Tail-seat amphibious aircraft with sliding and foldable wings and design method

Abstract

The present invention provides a tail - seat type amphibious aircraft with a sliding and foldable wing and a design method, which relates to the technical field of amphibious aircraft. By designing a slidable and foldable wing structure, the present invention meets the different requirements for the center of gravity, aerodynamic center and metacenter in two modes of in - air cruise and water - surface perch of the tail - seat type water - air amphibious multimodal aircraft, enabling the aircraft to always maintain the tail - seat state when perching on the water surface, meeting the needs of performing water - surface operation tasks, and being able to take off quickly under high - sea - state conditions. It avoids the difficulties in designing the relative positions among the center of gravity, aerodynamic center and metacenter of the traditional tail - seat type fixed - wing aircraft in two states of water - surface floating and in - air cruise flight, and the problem that the traditional layout design is difficult to ensure the stability of the aircraft when floating on the water surface.

Description

Technical Field

[0001] The present invention relates to the technical field of amphibious aircraft, and specifically to a tail-sitter amphibious aircraft with sliding and foldable wings and a design method thereof. Background Art

[0002] Water-air amphibious multimodal unmanned aircraft have capabilities such as air-sea three-dimensional patrol, search, environmental monitoring, transportation, etc., and have received extensive attention in recent years. Existing water-air amphibious aircraft at home and abroad are mostly vertical take-off and landing rotorcraft. For example, the Chinese patent application "Water-air amphibious glider capable of vertical take-off and landing flight" with the publication number CN106516110A and the Chinese patent application "Large amphibious logistics drone capable of vertical take-off and landing" with the publication number CN114802726A. Although such aircraft have relatively high floating stability on the water surface, the cruise efficiency of rotorcraft in the air is low, and the range and endurance are short, making it difficult to meet the mission requirements of vast waters.

[0003] In contrast, tail-sitter fixed-wing water-air amphibious multimodal aircraft not only have high cruise efficiency but also have the ability of vertical take-off and landing, and can meet the flight requirements of long endurance and long range. For example, the Chinese patent application "Tail-sitter sea-air cross-domain aircraft device based on a quadrotor drive mode" with the publication number CN110775262A. Summary of the Invention

[0004] Technical Problems to be Solved

[0005] During the design and verification of a tail-sitter fixed-wing water-air amphibious multimodal aircraft, in order to increase the range and endurance, the aircraft is required to have a large lift-to-drag ratio during the cruise phase. Therefore, a large aspect ratio design needs to be adopted. For an aircraft with a large aspect ratio design, in order to meet the requirements of flight static stability, the center of gravity of the aircraft during the cruise phase is located in front of the aerodynamic focus. When the aircraft perches on the water surface in a tail-sitter form, since the pontoons providing buoyancy are located at the outer ends of the wings and the outer ends of the tail wings, close to the rear of the fuselage, at this time, the center of gravity of the aircraft is relatively high from the water surface, and the longitudinal stability performance of the aircraft on the water surface is low, and it is extremely vulnerable to sea conditions and prone to capsizing, making it difficult to meet the needs of performing water surface operation tasks, such as being a water surface relay node, etc. Moreover, when the aircraft capsizes on the water surface, if the aircraft needs to take off again on the water surface, it is necessary to adjust the aircraft attitude through differential power to achieve water surface take-off, as described in the solution recorded in the literature CN110775262A. However, for an aircraft with only tail power of the fuselage, it is difficult to achieve water surface re-take-off once it capsizes.

[0006] In view of the above problems, the present invention proposes a tail-sitter amphibious aircraft with a sliding and foldable wing and a design method. By designing a slidable and foldable wing structure, the different requirements for the center of gravity, aerodynamic center, and metacenter in the two modes of in-air cruise and water-surface parking of the tail-sitter water-air amphibious multimodal aircraft are met. When the aircraft is parked on the water surface, it can always maintain the tail-sitter state, meet the needs of performing water-surface operation tasks, and can also take off quickly under high sea conditions. It avoids the difficulties in designing the relative positions of the center of gravity, aerodynamic center, and metacenter of the traditional tail-sitter fixed-wing aircraft in the two states of water-surface floating and in-air cruise flight, and the problem that the traditional layout design is difficult to ensure the stability of the aircraft when floating on the water surface.

[0007] The technical solution of the present invention is as follows:

[0008] A tail-sitter amphibious aircraft with a sliding and foldable wing, including a fuselage, a canard located at the front of the fuselage, a foldable wing, and a vertical tail fixedly connected to the middle of the wing;

[0009] A moving pair is formed between the foldable wing and the fuselage, and the foldable wing can move back and forth along the fuselage axis under power drive and be locked in place;

[0010] The foldable wing is divided into two parts on the left and right sides of the fuselage. The single-side wing is divided into an inner wing section and an outer wing section. A rotating pair is formed between the inner wing section and the outer wing section of the same-side wing. The outer wing section can rotate relative to the inner wing section around the rotation axis under power drive and be locked in place. The rotation axis is parallel to the fuselage axis;

[0011] Floats are fixed at the tip position of the vertical tail and the tip positions of the outer wing sections on both sides of the foldable wing;

[0012] When the aircraft is in the in-air cruise mode, the foldable wing moves along the fuselage axis to the rear limit position and is in the locked state, and the inner wing section and the outer wing section of the same-side wing are flush and locked;

[0013] When the aircraft is in the water-surface parking mode, the foldable wing moves along the fuselage axis to the front limit position and is in the locked state, and the outer wing section of the same-side wing rotates around the rotation axis in the direction away from the vertical tail to the in-place position and is locked, so that the fuselage is within the triangle formed by the three floats.

[0014] Further, the cross-section of the fuselage is rectangular, a chute extending along the axis of the fuselage is formed on the upper surface of the fuselage, a slider capable of being embedded in the chute is provided on the inner surface of the middle part of the foldable wing, and a linear motor is installed inside the fuselage. Through the cooperation of the chute and the slider, the linear motor drives the slider to move along the chute, so as to realize the forward and backward movement of the foldable wing along the axis of the fuselage; and electric latches are arranged at the front and rear limit positions of the chute. When the slider is at the front and rear limit positions of the chute, the electric latches can be controlled to lock or unlock the slider.

[0015] Further, the outer end surface of the inner wing segment and the inner end surface of the outer wing segment are connected by a limit hinge, and the outer wing segment is driven to rotate around the hinge rotation axis by a servo motor; the outer end surface of the inner wing segment and the inner end surface of the outer wing segment are also matched through a telescopic pin and a pin hole. When the inner wing segment and the outer wing segment are in a flush state, the telescopic pin on the outer end surface of the inner wing segment can be controlled to insert into the pin hole on the inner end surface of the outer wing segment to lock the outer wing segment, or be controlled to pull out from the pin hole to unlock the outer wing segment; when the outer wing segment rotates around the hinge rotation axis to the folding limit position, the rotation angle of the outer wing segment is maintained by the limit hinge.

[0016] Further, the pontoon is of a rotary body structure, and the axis of the pontoon is parallel to the axis of the fuselage.

[0017] Further, when the aircraft is in the water parking mode, the projection points of the axes of the three pontoons on the cross-section of the fuselage form a right triangle or an acute triangle, and the projection point of the axis of the fuselage on the cross-section of the fuselage is located at the circumcenter position of the right triangle or the acute triangle.

[0018] The present invention also provides a design method for the above-mentioned aircraft, including the following steps:

[0019] Step 1: Optimized design of the flight performance of the aircraft in the cruise state:

[0020] Step 1.1: Establish a basic configuration of the aircraft with a fuselage, canards, straight wings and a vertical tail, and select the canard span 、the chord length distribution of the canards 、the wing span 、the chord length distribution of the wings and the airfoil section shape of the wings as design parameters;

[0021] The canard span refers to the length from the central axis of the fuselage to the tip of the canard; the chord length distribution of the canards refers to the length from the leading edge to the trailing edge of the canards at different positions in the canard span direction; the wing span refers to the length from the central axis of the fuselage to the tip of the outer wing segment; the chord length distribution of the wings refers to the length from the leading edge to the trailing edge of the wings at different positions in the wing span direction; the airfoil section shape of the wings refers to the airfoil section shape of the wings at a set position in the wing span direction;

[0022] Step 1.2: With the maximum lift-drag ratio of the aircraft as the design goal, under the first constraint of the center of gravity position, lift constraint, pitching moment constraint, and wing structure thickness constraint, based on the basic configuration of the aircraft, optimize the design parameters selected in Step 1.1 based on flight performance to obtain an intermediate design result;

[0023] The first constraint of the center of gravity position means that the ratio of the distance between the center of gravity and the aerodynamic center of the aircraft to the mean aerodynamic chord of the wing is within a set range; the lift constraint means that the lift generated by the aircraft at the design cruise speed, design cruise altitude, and design cruise angle of attack is equal to the gravity of the aircraft; the pitching moment constraint means that the pitching moment of the aircraft at the design cruise speed, design cruise altitude, and design cruise angle of attack is less than a set value to ensure that the aircraft can fly in steady cruise; the wing structure thickness constraint means that the wing thickness can meet the spatial requirements for the internal structure layout of the wing;

[0024] Step 2: Optimization design of the water surface stability of the floating state of the aircraft:

[0025] Step 2.1: Select the moving distance of the wing along the fuselage axis , the distance between the rotation axis in the single-side wing and the fuselage axis and the rotation angle of the outer wing section in the single-side wing as design parameters;

[0026] Step 2.2: Based on the intermediate design result obtained in Step 1, establish a folding configuration. With the optimal stability in all directions of the folding configuration as the design goal, under the second constraint of the center of gravity position, moment of inertia constraint, and wing structure constraint, optimize the design parameters selected in Step 2.1 to obtain the final optimized design result;

[0027] The second constraint of the center of gravity position means that in the folding configuration, when the aircraft is in the tail-sitting attitude, the center of gravity is below the metacenter of the aircraft, and the distance between the metacenter and the center of gravity is not less than a set value; the moment of inertia constraint means that in the folding configuration, when the aircraft is in the tail-sitting attitude, the restoring moment changes continuously with the change of the floating tilt angle without sudden change of the restoring moment; the wing structure constraint means that the position of the rotation axis of the outer wing section does not affect the operation of the internal structure of the wing;

[0028] Step 3: Determine whether the final optimized design result obtained in Step 2 meets the requirements of stability in all directions in the folding configuration. If not, return to Step 1 to re-establish the basic configuration.

[0029] Beneficial effects:

[0030] The tail - sitter amphibious aircraft with a sliding and foldable wing proposed by the present invention, by designing a slidable and foldable wing structure, meets the different requirements for the center of gravity, aerodynamic focus, and metacenter in the two modes of in - air cruise and water - surface parking of the tail - sitter water - air amphibious multimodal aircraft. When the aircraft parks on the water surface, it can always maintain the tail - sitter state, meet the needs of performing water - surface operation tasks, and can also take off quickly under high - sea - state conditions, enabling the aircraft to have both high flight performance in the in - air cruise state and high stability in the water - surface parking state.

[0031] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present invention. Brief Description of the Drawings

[0032] The above - mentioned and / or additional aspects and advantages of the present invention will become apparent and be easily understood from the description of the embodiments in conjunction with the following drawings, where:

[0033] Figure 1 is a three - dimensional schematic diagram of the water - air amphibious aircraft in the in - air cruise mode;

[0034] Figure 2 is a front view of the water - air amphibious aircraft in the in - air cruise mode;

[0035] Figure 3 is a side view of the water - air amphibious aircraft in the in - air cruise mode;

[0036] Figure 4 is a top view of the water - air amphibious aircraft in the in - air cruise mode;

[0037] Figure 5 is a three - dimensional schematic diagram of the water - air amphibious aircraft in the water - surface parking mode;

[0038] Figure 6 is a front view of the water - air amphibious aircraft in the water - surface parking mode;

[0039] Figure 7 is a side view of the water - air amphibious aircraft in the water - surface parking mode;

[0040] Figure 8 is a top view of the water - air amphibious aircraft in the water - surface parking mode;

[0041] Figure 9 is an optimization design block diagram of the tail - sitter amphibious aircraft with a sliding and foldable wing.

[0042] In the figures: 1, fuselage; 2, canard; 3, inner - segment wing; 4, outer - segment wing; 5, vertical tail; 6, float. Detailed Embodiments

[0043] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0044] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0045] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0046] In this embodiment, a tail-seat type amphibious aircraft with a sliding and foldable wing is proposed, and a design method for the aircraft is given. The aircraft can take off vertically by means of land takeoff, shipboard takeoff, etc., or can be air-dropped by a carrier aircraft and stay for a long time in the target mission waters at a long distance; when receiving a mission command, it vertically lands on the target waters and perches on the water surface to perform surface missions, such as serving as a surface relay node, collecting water environment information, etc.; after the surface mission is completed, the aircraft vertically takes off again from the water surface in a tail-seat manner and returns. In this scenario, in the air cruise mode of flying to the target mission waters at a long distance and staying for a long time, the aircraft is required to have a high lift-to-drag ratio and a large aspect ratio; while in the surface perching mode of performing surface missions, the aircraft is required to have stable stability performance in all directions under high sea state conditions, maintain the tail-seat state, meet the needs of performing surface missions, and be able to take off stably on the water surface. For this reason, in the air cruise mode, the tail-seat type vertical takeoff and landing amphibious aircraft with foldable wings proposed in this embodiment has the wings fully extended and slid along the fuselage to the rear limit position. The wingspan is relatively long, with a suitable sweep angle, aspect ratio, and tip-to-root ratio, enabling the aircraft to have better cruise flight performance; while in the surface perching mode, the wings are folded and slid along the fuselage to the front limit position. The buoyancy of the aircraft is mainly provided by the floats at both ends of the wings and the floats at the outer ends of the vertical tail. In this mode, since the floats are always on the water surface, and the wings with floats and the vertical tail slide along the fuselage to the front limit position, the main body structure of the aircraft is located behind the wings. Therefore, the center of gravity of the aircraft is lower than the center of buoyancy at this time, thus ensuring that the aircraft has static stability at a small angle; and the triangle formed by the floats at both ends of the folded wings and the floats at the outer ends of the vertical tail wraps the fuselage, thus enabling the aircraft to have a high distance between the center of gravity and the center of stability and stable stability performance in all directions.

[0047] As Figure 1 shown, the aircraft includes a fuselage, a canard located at the front of the fuselage, a foldable wing, and a vertical tail fixedly connected to the middle of the wing. The power system of the aircraft is not shown in the figure. The power system can adopt a tractor propeller at the head of the fuselage or tractor propellers installed on the inner wing segments of the foldable wings on both sides. In addition, a control system and mission payloads are arranged inside the fuselage, and the specific installation positions are determined according to design requirements.

[0048] A prismatic pair is formed between the foldable wing and the fuselage. The foldable wing can move back and forth along the fuselage axis under power drive and be locked in place. There are various ways to implement this prismatic pair. In this embodiment, the cross-section of the fuselage is rectangular, and a chute extending along the fuselage axis is formed on the upper surface of the fuselage. A slider capable of being embedded in the chute is provided on the inner surface of the middle part of the foldable wing. A linear motor is installed inside the fuselage. Through the cooperation of the chute and the slider, the linear motor drives the slider to move along the chute, realizing the back-and-forth movement of the foldable wing along the fuselage axis. Electric latches are arranged at the front and rear limit positions of the chute. When the slider is at the front and rear limit positions of the chute, the electric latches can be controlled to lock or unlock the slider.

[0049] The foldable wing is divided into two parts on the left and right sides of the fuselage. Each single-side wing is divided into an inner wing segment and an outer wing segment. A revolute pair is formed between the inner wing segment and the outer wing segment of the same-side wing. The outer wing segment can rotate relative to the inner wing segment around the rotation axis under power drive and be locked in place. The rotation axis is parallel to the fuselage axis. In this embodiment, the outer end face of the inner wing segment and the inner end face of the outer wing segment are connected by a limit hinge, and a servo motor drives the outer wing segment to rotate around the hinge rotation axis. The outer end face of the inner wing segment and the inner end face of the outer wing segment are also matched through a telescopic pin and a pin hole. When the inner wing segment and the outer wing segment are in a flush state, the telescopic pin on the outer end face of the inner wing segment can be controlled to insert into the pin hole on the inner end face of the outer wing segment to lock the outer wing segment, or be controlled to pull out from the pin hole to unlock the outer wing segment. When the outer wing segment rotates around the hinge rotation axis to the folding limit position, the rotation angle of the outer wing segment is maintained by the limit hinge. In addition, control surfaces are arranged at the trailing edge of the wing to realize the roll and pitch control of the aircraft.

[0050] A vertical tail is fixedly connected to the outer surface of the middle part of the foldable wing. The vertical tail can move synchronously with the foldable wing along the fuselage axis. Control surfaces are arranged at the trailing edge of the vertical tail to realize the yaw control of the aircraft.

[0051] Floats are fixed at the tip position of the vertical tail and the tip positions of the outer wing segments on both sides of the foldable wing, which are used to provide buoyancy for the aircraft in the water landing mode. In this embodiment, the float is of a rotary body structure, the float axis is parallel to the fuselage axis, and the shape of the float is designed with low drag characteristics to reduce the drag of the aircraft during air cruise.

[0052] As Figures 1 to 4 shown, when the aircraft is in the air cruise mode, the foldable wing moves along the fuselage axis to the rear limit position of the fuselage and is in the locked state, and the inner wing segment and the outer wing segment of the same-side wing are flush and locked, forming an external configuration that meets the air cruise mode.

[0053] As Figures 5 to 8As shown, when the aircraft is in the water landing mode, the foldable wings move along the fuselage axis to the front limit position of the fuselage and are in the locked state, and the outer wing segments of the wings on the same side rotate around the rotation axis to the position away from the vertical tail and are locked, so that the fuselage is within the triangle formed by three pontoons. Specifically, the projection point of the fuselage axis on the cross-section of the fuselage is within the triangle formed by the projection points of the axes of the three pontoons on the cross-section of the fuselage. And to meet the requirements of water stability in all directions, this triangle should be a right triangle or an acute triangle.

[0054] The pontoons at the wing tip positions of the outer wing segments of the wings and the pontoons at the wing tip positions of the vertical tail form the external configuration required for the water landing mode of the aircraft.

[0055] In this embodiment, a design method for the aircraft is also given. Since the aircraft mainly has the external configuration in the air cruise mode and the external configuration in the water landing mode, during design, it is mainly divided into the optimization design process of the flight performance in the cruise state and the optimization design process of the water stability in the floating state. Specifically, it includes the following steps:

[0056] Step 1: Optimization design of the flight performance of the aircraft in the cruise state:

[0057] Step 1.1: Establish a basic configuration of the aircraft with a fuselage, canards, straight wings and a vertical tail, and select the canard span 、the chord length distribution of the canards 、the wing span 、the chord length distribution of the wings and the airfoil section shape of the wings as design parameters;

[0058] The canard span refers to the length from the central axis of the fuselage to the wing tip of the canard; the chord length distribution of the canards refers to the length from the leading edge to the trailing edge of the canards at different positions in the canard span direction; the wing span refers to the length from the central axis of the fuselage to the wing tip of the outer wing segment; the chord length distribution of the wings refers to the length from the leading edge to the trailing edge of the wings at different positions in the wing span direction; the airfoil section shape of the wings refers to the airfoil section shape of the wings at a set position in the wing span direction.

[0059] Step 1.2: With the maximum lift-to-drag ratio of the aircraft as the design goal, under the first constraint of the center of gravity position, lift constraint, pitching moment constraint and wing structure thickness constraint, based on the basic configuration of the aircraft, perform optimization design of the design parameters selected in Step 1.1 based on flight performance to obtain an intermediate design result;

[0060] The first constraint on the center of gravity position means that the ratio of the distance between the center of gravity and the aerodynamic center of the aircraft to the mean chord length of the wing is within a set range; the lift constraint means that the lift generated by the aircraft at the designed cruise speed, designed cruise altitude, and designed cruise angle of attack is equal to the gravity of the aircraft; the pitching moment constraint means that the pitching moment of the aircraft at the designed cruise speed, designed cruise altitude, and designed cruise angle of attack is less than a set small value to ensure that the aircraft can fly in a steady cruise; the wing structure thickness constraint means that the wing thickness can meet the spatial requirements for the internal structure layout of the wing.

[0061] Step 2: Optimization design of the water surface stability of the floating state of the aircraft:

[0062] Step 2.1: Select the moving distance of the wing along the fuselage axis , the distance between the rotation axis in the single-sided wing and the fuselage axis and the rotation angle of the outer wing section in the single-sided wing as design parameters;

[0063] Step 2.2: Based on the intermediate design result obtained in Step 1, establish a folding configuration. With the optimal stability in all directions of the folding configuration as the design goal, under the second constraint on the center of gravity position, the moment of inertia constraint, and the wing structure constraint, optimize the design parameters selected in Step 2.1 to obtain the final optimized design result;

[0064] The second constraint on the center of gravity position means that in the folding configuration, when the aircraft is in the tailstock attitude, the center of gravity is below the metacenter of the aircraft, and the distance between the metacenter and the center of gravity is not less than a set value; the moment of inertia constraint means that in the folding configuration, when the aircraft is in the tailstock attitude, the restoring moment changes continuously with the change of the floating tilt angle without sudden change of the restoring moment; the wing structure constraint means that the position of the rotation axis of the outer wing section does not affect the operation of the internal structure of the wing.

[0065] Step 3: Determine whether the final optimized design result obtained in Step 2 meets the requirements of stability in all directions in the folding configuration. If not, return to Step 1 to re-establish the basic configuration.

[0066] Through the above two-step optimization design process, it is ensured that the aircraft has both excellent air cruise performance and excellent water surface parking and floating state stability performance. In this embodiment, through the optimization design of the water surface stability of the floating state, it is determined that in the folded state, the distance from the projection point of the fuselage axis on the cross-section of the fuselage to the projection points of the axes of the three pontoons on the cross-section of the fuselage is equal, that is, it is at the circumcenter position of the triangle formed by the projection points of the axes of the three pontoons on the cross-section of the fuselage.

[0067] The tail-seat type amphibious aircraft with a sliding and foldable wing proposed in this embodiment, by designing a slidable and foldable wing structure, meets the different requirements for the center of gravity, aerodynamic center and metacenter in the two modes of in-air cruising and water-surface perching of the tail-seat type water-air amphibious multimodal aircraft. When the aircraft perches on the water surface, it can always maintain the tail-seat state, meet the needs of performing water-surface operation tasks, and can also take off quickly under high sea state conditions, realizing that the aircraft has both high flight performance in the in-air cruising state and high stability in the water-surface perching state.

[0068] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A tail-seat amphibious aircraft with sliding foldable wings, comprising a fuselage, a canard located at the front of the fuselage, a foldable wing, and a vertical tail fixed to the middle of the wing; characterized in that: A moving pair is formed between the foldable wing and the fuselage, and the foldable wing can be moved forward and backward along the axis of the fuselage under power drive and locked in place; The foldable wing is divided into two parts located on the left and right sides of the fuselage, and the wing on one side is divided into an inner wing section and an outer wing section. A revolute pair is formed between the inner wing section and the outer wing section of the wing on the same side, and the outer wing section can rotate relative to the inner wing section around a revolute axis under power drive and be locked in place, and the revolute axis is parallel to the fuselage axis; Floats are fixed at the wing tip of the vertical tail and the wing tips of the outer wing sections on both sides of the foldable wing; When the aircraft is in an air cruise mode, the foldable wing moves along the fuselage axis to the rear limit position and is in a locked state, and the inner wing section and the outer wing section of the wing on the same side are flush and locked, the wing is fully unfolded, the wing span is relatively long, and has the required sweep angle, aspect ratio and tip-to-root ratio, forming an external configuration that meets the air cruise mode; When the aircraft is in the water surface perching mode, the aircraft is in a tail seat state; the foldable wings move along the fuselage axis to the front limit and are in a locked state, the buoyancy of the aircraft is provided by the pontoons at both ends of the wings and the pontoons at the outer ends of the vertical tail, the pontoons are always on the water surface, and the center of gravity of the aircraft is lower than the center of buoyancy; and the outer wing section of the wing on the same side rotates around the rotation axis in the direction away from the vertical tail and is locked in place, the projection point of the fuselage axis on the fuselage cross section is in the triangle formed by the projection points of the three pontoon axes on the fuselage cross section, and the triangle is a right triangle or an acute triangle, so that the aircraft has isotropic stability performance.

2. A tail-seat amphibious aircraft with sliding foldable wings according to claim 1, characterized in that: The fuselage cross-section is rectangular, and a slide groove is opened on the upper surface of the fuselage along the axis direction of the fuselage. The inner surface of the middle part of the foldable wing has a slider that can be embedded in the slide groove, and a linear motor is installed inside the fuselage. Through the cooperation of the slide groove and the slider, the linear motor drives the slider to move along the slide groove, so as to realize the forward and backward movement of the foldable wing along the axis of the fuselage; and electric locks are arranged at the front and rear limit positions of the slide groove. When the slider is at the front and rear limit positions of the slide groove, the electric lock can be controlled to lock or unlock the slider.

3. The tail-seat amphibious aircraft with sliding foldable wings according to claim 1, characterized in that: The outer end surface of the inner wing section is connected to the inner end surface of the outer wing section by a limit hinge, and the outer wing section is driven to rotate around the hinge rotation axis by the servo; when the outer wing section rotates around the hinge rotation axis to the folding limit position, the rotation angle of the outer wing section is maintained by the limit hinge.

4. A tail-seat amphibious aircraft with sliding foldable wings according to claim 3, characterized in that: The outer end surface of the inner wing section and the inner end surface of the outer wing section are also matched through telescopic pins and pin holes. When the inner wing section and the outer wing section are in a flush state, the telescopic pin on the outer end surface of the inner wing section can be controlled to be inserted into the pin hole on the inner end surface of the outer wing section to lock the outer wing section, or controlled to be pulled out from the pin hole to unlock the outer wing section.

5. The tail-seat amphibious aircraft with sliding foldable wings according to claim 1, characterized in that: The buoy is a rotating body structure, and the buoy axis is parallel to the fuselage axis.

6. The tail-seat amphibious aircraft with sliding foldable wings according to claim 1, characterized in that: When the aircraft is in the water surface parking mode, the projection points of the three pontoon axes on the fuselage cross section form a right triangle or an acute triangle, and the projection points of the fuselage axes on the fuselage cross section are located at the circumcenter position of the right triangle or the acute triangle.

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