阅读说明：本技术 可垂直起降的固定翼飞机及其控制方法 (Fixed-wing aircraft capable of taking off and landing vertically and control method thereof ) 是由 王林 于 2021-10-29 设计创作，主要内容包括：本发明公开了一种可垂直起降的固定翼飞机及其控制方法,所述固定翼飞机包括固定连接在机身上的前机翼和后机翼,还包括前动力装置和后动力装置,前动力装置以固定角度安装在前机翼上,后动力装置以固定角度安装在后机翼上,所述前机翼和后机翼的安装角均为20-60度,前动力装置和后动力装置的轴线与机身纵轴线之间的夹角均为20-60度。本发明在前后机翼上分别设置前后动力装置,且前后动力装置均以固定角度安装在前后机翼上,不设置轴线可倾转的动力装置,大大降低了飞机动力系统的复杂性和故障率,提高了可靠性和安全性。本发明可实现垂直起降,具有巡航效率高、航程远、载荷大、制造简单、成本低等绝对优势。(The invention discloses a fixed wing aircraft capable of vertically taking off and landing and a control method thereof, wherein the fixed wing aircraft comprises a front wing and a rear wing which are fixedly connected to an aircraft body, and further comprises a front power device and a rear power device, the front power device is arranged on the front wing at a fixed angle, the rear power device is arranged on the rear wing at a fixed angle, the installation angles of the front wing and the rear wing are both 20-60 degrees, and the included angles between the axial lines of the front power device and the rear power device and the longitudinal axis of the aircraft body are both 20-60 degrees. The front power device and the rear power device are respectively arranged on the front wing and the rear wing, are both arranged on the front wing and the rear wing at a fixed angle, and are not provided with power devices with axes capable of tilting, so that the complexity and the failure rate of an aircraft power system are greatly reduced, and the reliability and the safety are improved. The invention can realize vertical take-off and landing and has the absolute advantages of high cruising efficiency, long voyage, large load, simple manufacture, low cost and the like.)

1. A fixed wing aircraft capable of vertically taking off and landing comprises a front wing and a rear wing which are fixedly connected to an aircraft body, and is characterized by further comprising a front power device and a rear power device, wherein the front power device is installed on the front wing at a fixed angle, the rear power device is installed on the rear wing at a fixed angle, the installation angles of the front wing and the rear wing are both 20-60 degrees, and the included angles between the axial lines of the front power device and the rear power device and the longitudinal axis of the aircraft body are both 20-60 degrees.

2. The fixed wing aircraft as claimed in claim 1, wherein the front wing is fixedly connected to the left and right sides of the front portion of the fuselage, the rear wing is fixedly connected to the left and right sides of the rear portion of the fuselage, the fuselage cavity located in front of the front wing forms a nose cabin, the fuselage cavity located between the front wing and the rear wing forms a belly cabin, and the fuselage cavity located behind the rear wing forms a tail cabin.

3. The fixed-wing aircraft of claim 2, wherein the length of the aft bay is less than the length of the nose bay.

4. The fixed wing aircraft as claimed in claim 1, wherein the front wing is fixedly connected to the front end of the fuselage and extends to the left and right sides, the rear wing is fixedly connected to the rear end of the fuselage and extends to the left and right sides, and the front wing, the rear wing and the fuselage are connected in an i-shape.

5. The fixed wing aircraft of claim 1, wherein ailerons are disposed at the trailing edges of the front and rear wings near the wingtips, and wingtips winglets are disposed at the wingtips of the front and rear wings.

6. The fixed wing aircraft of claim 1, wherein the forward power plant is mounted at a leading edge, a trailing edge, above or below a forward wing; the rear power device is mounted at the front edge, the rear edge, above or below the rear wing.

7. The fixed-wing aircraft according to claim 1, wherein the forward and aft power plants are propellers driven by piston engines, rotor engines, turbine engines or electric motors, or are turbojet engines, turbofan engines, ducted fan engines.

8. A control method of a fixed wing aircraft as claimed in claim 1, wherein when the aircraft takes off, the front power device is started first, and the power generated by the front power device has a component force which is vertically upward, so that the aircraft nose is lifted upward after being taken off; along with the inclination of the machine body, the axes of the front power device and the rear power device are gradually deflected towards the vertical direction, and the component force of the power of the front power device in the vertical direction is gradually increased; when the axes of the front power device and the rear power device face or approach to the vertical direction, the rear power device is started, the tail is separated from the ground, and the front power device and the rear power device simultaneously generate upward power to vertically lift the airplane to a preset height.

9. A method for controlling a fixed-wing aircraft according to claim 1, wherein, after the aircraft is lifted off and is ready to cruise, the power generated by the front power device is smaller than that generated by the rear power device, the aircraft nose is gradually inclined downwards, the axes of the front power device and the rear power device are also gradually deflected towards the horizontal direction, the component force of the power of the front power device and the rear power device in the horizontal direction is gradually increased, the aircraft generates horizontal movement, and the front wing and the rear wing generate upward aerodynamic lift force; when the axes of the front power device and the rear power device become horizontal or close to horizontal, the front power device and the rear power device provide power for the airplane to fly horizontally during cruising, and aerodynamic lift force generated on the front wing and the rear wing maintains the airplane at a preset height.

10. A method for controlling a fixed wing aircraft as defined in claim 1, wherein when the aircraft is about to land, the power generated by the front power device is greater than that generated by the rear power device, the aircraft nose gradually changes from downward inclination to upward inclination, the axes of the front power device and the rear power device gradually deflect in the vertical direction, the component of the power of the front power device and the rear power device in the vertical direction gradually increases, the speed of the aircraft decreases, and the aerodynamic lift generated on the front wing and the rear wing also decreases; when the axes of the front power device and the rear power device become vertical, the airplane is in a hovering state, then the front power device and the rear power device synchronously reduce power, the airplane starts to vertically land, the tail of the airplane lands firstly, the rear power device stops working, the front power device continues to reduce power until the nose of the airplane also lands, and landing is completed.

Technical Field

The invention relates to the technical field of aviation aircrafts, in particular to a fixed-wing aircraft and a control method for realizing vertical take-off and landing and cruise flight of the fixed-wing aircraft.

Background

The fixed-wing aircraft has the advantages of high flying speed, large carrying capacity and the like, but cannot vertically take off and land and hover, and a special runway is required during taking off and landing, so that the application range of the fixed-wing aircraft is limited.

The gyroplane is contrary, and although the vertical take-off and landing and hovering can be realized, the requirement on the field is low, the flight speed is slow, the flight range is short, and the load capacity is small.

Fixed-wing aircraft have also emerged that combine the advantages of both of the above-mentioned aircraft to enable vertical take-off and landing. The implementation modes include the following modes:

one set of power device is used for vertical lifting, and the other set of power device is used for forward propulsion. For example, chinese patent CN211893638U discloses a distributed power water vertical take-off and landing aircraft, which includes a plurality of rotor power devices and a plurality of distributed power devices, respectively used for vertical take-off and landing and horizontal flight.

However, this solution, which simply and roughly superimposes two independent systems together, can generate serious complexity and instability, and the complexity of the architecture can bring a great risk to the control of the operation. In the cruise flight leveling stage, the power device for vertical take-off and landing is completely in an idle state, and even forms flight resistance. And the manufacturing cost is increased, the operation economic benefit is low, and the cost performance is not good.

And secondly, the conversion between vertical take-off and landing and horizontal propulsion is realized through the tilting of the power device. For example, chinese patent application CN112744352A discloses a distributed tilting multi-rotor aircraft and a flight control method, in which a distributed tilting power system is installed on a main wing and an auxiliary wing, and control in modes such as vertical take-off and landing and high-speed cruise is realized by tilting of multiple rotors. CN213354833U discloses a tilting vertical take-off and landing fixed wing aircraft, in which propellers are installed at both front and rear edges of wings, and the direction of the propeller is changed by adjusting the angle of the wing. The fixed wing aircraft with the tiltable duct disclosed in the Chinese patent application CN112340013A and the aircraft with the four-duct tilting layout disclosed in CN112896500A both adopt the tiltable duct power device.

However, in these schemes, regardless of the tilting of the rotor, the tilting of the wing or the tilting of the duct, the complexity of the power system and the difficulty of flight control are increased, the failure rate is high, and the reliability and the safety of the flight of the aircraft are greatly reduced.

In addition, the wing installation angle of a fixed-wing aircraft is generally small, the wing installation angle refers to the included angle between the chord line of the wing section at the wing root and the longitudinal axis of the aircraft body when the wing is installed on the aircraft body, and the installation angle of a common civil aviation passenger aircraft is about 4 degrees. If the installation angle is too large, the airplane can not take off due to too large resistance caused by too large attack angle during taxiing take off. During flight, sufficient lift cannot be obtained due to an excessively large angle of attack, and if the angle of attack at which the aircraft flies is greater than a critical angle of attack, the aircraft may stall. The critical attack angle of a common fixed-wing aircraft does not exceed 18 degrees, and because the fuselage is kept horizontal in the process of cruise flight, the wing installation angle of the conventional fixed-wing aircraft is far smaller than 18 degrees.

Disclosure of Invention

The invention aims to provide a fixed-wing aircraft which is higher in reliability, safety and economy and can take off and land vertically, so as to overcome the defects in the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme: a fixed wing aircraft capable of vertically taking off and landing comprises a front wing, a rear wing, a front power device and a rear power device, wherein the front wing and the rear wing are fixedly connected to an aircraft body, the front power device is installed on the front wing at a fixed angle, the rear power device is installed on the rear wing at a fixed angle, the installation angles of the front wing and the rear wing are both 20-60 degrees, and the included angles between the axial lines of the front power device and the rear power device and the longitudinal axis of the aircraft body are both 20-60 degrees.

Preferably, the front wings are fixedly connected to the left side and the right side of the front portion of the fuselage, the rear wings are fixedly connected to the left side and the right side of the rear portion of the fuselage, a fuselage inner cavity located in front of the front wings forms a nose cabin, a fuselage inner cavity located between the front wings and the rear wings forms a belly cabin, and a fuselage inner cavity located behind the rear wings forms a tail cabin.

Preferably, the length of the tail cabin is smaller than that of the head cabin.

Preferably, the front wing is fixedly connected to the front end of the fuselage and extends towards the left side and the right side, the rear wing is fixedly connected to the rear end of the fuselage and extends towards the left side and the right side, and the front wing, the rear wing and the fuselage are connected into an I shape.

Preferably, ailerons are arranged at the positions of the trailing edges of the front wing and the rear wing, which are close to the wingtips, and wingtips winglets are arranged at the wingtips of the front wing and the rear wing.

Preferably, the front power device is mounted at the front edge, the rear edge, above or below the front wing; the rear power device is mounted at the front edge, the rear edge, above or below the rear wing.

Preferably, the front power device and the rear power device are propellers driven by a piston engine, a rotor engine, a turbine engine or an electric motor, or are turbojet engines, turbofan engines and ducted fan engines.

The invention also provides a control method of the fixed wing aircraft, when the aircraft takes off, the front power device is started firstly, the power generated by the front power device has a vertically upward component force, so that the aircraft nose is separated from the ground firstly and is tilted upwards; along with the inclination of the machine body, the axes of the front power device and the rear power device are gradually deflected towards the vertical direction, and the component force of the power of the front power device in the vertical direction is gradually increased; when the axes of the front power device and the rear power device face or approach to the vertical direction, the rear power device is started, the tail is separated from the ground, and the front power device and the rear power device simultaneously generate upward power, so that the airplane is vertically lifted to a preset height and can be hovered.

After the airplane is lifted off and is ready to cruise and fly horizontally, the power generated by the front power device is smaller than that generated by the rear power device, the nose gradually inclines downwards, the axes of the front power device and the rear power device also gradually deflect towards the horizontal direction, the component force of the power of the front power device and the power of the rear power device in the horizontal direction is gradually increased, the airplane generates horizontal movement, and the front wing and the rear wing generate upward aerodynamic lift force; when the axes of the front power device and the rear power device become horizontal or close to horizontal, the front power device and the rear power device provide power for the airplane to fly horizontally during cruising, and aerodynamic lift force generated on the front wing and the rear wing maintains the airplane at a preset height.

When the airplane is ready to land, the power generated by the front power device is larger than that generated by the rear power device, the nose gradually inclines from downward inclination to upward inclination, the axes of the front power device and the rear power device gradually deflect towards the vertical direction, the component force of the power of the front power device and the rear power device in the vertical direction is gradually increased, the speed of the airplane is reduced, and the aerodynamic lift force generated on the front wing and the rear wing is also reduced; when the axes of the front power device and the rear power device become vertical, the airplane is in a hovering state, then the front power device and the rear power device synchronously reduce power, the airplane starts to vertically land, the tail of the airplane lands firstly, the rear power device stops working, the front power device continues to reduce power until the nose of the airplane also lands, and landing is completed.

Compared with the prior art, the invention has the following beneficial effects:

the invention develops a new method, breaks through the conventional method and innovatively provides the fixed-wing aircraft with the 'breakthrough-type installation angle'. The 'breakthrough-type mounting angle' means that the wing mounting angle in the invention is 20-60 degrees, which greatly deviates from the optional range of the wing mounting angle of the traditional fixed-wing aircraft. Meanwhile, the invention also provides a control method suitable for the fixed-wing aircraft with the breakthrough-type installation angle, and the fixed-wing aircraft can avoid the problem of overlarge wing attack angle caused by overlarge wing installation angle and realize vertical lifting in the flying process by controlling the flight in the take-off stage, the cruise stage and the landing stage.

The front power device and the rear power device are respectively arranged on the front wing and the rear wing, are both arranged on the front wing and the rear wing at a fixed angle, and are not provided with power devices with axes capable of tilting, so that the complexity and the failure rate of an aircraft power system are greatly reduced, and the reliability and the safety are improved. The power or the rotating speed of the front and rear power devices is adjusted, the airframe is tilted, and the attitude and the attack angle of the airframe are controlled and adjusted, so that the lift generated by the power devices and the aerodynamic lift generated by the wings are complementary, the overall lift of the airplane is continuous and stable, and the smooth transition of vertical take-off and landing and cruise flight can be realized.

The fixed wing aircraft has the advantages that the overall structure is highly simplified and solidified, the flight control mechanism is simple and reliable, the operation of the aircraft can be realized basically by adjusting the power or the rotating speed of the front and rear power devices, the one-key hovering function can be started at any time, and the safety and the reliability are greatly improved. The invention realizes the complete integration and unification of the power system and the lift system required by vertical take-off and landing, flight before cruising and maneuvering control, and has the absolute advantages of vertical take-off and landing, high cruising efficiency, long voyage, large load, simple manufacture, low cost, economical operation and the like.

Drawings

FIG. 1 is a perspective view of a vertical take-off and landing fixed wing aircraft according to the present invention.

FIG. 2 is a side view of a vertical take-off and landing fixed wing aircraft of the present invention.

FIG. 3 is a top view of a vertical take-off and landing fixed wing aircraft of the present invention.

FIG. 4 is a schematic perspective view of another embodiment of a VTOL fixed wing aircraft of the present invention.

Fig. 5 is a state in which the fixed-wing aircraft of the present invention is parked on the ground.

FIG. 6 is a schematic illustration of the attitude of the fixed wing aircraft of the present invention during vertical take-off and landing or hover.

Fig. 7 is a schematic illustration of the attitude of the fixed-wing aircraft of the present invention during cruise flight.

FIG. 8 is a schematic representation of the change in lift of the fixed-wing aircraft of the present invention from a hover state to a cruise level flight state.

Fig. 9 is a schematic diagram of the change in attitude of the fixed-wing aircraft during the process from vertical takeoff to cruise flight.

FIG. 10 is a schematic illustration of the change in attitude of the fuselage of a fixed-wing aircraft of the present invention during a transition from cruise level flight to vertical descent.

The labels in the figure are:

1. fuselage 2, front wing 3 and rear wing

4. Front power device 5, rear power device 10 and longitudinal axis of machine body

11. Nose cabin 12, belly cabin 13 and tail cabin

20. Front wing profile chord line 21, front wing aileron 30, rear wing profile chord line

31. Aft wing aileron 40, forward power plant axis 50, aft power plant axis

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and are not intended to limit the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

As shown in fig. 1, the fixed wing aircraft capable of vertically taking off and landing of the present invention includes a front wing 2 and a rear wing 3 fixedly connected to a fuselage 1, the front wing 2 is fixedly connected to the left and right sides of the front portion of the fuselage 1, the rear wing 3 is fixedly connected to the left and right sides of the rear portion of the fuselage 1, a flight control system and a sensor or a detection instrument for detecting the posture of the fuselage are arranged in the fuselage 1, and the sensor or the detection instrument is connected to the flight control system. As shown in fig. 3, in one embodiment of the invention, the fuselage cavity located in front of the front wing 2 forms a nose cabin 11, the fuselage cavity located between the front wing 2 and the rear wing 3 forms a belly cabin 12, and the fuselage cavity located behind the rear wing 3 forms a tail cabin 13. The aircraft nose cabin 11 can be provided with an airborne device and a flight control system; a cockpit and a load cabin are arranged in the ventral cabin 12, and a fuel tank or a battery pack can be arranged at the same time; and a take-off and landing sensor can be deployed in the tail cabin 13, and the design is strengthened according to special take-off and landing requirements. An aileron 21 is arranged at the rear edge of the front wing 2 close to the wingtip, and an aileron 31 is arranged at the rear edge of the rear wing 3 close to the wingtip for controlling the speed and the rolling. Wingtip winglets can be arranged at the wingtips of the front wing and the rear wing to reduce induced resistance. Wingtip winglets are well known structures and are not shown.

The front wing and the rear wing can also be arranged at two ends of the fuselage, as shown in fig. 4, the front wing 2 is fixedly connected at the front end of the fuselage 1 and extends towards the left and the right sides, the rear wing 3 is fixedly connected at the rear end of the fuselage 1 and extends towards the left and the right sides, so that the front wing 2, the rear wing 3 and the fuselage 1 are connected into an I shape, and the inner cavity of the fuselage is not divided into a head cabin, a belly cabin and a tail cabin.

The power devices are arranged on the front wing and the rear wing, as shown in figure 1, the front power device 4 is arranged on the front wing 2 at a fixed angle, and the rear power device 5 is arranged on the rear wing 3 at a fixed angle. According to the requirement, the number of the front power device and the rear power device can be more than one, for example, 2, 4 or 6, and the number of the front power device 4 and the number of the rear power device 5 in fig. 1 are both 4. And the front power device and the rear power device are connected with a flight control system.

Although the power plant shown in fig. 1 is a power plant with propellers (or rotors), the front power plant 4 and the rear power plant 5 in the present invention are not limited thereto, and may be propellers driven by piston engines, rotary engines, turbine engines or electric motors, or known aircraft power plants such as turbojet engines, turbofan engines, ducted fan engines, etc., for example, fig. 2 shows the front and rear power plants 4, 5 without propellers (or rotors). The mounting position of the power plant on the wing can be different according to the type of the power plant, for example, the front power plant 4 can be mounted on, above or below the leading edge or the trailing edge of the front wing 2; the rear power means 5 is mounted at, above or below the leading or trailing edge of the rear wing 3. However, no matter where the wing is installed, the installation angle of the front power device and the rear power device is fixed, and the axis of the front power device and the axis of the rear power device do not need to be tilted.

One important difference between the present invention and the prior art is that the stagger angle of the front wing and the rear wing breaks the conventional angle. As shown in fig. 2, the angle between the chord line 20 of the airfoil at the root of the front wing 2 and the longitudinal axis 10 of the fuselage is the stagger angle of the front wing, and the angle between the chord line 30 of the airfoil at the root of the rear wing 3 and the longitudinal axis 10 of the fuselage is the stagger angle of the rear wing. In the invention, the mounting angles of the front wing and the rear wing are both 20-60 degrees, which is far larger than the wing mounting angle of the existing fixed-wing aircraft. In the embodiment shown in fig. 2, the erection angles of the front wing and the rear wing are the same and are both α, that is, α is between 20 and 60 degrees, and in this embodiment, α is preferably 30 to 45 degrees, and this angle range can better balance the take-off and landing efficiency and the inclination angle and the wind resistance of the fuselage during cruise flight.

The front power unit 4 and the rear power unit 5 are mounted at a fixed angle to the front wing 2 and the rear wing 3, respectively, and may generate a forward and upward pulling or pushing force on the aircraft depending on the type of the front and rear power units 4, 5. In the present application, the pulling or pushing forces generated by the front and rear power units 4, 5 are collectively referred to as "power", and the line of action of the "power" is referred to as the "axis" of the front and rear power units. In the invention, the included angle between the axis 40 of the front power device and the longitudinal axis 10 of the fuselage is a fixed value and is between 20 and 60 degrees; the angle between the axis 50 of the rear power unit and the longitudinal axis 10 of the fuselage is also constant and is between 20 and 60 degrees. In the embodiment shown in fig. 2, the included angles between the axis 40 of the front power device and the axis 50 of the rear power device and the longitudinal axis 10 of the fuselage are the same, and are both beta, namely, beta is between 20 and 60 degrees, in the embodiment, beta is preferably 30 to 45 degrees, and the angle range can better take the taking-off and landing efficiency and the inclination angle of the fuselage during the cruise flight into consideration.

In the preferred embodiment of the invention, the front wing profile chord line 20 is approximately parallel to the front power plant axis 40 but at a slight angle (e.g. 3-5 °), and the rear wing profile chord line 30 of the rear wing 3 is approximately parallel to the rear power plant axis 50 but at a slight angle (e.g. 3-5 °), i.e. a is slightly larger than β.

The wing installation angle adopted by the invention is very large, and if the sliding takeoff is carried out according to the traditional fixed wing airplane mode, the resistance is too large, so that enough lift force cannot be obtained, and the takeoff cannot be carried out; if the cruise flight is carried out in a manner of a conventional fixed wing aircraft with the fuselage kept substantially horizontal, a stall may also occur due to an excessively large angle of attack. Therefore, the present invention requires a special flight control mode.

The control method of the fixed-wing aircraft of the present invention is explained below.

As shown in FIG. 5, before taking off, the fixed wing aircraft of the present invention has a horizontal fuselage on the ground. During taking off, the front power device 4 is started firstly, the power generated by the front power device 4 inclines upwards along the direction of the axis 40, namely, the power forms an angle of 20-60 degrees with the horizontal line, the power has a component force which is vertically upwards, the machine head can be separated from the ground firstly and upwards tilted, and as shown in fig. 6, the machine body is in an inclined state. In order to avoid the situation that the tail touches the ground when the fuselage inclines, the tail cabin can be set to be shorter, so that the length of the tail cabin is smaller than that of the nose cabin. Along with the gradual inclination of the fuselage 1, the included angle gamma between the longitudinal axis 10 of the fuselage and the horizontal plane is gradually increased, the axes 40 and 50 of the front power device and the rear power device are also gradually deflected towards the vertical direction, and therefore the power component of the front power device 4 in the vertical direction is gradually increased; when the included angle gamma between the longitudinal axis 10 of the airplane body and the horizontal plane is close to, equal to or slightly exceeds 90-beta (namely, gamma and beta are complementary), namely, the axes 40 and 50 of the front power device and the rear power device are both towards or are close to towards the vertical direction, the rear power device 5 is started, the airplane tail is also separated from the ground, and the front power device 4 and the rear power device 5 simultaneously generate upward power, so that the airplane body keeps the inclined state and is vertically lifted to the preset height.

After the aircraft is lifted off, if the lift force generated by the front and rear power devices is equal to the weight of the aircraft, the aircraft can be in a hovering state (as shown in fig. 6) with the inclined fuselage, at this time, because the axes 40 and 50 of the front and rear power devices face the vertical direction and no power in the horizontal direction is generated, the aircraft cannot generate movement in the horizontal direction, and the front and rear wings cannot generate aerodynamic lift force.

When the airplane is ready to cruise and fly horizontally in the air, the power generated by the front power device 4 is smaller than that generated by the rear power device 5, the nose gradually inclines from the upward inclination to the downward inclination, as shown in fig. 7, the axes 40 and 50 of the front power device and the rear power device gradually deflect from the vertical direction to the horizontal direction, the component force of the power of the front power device 4 and the power of the rear power device 5 in the horizontal direction gradually increases, and the component force in the vertical direction gradually decreases; the airplane generates horizontal movement, so that upward aerodynamic lift is generated on the front wing and the rear wing, and the deficiency of lift caused by the reduction of the component force of power in the vertical direction can be made up. When the axes 40, 50 of the front and rear power devices become horizontal or close to horizontal, the front power device 4 and the rear power device 5 provide power for the aircraft to cruise, and because alpha is slightly larger than beta, the attack angles of the front and rear wings 2, 3 are consistent with that of the conventional fixed wing aircraft during cruise, and the aerodynamic lift generated on the front and rear wings 2, 3 is enough to maintain the aircraft at a preset height. Thus, the aircraft can tilt the fuselage by almost 90 degrees from a hover state after lift-off to a cruise flight state (fig. 6-7), and a significant feature of the present invention is the tilting of the fuselage from vertical lift-off to cruise flight. A center of gravity stabilization mechanism may be provided in the fuselage to promote stability of flight. The plane always maintains the state that the nose is inclined downwards as shown in fig. 7 when in cruising and flat flight, which is one aspect of the invention that the invention has obvious difference from the traditional fixed wing plane in flight attitude, if carrying people, a cockpit automatic synchronous horizontal balance system and a seat automatic adjusting system can be arranged to automatically adapt to the change of the attitude of the plane body.

Fig. 8 shows the trend of the lift force during the transition from the hovering state to the cruise flight state of the aircraft. The horizontal axis represents the angle of the axes of the front and rear power units with respect to the vertical direction, the vertical axis represents lift force, f1 represents lift force generated by the front and rear power units (i.e., component force of power in the vertical direction), f2 represents aerodynamic lift force generated on the wing, and f represents the resultant force of f1 and f 2. Of course, these forces do not necessarily change linearly, but fig. 8 is only for the purpose of visually showing the complementary relationship of f1 and f2 when changing, and the aircraft can obtain a relatively stable resultant lift force f due to the complementary changes of f1 and f 2.

Fig. 9 shows in a more intuitive manner the change in attitude of the fixed-wing aircraft from vertical takeoff to cruise flight of the invention, with the left end representing the nose and the right end representing the tail.

The process from cruise flight to landing of the airplane is equivalent to the reverse process from vertical takeoff to cruise flight.

When the airplane is going to land in a cruising and level flying manner to a destination, the power generated by the front power device is larger than that generated by the rear power device, the nose gradually inclines from downward to upward, the axes of the front power device and the rear power device gradually deflect towards the vertical direction, namely the state shown in figure 7 is changed into the state shown in figure 6, the component force of the power of the front power device 4 and the power of the rear power device 5 in the vertical direction gradually increases, the level flying speed of the airplane decreases, and the aerodynamic lift force generated on the front wing and the rear wing also decreases; when the axes 40 and 50 of the front power device and the rear power device become vertical, the airplane is in a hovering state, then the front power device 4 and the rear power device 5 synchronously reduce power, the airplane starts to vertically land, the tail of the airplane lands firstly, the rear power device 5 stops working, the front power device 4 continues to reduce power until the nose of the airplane also lands, the landing is completed, and the state shown in fig. 5 is returned.

Fig. 10 shows in a more intuitive manner the change in attitude of the fixed-wing aircraft of the invention from cruise flight to vertical landing, with the left hand side representing the nose and the right hand side representing the tail.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and substitutions can be made without departing from the technical principle of the present invention, and these modifications and substitutions should also be regarded as the protection scope of the present invention.