midpoint g1 of line E1 and the midpoint g2 of line F1. Draw the line g1g2. Draw a plane M parallel to the plane XY through point g2. The plane M intersects the line P at point g3. Draw the spline curve g2g3 through points g2 and g3. At point g2, the tangent tension of the curve is α9. The intersecting line P intersects the upper transverse boundary a1a2 at point g4. Through points g4 and f1, construct the spline curve g4f1. At point f1, the tangent tension of the curve is α10. 2.8) Construct the internal control line between the lower part of the wedge and the transition area of ​​the fuselage. Take the midpoint h1 of line F1 and the midpoint h2 of line F2. Draw the line h1h2. Draw a plane N parallel to the plane XY through point h2. Plane N intersects the line P at point h3. Draw the spline curve h2h3 through points h2 and h3. At point h2, the tangent tension of the curve is α11. The line P intersects the lower horizontal boundary b1b2 at point h4. Draw the spline curve h4f4 through points h4 and f4. At point f4, the tangent tension of the curve is α12. Step 3: Construct the wedge-shaped surface of the posterior body 3.1) Construct the fusion surface of the upper part of the rear wedge Based on the upper longitudinal control lines constructed above, the surface is constructed from front to back in a segmented form of "transition surface + ruled surface + transition surface"; 3.2) Construct the fusion surface of the lower part of the rear wedge Based on the lower longitudinal control lines constructed above, the surface is constructed from front to back in a segmented form of "transition surface + ruled surface + transition surface"; 3.3) Construct the inner curved surface of the posterior wedge. Based on the longitudinal control lines constructed above, construct the surface in the form of a "ruled surface"; 3.4) Construct the upper curved surface on the outer side of the posterior wedge. Based on the longitudinal and lateral control lines constructed above, the surfaces are constructed from top to bottom in a segmented manner of "transition surface + ruled surface + transition surface + ruled surface + transition surface". 3.5) Construct the lower outer curved surface of the posterior wedge. Based on the longitudinal and lateral control lines constructed above, the surfaces are constructed from top to bottom in a segmented manner of "transition surface + ruled surface + transition surface + ruled surface + transition surface". 3.6) Construct the upper blending surface between the fuselage curved surface and the rear wedge. Based on the longitudinal control lines, lateral control lines, intersecting lines, transverse control lines, and internal control lines constructed above, a fused surface is constructed in a segmented form of "transition surface + concave surface + transition surface". 3.7) Construct the lower blending surface between the fuselage curved surface and the rear wedge. Based on the longitudinal control lines, lateral control lines, intersecting lines, transverse control lines, and internal control lines constructed above, a fused surface is constructed in a segmented form of "transition surface + concave surface + transition surface". Step 4: Iterative optimization Based on the constructed rear wedge surface, parameters can be further adjusted to obtain a high-quality rear wedge surface.

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