CN111516869A - Layout and control method of a tilt-rotor-wing vertical take-off and landing aircraft - Google Patents

Abstract

The invention relates to a layout and a control method of a tilt rotor wing-wing vertical take-off and landing aircraft. The wings and the rotor wings can rotate in a certain angle range around the rotating shaft penetrating through the inner parts of the wings, and the rotor wings can rotate in a tilting mode respectively. The control method of the invention can lead the aircraft to realize vertical take-off and landing and high-speed flat flight, and can respectively and properly adjust the angles of the rotor wing and the wing at each stage of the flight, thereby optimizing the overall efficiency of the aircraft. The rotor wing and the wing can be respectively tilted, the resistance is small in the vertical take-off and landing stage, and the air flow interference between the rotor wing and the wing is small; when the aircraft is converted between vertical take-off and landing and flat flight, the utilization efficiency of the wings is high, the load of a power system is low, and the flight control in the whole flight process is simpler, so that the aircraft is a vertical take-off and landing aircraft with wide application prospect.

Description

Layout and control method of a tilt-rotor-wing vertical take-off and landing aircraft

technical field

The invention relates to a layout and control method of a tilt-rotor-wing vertical take-off and landing aircraft, in particular to a layout and control method of a vertical take-off and landing aircraft in which the rotor and the wing can be tilted respectively, belonging to the field of aviation technology.

Background technique

Vertical take-off and landing aircraft can take off and land vertically like a helicopter, without the constraints of a runway, and can fly at high speed like a fixed-wing aircraft. It combines the advantages of both fixed-wing aircraft and helicopters. application prospects.

At present, there are mainly the following types of vertical take-off and landing aircraft. The first is a vertical take-off and landing fighter aircraft represented by "AV-8B" and "F-35" that uses lift fans or vector nozzles to provide vertical take-off and landing power, and the second is a tilting fighter represented by "V-22". Gyrocopter, the third type is a composite vertical take-off and landing aircraft based on the existing helicopter and additional accessories such as forward power, and the fourth is a tilt-wing vertical take-off and landing aircraft represented by "GL-10". All of them have successfully achieved the design purpose of vertical take-off and landing aircraft, and some of them have been put into practical use.

However, these existing vertical take-off and landing vehicles have some problems. In the first two vertical take-off and landing aircraft, the upper surface of the wing is perpendicular to the direction of the incoming flow, and the windward area is too large, which will generate a large pressure differential resistance. In the second type of tilt-rotor aircraft, since the rotor is just above the wing during the vertical take-off and landing stage, the slip flow from the rotor will directly act on the upper surface of the wing, which will generate turbulent flow and affect the control of the aircraft. The third type of vertical take-off and landing aircraft uses a large amount of power to drive and control the main rotor, which is not the main source of lift during high-speed flight. The fourth type of tilt-wing vertical take-off and landing aircraft, the angle between the rotor and the wing is fixed, and the wing drives the rotor to tilt together, reducing the windward area of the aircraft during the vertical take-off and landing stage, and avoiding the gap between the rotor and the wing. mutual interference. However, during the modal transition from vertical take-off and landing to level flight, this type of aircraft has the problems of poor aerodynamic conditions of the wings and insufficient lift and rudder efficiency, resulting in insufficient use of the wings. At the same time, this also requires the power system not only to have sufficient margin to provide control force, but also to ensure that there is enough vertical power component to offset the aircraft's own gravity during the tilting process, which seriously increases the burden on the power system.

To sum up, the existing vertical take-off and landing aircraft have the problems of large resistance in the vertical take-off and landing stage, serious airflow interference between the rotor and the wing, and complicated control. , The problem of heavy burden on the power system and complex control requires a model that can not only reduce the airflow interference between the rotor and the wing during the vertical take-off and landing stage, but also can lift the aircraft.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a layout and control method of a tilting rotor-wing vertical take-off and landing aircraft, when the aircraft is switched between the vertical take-off and landing mode and the level flight mode, the rotor and the wing are tilted respectively, and the aircraft is improved. The utilization efficiency of the wing reduces the interference between the wing and the rotor, and reduces the burden on the rotor.

The basic idea of the present invention is as follows: the whole aircraft adopts a tandem wing layout, the wings are divided into two groups, front and rear, and the wingspan of the front and rear wings are the same. The front and rear of the fuselage are provided with front and rear shafts, which protrude to both sides of the fuselage. There is a shaft hole in the wing, which can be respectively sleeved on the front and rear shafts and rotated around the shaft. There are one set at the left and right ends of each rotating shaft, and there are four sets of rotors in total, which constitute the power system of the aircraft. They can be rotated around the axis on which they are located to change the direction of pull. This achieves the design goal of tilting the rotor and the wing separately. In the vertical take-off and landing mode, the wings are in a vertical position, and the rotors are also in a vertical state to provide upward power to make the aircraft climb vertically, and control the aircraft through the rotor power differential caused by the speed difference between the four sets of rotors Attitude; when it climbs to a certain height, the wing gradually tilts to be horizontal, and the rotor gradually tilts forward slightly, so that the aircraft has a certain forward flight speed, and through the rotor power differential and the aerodynamic rudder surface on the wing Control the attitude of the aircraft; when the aircraft has sufficient forward flight speed, the rotor is completely turned to the horizontal position, the aircraft enters the level flight mode, and the aircraft attitude is controlled by the rotor power differential and the aerodynamic rudder surface. When the aircraft is about to land, the rotor gradually turns to the vertical position to reduce the forward flight power, reduces the forward flight speed of the aircraft through air resistance, and controls the aircraft attitude through the rotor power differential and aerodynamic rudder; In the straight position, the wings quickly turn to the vertical position, and the forward flight speed is quickly reduced to 0 by increasing the windward area. At this time, the aircraft enters the vertical take-off and landing mode, and the aircraft can land vertically.

The layout of a tilt-rotor-wing vertical take-off and landing aircraft includes: a fuselage, a wing, a rotating shaft, a rotor, and electronic equipment.

The fuselage is the main part of the aircraft, carrying the payload and connecting various other parts of the aircraft.

The wings are divided into front and rear groups, which are respectively connected to the fuselage through two rotating shafts arranged at the front and rear of the fuselage, and can be rotated around the corresponding rotating shafts in the range of 0° to 90°, and are used for generating in level flight mode. lift. Aerodynamic control surfaces are provided on the wings to provide control of the aircraft. There is a shaft hole in the wing, which can completely wrap the shaft in the wing.

There are two described rotating shafts, which are respectively fixed at the front part and the rear part of the fuselage, as the rotating shaft of the rotor at both ends of the wing and the wing, which bears the load produced by the two and transfers the load to the fuselage. The shaft is hollow, and equipment such as wires can be arranged inside it.

The rotors are arranged at the wingtips on both sides of the front and rear wings, that is, the ends of the front and rear two rotating shafts. There are four groups in total, which constitute the power system of the aircraft, which is used to provide the power of the aircraft, using the speed differential belt between the four groups of rotors. The incoming rotor power differential provides the control force. They can be rotated from 0° to 90° around the shaft on which they are installed, and the wires are passed through the hollow shaft to connect to the electronics inside the fuselage.

The electronic equipment is arranged in the fuselage, including batteries, flight controllers, signal receivers, etc., for providing energy, controlling the attitude of the aircraft, receiving control commands, etc., to ensure that the aircraft can fly normally as designed.

A control method for a tilt-rotor-wing vertical take-off and landing aircraft, including control methods in the following four modes: vertical take-off and landing mode, vertical take-off and landing-turn-level flight mode, level-flight mode, and level-to-vertical take-off and landing mode . The specific control method is as follows:

In the vertical take-off and landing mode, the wing is in a vertical state, and the rotor is in a vertical state. The rotors now provide upward power, allowing the aircraft to climb vertically. Control is provided by differential rotor power.

Described vertical take-off and landing turns level flight mode, wing is turned into horizontal state gradually by vertical state, rotor is turned into horizontal state gradually by vertical state, is divided into four steps altogether:

Step 1: The wing starts to tilt gradually to the horizontal state, the rotor does not move, and the power is used to offset the weight of the aircraft. At the same time, through the power differential of the front and rear rotors, the aircraft has a certain negative pitch angle, so that the aircraft has a forward power component, and the forward flight speed of the aircraft is improved. In this step, the rotor power differential is used to provide the control force of the aircraft;

Step 2: When the aircraft reaches a certain forward flight speed, the wings will tilt to a certain angle to ensure that the wings can provide greater lift. At this time, the rotors begin to tilt to a horizontal state. This will increase the forward power component of the rotor, so that the forward flight speed of the aircraft will be further improved. At the same time, the lift provided by the wing will also increase with the increase of the forward flight speed, offsetting the vertical decrease due to the tilt of the rotor. The dynamic component of the direction. In this step, the rotor power differential is mainly used to provide control force, and the aerodynamic rudder surface can be used as an auxiliary;

Step 3: In order to ensure that the aircraft has a normal flight attitude in level flight, that is, the aircraft has a positive pitch angle, the wings and rotors will be tilted synchronously until the wings are completely turned to the horizontal position, and the aircraft reaches the pitch of normal level flight. horn. At this time, when the forward flying speed reaches a certain value, the wing can already provide most of the lift, and the rotor does not need to provide a large vertical component to offset its own gravity. In this step, the rotor power differential is mainly used to provide control force, and the aerodynamic rudder surface can be used as an auxiliary;

Step 4: The rotor is completely turned to the horizontal state, only forward power is provided, and the aircraft enters the level flight mode. At this time, the wings can provide all the lift, which can completely offset the weight of the aircraft. In this step, the aerodynamic rudder surface is mainly used to provide control force, and the rotor power differential can be used as an auxiliary.

In the level flight mode, both the wing and the rotor are in a horizontal state. The rotor provides forward power, and the wings provide upward lift to offset the weight of the aircraft, allowing the aircraft to fly at high speed. The aircraft mainly provides the control force through the aerodynamic rudder surface arranged on the wing, and provides the yaw moment through the rotor power differential.

Described horizontal flight turns vertical take-off and landing mode, the rotor gradually changes from the horizontal state to the vertical state, and the airfoil gradually changes from the horizontal state to the vertical state, which is divided into three steps:

The first step: the rotor gradually tilts from the horizontal state to the vertical state, and the wing is in the horizontal state. At this time, the forward flight speed is still large, and the wings still provide most of the lift, which offsets the weight of the aircraft together with the vertical power component of the rotor. In this step, the aerodynamic rudder surface is mainly used to provide control force, and the rotor power differential can be used as an auxiliary;

Step 2: The rotor is fully turned to the vertical state, and the wing is in a horizontal state. At this time, due to air resistance and other relations, the forward flight speed of the aircraft has dropped significantly, the wings can no longer provide enough lift, and the aerodynamic rudder surface is not enough to provide enough control. At this time, the rotor has been turned to a vertical state, and the power can be fully used to offset the weight of the aircraft. In this step, the rotor power differential is used to provide the control force;

Step 3: The rotor is in a vertical state, and the wing is quickly turned from a horizontal state to a vertical state. In the previous step, although the forward flying speed has dropped significantly, it is not yet zero. At this time, the lift provided by the wings is very small, and the aircraft no longer needs to rely on the wings to offset its own weight. At this time, the wing changes from the horizontal state to the vertical state rapidly, which can rapidly increase the forward windward area of the aircraft, which acts as a drag plate, and reduces the forward flight speed to 0 rapidly, and the aircraft enters the vertical take-off and landing mode. And because the rotor can provide sufficient control at this time, it will not have an excessive impact on the flight attitude of the aircraft. In this step, the rotor power differential is used to provide the control force.

The advantages of the present invention are:

1. the present invention has little windward area of the wing in the vertical take-off and landing stage, and the projected area on the rotor paddle is little, reduces the flight resistance, reduces the airflow interference and the control difficulty between the rotor and the wing. This solves the problems of large windward area, large flight resistance, and turbulent flow between the rotor slipstream and the wing during the vertical take-off and landing stage of traditional vertical take-off and landing aircraft.

2. The wing and the rotor in the tilt-rotor-wing vertical take-off and landing aircraft of the present invention can be tilted respectively, and the corresponding control method can be relied on when the vertical take-off and landing mode and the level flight mode are converted, and the aerodynamic performance of the wing can be effectively utilized , improve the utilization efficiency of the wing, reduce the burden and control difficulty of the power system. This solves the problems of low wing aerodynamic efficiency and low wing utilization efficiency when the traditional vertical take-off and landing aircraft switches between the vertical take-off and landing mode and the level flight mode, and also solves the complex flight control in the process and the overburden of the power system. The problem.

Description of drawings

FIG. 1 is an axonometric view of an aircraft according to an embodiment of the present invention;

Fig. 2 is the three views of the aircraft of the embodiment of the present invention;

Figure 3 is a schematic diagram of the vertical take-off and landing mode of a tilt-rotor-wing vertical take-off and landing aircraft;

Figure 4 is a schematic diagram of a tilt-rotor-wing vertical take-off and landing aircraft vertical take-off and landing rotation level flight mode;

FIG. 5 is a schematic diagram of a tilt-rotor-wing vertical take-off and landing aircraft in level flight mode;

FIG. 6 is a schematic diagram of a tilt-rotor-wing vertical take-off and landing aircraft in a horizontal-to-vertical take-off and landing mode.

The symbols in the figure are explained as follows:

1. Fuselage 2. Wing 3. Shaft

4. Rotor 5. Electronic equipment

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. These drawings are all simplified schematic diagrams, and only illustrate the basic structure of the present invention in a schematic manner.

A layout of a tilt-rotor-wing vertical take-off and landing aircraft, as shown in Figures 1 and 2, includes: a fuselage 1, a wing 2, a rotating shaft 3, a rotor 4, and an electronic device 5.

Airframe 1 is the main part of the aircraft, carrying the payload and connecting various other parts of the aircraft.

The wing 2 is divided into two groups, front and rear, which are respectively connected to the fuselage 1 through two rotating shafts 3 arranged in the front and rear of the fuselage 1, and can be rotated around the corresponding rotating shaft in the range of 0° to 90°, for use in the level flight mode generate lift. Aerodynamic control surfaces are provided on the wing 2 to provide control of the aircraft in each mode. The wing 2 is provided with a rotating shaft hole, which can completely wrap the rotating shaft 3 in the wing.

There are two rotating shafts 3, which are fixed at the front and rear of the fuselage 1 respectively. They are used as the rotating shafts of the rotors 4 at both ends of the wing 2 and the wing 2, and bear the loads generated by them and transmit the loads to the fuselage. The rotating shaft 3 is hollow, and equipment such as wires can be arranged inside it.

The rotor 4 is arranged at the wingtips on both sides of the front and rear wings, that is, the ends of the front and rear two rotating shafts, a total of four groups, which constitute the power system of the aircraft, which is used to provide the power of the aircraft, using the speed differential belt between the four groups of rotors The incoming rotor power differential provides the control force. They can be rotated from 0° to 90° around the shaft on which they are installed, and the wires are passed through the hollow shaft to connect to the electronics inside the fuselage.

The electronic equipment 5 is arranged in the fuselage 1, including batteries, flight controllers, signal receivers, etc., for providing energy, controlling the attitude of the aircraft, receiving control commands, etc., to ensure that the aircraft can fly normally as designed.

A control method for a tilt-rotor-wing vertical take-off and landing aircraft, including control methods in the following four modes: vertical take-off and landing mode (as shown in Figure 3), vertical take-off and landing to level flight mode (as shown in Figure 4) (shown), level flight mode (as shown in Figure 5), and level flight to vertical take-off and landing mode (as shown in Figure 6).

The vertical take-off and landing mode is shown in FIG. 3 , the wing is in a vertical state, and the rotor is in a vertical state. The rotors now provide upward power, allowing the aircraft to climb vertically. Control is provided by differential rotor power.

Described vertical take-off and landing turns level flight mode as shown in Figure 4, wing is gradually turned into horizontal state by vertical state, and rotor is gradually turned into horizontal state by vertical state, and is divided into four steps in total:

Step 1: As shown in Figure 4a and Figure 4b, the wing first begins to gradually tilt to the horizontal state, the rotor does not move, and the power is used to offset the weight of the aircraft. At the same time, through the power differential of the front and rear rotors, the aircraft has a certain negative pitch angle, so that the power has a forward component, and the forward flight speed of the aircraft is improved. In this step, the rotor power differential is used to provide the control force of the aircraft;

Step 2: As shown in Figure 4b and Figure 4c, when the aircraft reaches a certain forward flight speed, the wing will tilt to a certain angle to ensure that the wing can provide greater lift, and the rotor begins to move horizontally Status tilted. This will increase the forward component of the rotor, so that the forward flight speed of the aircraft will be further improved, and the lift provided by the wing will also increase with the increase of the forward flight speed, offsetting the vertical direction reduced by the tilt of the rotor. power component. In this step, the rotor power differential is mainly used to provide control force, and the aerodynamic rudder surface can be used as an auxiliary;

Step 3: As shown in Figure 4c and Figure 4d, in order to ensure that the aircraft has a normal flight attitude in level flight, that is, the aircraft has a positive pitch angle, the wings and rotors will tilt synchronously until the wings are completely turned to the horizontal position , the pitch angle when the aircraft reaches normal level flight. At this point, when the forward flight speed reaches a certain value, the wing can already provide most of the lift, and the rotor does not need to provide a large vertical component to offset its own gravity. In this step, the rotor power differential is mainly used to provide control force, and the aerodynamic rudder surface can be used as an auxiliary;

Step 4: As shown in Figure 4d and Figure 4e, the rotor is completely turned to the horizontal state, only forward power is provided, and the aircraft enters the level flight mode. At this time, the wing can provide all the lift, which can completely offset the weight of the aircraft. In this step, the aerodynamic rudder surface is mainly used to provide the control force, and the rotor power differential can be used as an auxiliary.

The level flight mode is shown in FIG. 5 , and both the wing and the rotor are in a horizontal state. The rotor provides forward power, and the wings provide upward lift to offset the weight of the aircraft, allowing the aircraft to fly at high speed and level. The aircraft mainly provides the control force through the aerodynamic rudder surface arranged on the wing, and provides the yaw moment through the rotor power differential.

Described horizontal flight turns vertical take-off and landing mode as shown in Figure 6, the rotor gradually changes from the horizontal state to the vertical state, and the wing gradually changes from the horizontal state to the vertical state, which is divided into three steps:

The first step: As shown in Figure 6a, the rotor gradually tilts from the horizontal state to the vertical state, and the wing is in the horizontal state. At this time, the forward flight speed is still large, and the wings still provide most of the lift, which together with the vertical power component of the rotor offsets the weight of the aircraft. In this step, the aerodynamic rudder surface is mainly used to provide control force, and the rotor power differential can be used as an auxiliary;

Step 2: As shown in Figure 6b, the rotor is completely turned to the vertical state, and the wing is in the horizontal state. At this time, due to air resistance and other relations, the forward flight speed of the aircraft has dropped significantly, the wings can no longer provide enough lift, and the aerodynamic rudder surface is not enough to provide enough control. At this time, the rotor has been turned to a vertical state, and the power can be fully used to offset the weight of the aircraft. In this step, the rotor power differential is used to provide the control force;

Step 3: As shown in Figure 6c, the rotor is in a vertical state, and the wing is turned from a rapid horizontal state to a vertical state. In the previous step, although the forward flight speed has dropped significantly, it is still not 0. At this time, the lift provided by the wings is very small, and the aircraft no longer needs to rely on the wings to offset its own weight. At this time, the wings are quickly turned from the horizontal state to the vertical state, which can rapidly increase the forward windward area of the aircraft and act as a resistance plate, so that the forward flight speed is quickly reduced to 0, and the aircraft enters the vertical take-off and landing mode. And because the rotor can provide enough control at this time, it will not have an excessive impact on the flight attitude of the aircraft. In this step, the rotor power differential is used to provide the control force.

Claims (2)

1. The utility model provides a tiltrotor-wing VTOL aircraft's overall arrangement which characterized in that: the tiltrotor-wing VTOL aircraft includes: fuselage, wing, pivot, rotor, electronic equipment.

The fuselage is the main part of the aircraft and is used for bearing the payload and connecting other various parts of the aircraft;

the wings are divided into a front group and a rear group, are respectively connected with the fuselage through two rotating shafts arranged at the front and the rear of the fuselage, can rotate around the corresponding rotating shafts within the range of 0-90 degrees, and are used for generating lift force in a level flight mode. The wings are provided with pneumatic control surfaces for providing control force of the airplane. A rotating shaft hole is arranged in the wing, so that the rotating shaft can be completely wrapped in the wing;

the two rotating shafts are respectively fixed at the front part and the rear part of the fuselage and are used as rotating shafts of the wings at the two ends of the wings, so that the rotating shafts bear loads generated by the wings and transmit the loads to the fuselage. The rotating shaft is hollow, and equipment such as wires and the like can be arranged in the rotating shaft;

the rotary wings are arranged at wingtips at two sides of the front wing and the rear wing, namely the tail ends of the front rotating shaft and the rear rotating shaft, and the four rotary wings are combined to form a power system of the airplane, are used for providing power of the airplane, and provide control force by utilizing rotary wing power differential motion brought by rotation speed differential motion among the four groups of rotary wings. They can rotate in the range of 0 deg. to 90 deg. around the installed rotating shaft, and the electric wire is passed through the hollow rotating shaft and connected with electronic equipment in the interior of machine body;

the electronic equipment is arranged in the fuselage, comprises a battery, a flight control unit, a signal receiver and the like, and is used for providing energy, controlling the attitude of the airplane, receiving a control command and the like, and ensuring that the airplane can normally fly according to the design.

2. A method of controlling a tiltrotor-wing vtol aircraft according to claim 1, comprising: the method comprises the following four modes: the vertical take-off and landing mode, the vertical take-off and landing-to-flat flight mode, the flat flight mode and the flat flight-to-vertical take-off and landing mode. The specific control method comprises the following steps:

in the vertical take-off and landing mode, the wings are in a vertical state, and the rotors are in a vertical state. The rotor provides upward power to make the airplane climb vertically, and provides control force through rotor power differential.

The vertical take-off and landing rotating flying mode comprises four steps:

the first step is as follows: the wings begin to tilt gradually to the horizontal state, the rotor wing is fixed, and upward power is provided to offset the dead weight of the airplane. The aircraft has a certain negative pitch angle through the power differential of the front rotor and the rear rotor, so that the aircraft has forward power component, and the forward flying speed of the aircraft is improved. Providing control force of the airplane by using rotor power differential;

the second step is that: when the airplane has certain forward flying speed, the wings tilt to a certain angle to provide larger lift force, and at the moment, the rotor wing starts to tilt to the horizontal state, so that the forward power component of the rotor wing is improved, and the forward flying speed of the airplane is further improved. The lift provided by the wing will also increase with increasing forward flight speed, counteracting the vertical power component that is reduced by the rotor tilting. The power differential of the rotor wing is mainly utilized to provide control force, and a pneumatic control surface is used as assistance;

the third step: the wings and the rotor wings rotate synchronously until the wings rotate to the horizontal position completely, and the airplane reaches the pitch angle when the airplane flies normally. At the moment, the forward flying speed reaches a certain value, the wings can provide most of lift force, and the rotors are not required to provide larger vertical components to offset the self weight of the airplane. The power differential of the rotor wing is mainly utilized to provide control force, and a pneumatic control surface is used as assistance;

the fourth step: the rotor wing is completely turned to the horizontal state, only the forward power is provided, and the airplane enters a level flight mode. The lift provided by the wings can offset the self weight of the airplane. The aerodynamic control surface is mainly used for providing control force, and the dynamic differential of the rotor wing is used as assistance.

The horizontal flying mode, the wings and the rotor wings are all in a horizontal state. The rotor provides forward power and the lift provided by the wings counteracts the self weight of the aircraft. The control force is provided mainly through an aerodynamic control surface, and the yawing moment is provided through the dynamic differential of the rotor wing.

The horizontal flying rotation vertical take-off and landing mode is divided into three steps:

the first step is as follows: the rotor tilts gradually to vertical state by the horizontal state, and the wing is in the horizontal state. At the moment, the forward flying speed is high, the wings provide most of lift force, and the dead weight of the airplane is offset together with the vertical power component of the rotor wings. The aerodynamic control surface is mainly used for providing control force, and the dynamic differential of the rotor wing is used as assistance;

the second step is that: the rotor turns completely to the vertical state and the wing is in the horizontal state. At the moment, the front flying speed is low, the wing lifting force is low, and the self weight of the airplane is offset by using power. The control force is provided by using the power differential of the rotor wing;

the third step: the rotor wing is in vertical state, and the wing is turned into vertical state from the horizontal state fast, increases the forward windward area of aircraft rapidly, plays the effect of resistance board, lets preceding flying speed fast land to 0, and the aircraft gets into the vertical take-off and landing mode. The control force is provided by rotor power differential.

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