CLOSED-WING VERTICAL TAKE-OFF AND LANDING AIRCRAFT

Technical Field

The invention belongs to the field of aviation, namely to the design of closed-wing vertical take-off and landing aircraft, which can be used to deliver cargo or transport passengers.

Background Art

The use of a closed wing in aircraft designs allows to improve aerodynamic parameters by reducing the intensity of lift-induced vortices, which cause lift-induced drag, and also enhances the strength and stiffness of the aircraft frame since the front and rear wings are connected and work as a whole, not as independent elements. One way to perform vertical takeoff and landing is to use thrust vectoring, which provides the necessary thrust in the vertical direction during takeoff and landing, and in the horizontal direction during cruise flight. This approach has been applied in the present invention.

A patent application [1] discloses a closed-wing vertical take-off and landing aircraft comprising a fuselage, first and second front wing planes mounted to the fuselage, a rear wing consisting of first and second rear wing planes and a central static connecting portion, a first wing connecting member expanding between the first front wing plane and the rear wing, and between the second front and rear wing planes, wherein the rear wing is attached to a V-shaped tail consisting of first and second angularly inclined arms, two electric motors with rotors located on each of the wing planes, each rotor is pivotal between the configurations for vertical and forward flight.

The disadvantage of this aircraft design is that in the horizontal flight mode, the aircraft roll and pitch control is carried out exclusively by tilting the two engines together with the rear part of the wing planes. This reduces the system’s reliability, since jamming the deflection mechanism of any of the engines will lead to the loss of controllability of the entire section. Furthermore, the aircraft control system's dynamic characteristics deteriorate due to heavy moving elements. An aircraft permitting a smooth transition between vertical and horizontal flight disclosed in [2] comprises a fuselage, a closed wing comprising front and rear wing planes, and winglets connecting these planes, as well as a vertical stabilizer and a pair of tilt-wings pivotably mounted to the central portion of the fuselage. Each tiltwing is coupled with a thruster. In the take-off mode, the tilt-wing is directed so that the rotary wings create thrust in the vertical direction, as required for vertical take-off, then the tilt-wings with the thrusters gradually return to the position in which the thrust required for horizontal flight is created.

One drawback of the aircraft described above is low redundancy. The aircraft contains two engines (one on each side), and a failure of one of them cannot be compensated for in the take-off mode. Furthermore, this aircraft has low maneuverability characteristics due to the lack of control surfaces on the wings.

The aircraft closest to the present invention is a hybrid vertical take-off and landing aircraft with vehicle assist [3], comprising a fuselage, a V-shaped tail and a closed box wing containing front and rear wing planes and side elements, which connect the end parts of the planes. The front wing planes are attached to the nose, and the rear wing planes are attached to the tail. Each plane contains beams on which rotors are mounted. All rotors, except for the two located on the rear wing planes, are oriented to create thrust only in the vertical direction. The two rotors on the rear wing plane are installed in the beam through a rotary mechanism that changes the thrust direction. Thus, during vertical take-off all thrusters create thrust in the vertical direction, then the two thrusters gradually deflect to a horizontal position, creating the thrust required for cruise flight.

One disadvantage of this aircraft is low redundancy related to the yaw movement during a cruise flight. It is impossible to maintain yaw controllability by changing thrust if one of the two tilting rotors fails.

Disclosure of Invention

The primary object of the present invention is to provide a vertical take-off and landing aircraft having high controllability, static stability and redundancy, as well as aerodynamically efficient flight in cruising and transition modes.

The object is achieved in a closed-wing vertical take-off and landing aircraft comprising: a fuselage; a tail unit comprising two angularly inclined stabilizers; and a closed wing, comprising a front wing formed by two planes mounted to the fuselage, a rear wing, formed by two planes mounted to the tail unit, side elements connecting the outer sides of the front and rear wing planes; at least two propeller-type thrusters connected to each of the front wing planes by beams pointing toward the rear wing such that said thrusters generate vertical thrust, the closed wing additionally contains a central part of the rear wing, which, together with the two stabilizers of the tail unit and the rear part of the fuselage, form a closed contour; elevons are installed on the rear edges of the rear wing planes; propeller-type thrusters are connected through rotary mechanisms to at least two beams attached to each of the rear wing planes, said beams pointing toward the front wing, such that said thrusters generate both vertical and horizontal thrust.

Because all thrusters of the rear wing planes are installed on beams through the rotating mechanisms, it is possible to change the thrust direction. Thus, the thrusters of the rear wing planes generate thrust in the vertical direction during takeoff/landing and in the horizontal direction during cruise flight. During vertical take-off, high controllability of yaw, roll and pitch is achieved by varying the thrusters’ operating modes. During cruise flight, high pitch and roll controllability is ensured by using wing control surfaces, namely elevons installed on the rear edges of the rear wing planes. Yaw controllability is ensured by varying the operating modes of the rear wing plane thrusters. Since the thrusters are open propellers removed from the wing airfoil, this design allows for a smooth flow over the front and rear wing airfoils in the transition and cruise flight modes, thereby ensuring high aerodynamic parameters. Using a closed-wing structure reduces the intensity of wingtip vortices and, therefore, aerodynamic drag. High redundancy is ensured by the presence of at least four tilting thrusters installed on the rear wing beams. A failure of one of the thrusters is recoverable: pitch, roll and yaw will remain controllable in all flight modes.

A closed contour is formed between the tail unit, the rear part of the fuselage and the central part of the rear wing. Choosing the angles of incidence of the tail unit and the central part of the rear wing at the design stage allows for ensuring the required parameters of the airflow through the said closed contour, thereby achieving appropriate redistribution of aerodynamic forces between the main elements of the airframe and obtaining the required static stability and the position of the center of pressure. Brief Description of Drawings

The essence of the proposed invention is explained by the drawings, in which:

Fig. 1 is a top view of the aircraft;

Fig. 2 is a front view of the aircraft;

Fig. 3 depicts a beam of the rear wing plane with the rotary mechanism and the thruster in the cruising position;

Fig. 4 depicts a beam of the rear wing plane with the rotary mechanism and the thruster in the take-off position;

Fig. 5 is a three-dimensional view of the aircraft in cruise flight.

Fig. 6 is a three-dimensional view of the aircraft during takeoff/landing.

The closed-wing vertical takeoff and landing aircraft comprises a fuselage 1 , a tail unit comprising two angularly inclined stabilizers 12, a closed wing, comprising a front wing formed by two planes 2 mounted to the fuselage 1 and a rear wing, formed by two planes 3 mounted to the tail unit, side elements 5 connecting the outer sides of the front wing planes 2 and rear wing planes 3. At least two propeller-type thrusters 8 are attached to each of the planes of the front wing by beams 7 pointing toward the rear wing in the position to generate vertical thrust. The closed wing additionally contains a central part 4 of the rear wing, which, together with the two tail unit stabilizers 12 and the rear part of the fuselage, form a closed contour 11 . Elevons 6 are installed on the rear edges of the rear wing planes 3. At least two beams 10 pointing toward the front wing are attached to each of the rear wing planes 3. Propeller-type thrusters 9 are mounted on the beams 10 through rotary mechanisms 14. The thrusters 9 generate both vertical thrust during takeoff/landing and horizontal thrust during cruise flight.

The closed contour 11 formed by two angularly inclined stabilizers 12, the rear part of the fuselage 1 and the central part 4 of the rear wing has higher rigidity than a structure with a single vertical stabilizer or without a central part 4 of the rear wing 3. This positively affects load transfer from the rear wing 3 to the fuselage 1. On the other hand, adjusting the incidence angles of the stabilizers 12 and the incidence angle of the central part 4 of the rear wing allows to attain the required parameters of the airflow through the closed contour 11 and, as a result, to achieve the desired lift distribution between the wing planes, as well as the required static stability parameters.

Description of Embodiments

After a vertical take-off, the rotary mechanisms 14 gradually deflect the thrusters 9 of the rear wing planes 3 relative to the pivot point 13 to change the thrust vector from vertical to horizontal. Thus, they provide the required vertical thrust during take- off/landing, and horizontal thrust during cruise flight. After transitioning to the cruise flight mode, yaw control is provided by the differential thrust of the thrusters 9. Using at least two thrusters on each wing plane allows for maintaining yaw control in case of a single failure of any of the thrusters 9.

The elevons 6 are designed to increase the rear wing lift during transition flight modes, and to control the aircraft roll and pitch in the cruising flight mode. Additional roll and pitch controllability in case of a failure of one or both elevons can be ensured by changing the thrust direction of the thrusters 9 by adjusting the deflection angle using the rotary mechanism 14.

The present closed-wing vertical takeoff and landing aircraft functions as follows. The aircraft is placed on a horizontal stationary surface, the thrusters 9 are set to the vertical position to generate thrust in the vertical direction. Due to the simultaneous operation of the thrusters 8 and 9, the aircraft takes off vertically. After reaching a sufficient altitude, the rotary mechanism 14 gradually deflects the thrusters 9 of the rear wing 3 to generate thrust in both vertical and horizontal projections. At the same time, the elevons 6 are deflected downwards so that the rear wing 3 generates the required lift at a low horizontal flight speed. Next, as the horizontal speed increases, the elevons 6 are gradually deflected back to the neutral position, while the thrusters 9 are deflected to the horizontal position, in which the thrust required for cruise flight is created. In the final part of the flight, the aircraft reduces the horizontal speed, and the procedure is performed in reverse order. The elevons 6 are gradually deflected downwards, while the thrusters 9 are gradually deflected to the vertical position. Vertical landing is performed when the horizontal speed decreases to zero and the aircraft hovers in the air. At this point, the position of the aircraft can be adjusted so it can land exactly in a designated location by deflecting the thrusters 9 to a small extent and by varying modes of operation of thrusters 8 and 9. The proposed closed-wing vertical take-off and landing aircraft can perform safe flight in case of failure of any of the thrusters or elevons and is reliably controllable for yaw, roll and pitch in all flight modes thanks to the position of the elements, the advantageous configuration of the power and control elements, namely, at least two thrusters on the rear wing planes capable of changing the thrust vector from vertical in take-off mode to horizontal in cruise flight mode, two elevons, as well as the thrusters attached to the front wing.

References

1. WO2022056597A1 ; B64C1/26, B64C1/10, B64C29/00; Aircraft structure / Andrew Dudley Moore, Alfred Leonard Swallow / AMSL INNOVATIONS PTY

LTD [AU]. - appl. AU2020903348A, 18.09.2020. - publ. 24.03.2022.

2. W02015200345A1 ; B64C27/28; Five-wing aircraft to permit smooth transitions between vertical and horizontal flight / Garreau Oliver [US]. - appl. US2015037221 W, -23.06.2015. - publ. 30.12.2015. 3. WO2019211875A1 ; B64C27/28; B64C29/00; B64C39/08; Hybrid vertical takeoff and landing (vtol) aircraft with vehicle assist / Anthony Alvin [IN], - appl. IN2019050354W, 02.05.2019. - publ. 07.11.2019.