Wing lift
Wing lift
Author: Sinegubov Andrey
Group: E3-42
Artistic director: Sergey Burtsev
Alexeyevich

Formulation of the problem

Environment model

Airfoil

Reference surface

Calculation formulas

Zhukovsky's theorem

Wing lift

List of sources used

* An aircraft wing is designed to generate the lift needed to support the aircraft in the air. The aerodynamic quality of the wing is greater, the greater the lift and the less drag. The lift force and drag of the wing depend on the geometric characteristics of the wing. The geometric characteristics of the wing are reduced to the characteristics of the wing in plan and the characteristics

The wings of modern aircraft are elliptical in plan (a), rectangular (b), trapezoidal (c), swept (d) triangular (e)

The angle of the transverse V wing Geometric characteristics of the wing The shape of the wing in plan is characterized by span, area elongation, narrowing, sweep and transverse V Wingspan L is the distance between the ends of the wing in a straight line. The area of ​​the wing in terms of Skr is limited by the contours of the wing.

The area of ​​the trapezoidal and swept wings is calculated as the area of ​​two trapezoids where b 0 is the root chord, m; bk - end chord, m; - the average wing chord, m Wing extension is the ratio of the wing span to the average chord. If instead of bav we substitute its value from equality (2. 1), then the wing extension will be determined by the formula For modern supersonic and transonic aircraft, the wing extension does not exceed 2 - 5. For low-speed aircraft, the aspect ratio can reach 12-15, and for gliders up to 25.

Wing taper is the ratio of the axial chord to the end chord. For subsonic aircraft, the taper of the wing usually does not exceed 3, and for transonic and supersonic aircraft, it can vary widely. The sweep angle is the angle between the line of the leading edge of the wing and the transverse axis of the aircraft. Sweep can also be measured along the line of foci (passing 1/4 of the chord from the edge of attack) or along another line of the wing. For transonic aircraft, it reaches 45°, and for supersonic aircraft - up to 60°. The transverse angle V of the wing is the angle between the transverse axis of the aircraft and the lower surface of the wing. In modern aircraft, the transverse V angle ranges from +5° to -15°. The profile of a wing is the shape of its cross section. Profiles can be symmetrical or asymmetrical. Asymmetric, in turn, can be biconvex, plano-convex, concave-convex, etc. S-shaped. Lenticular and wedge-shaped can be used for supersonic aircraft. The main characteristics of the profile are: profile chord, relative thickness, relative curvature

Profile chord b is a straight line segment connecting the two most distant points of the profile Forms of wing profiles 1 - symmetrical; 2 - not symmetrical; 3 - plano-convex; 4 - biconvex; 5 - S-shaped; 6 - laminated; 7 - lenticular; 8 - diamond-shaped; 9 prominent

Geometric characteristics of the profile: b - profile chord; Cmax - maximum thickness; fmax - curvature arrow; x-coordinate of greatest thickness Angles of attack of the wing

The total aerodynamic force and the point of its application R is the total aerodynamic force; Y - lifting force; Q is the drag force; - attack angle; q - quality angle The relative profile thickness c is the ratio of the maximum thickness Сmax to the chord, expressed as a percentage:

The relative airfoil thickness c is the ratio of the maximum thickness Cmax to the chord, expressed as a percentage: The position of the maximum airfoil thickness Xc is expressed as a percentage of the chord length and is measured from the toe. For modern aircraft, the relative airfoil thickness is in the range of 416%. The relative profile curvature f is the ratio of the maximum curvature f to the chord, expressed as a percentage. The maximum distance from the center line of the profile to the chord determines the curvature of the profile. The middle line of the profile is drawn at an equal distance from the upper and lower contours of the profile. For symmetrical profiles, the relative curvature is equal to zero, while for asymmetric profiles this value is nonzero and does not exceed 4%.

AVERAGE AERODYNAMIC WING CHORD The average aerodynamic wing chord (MAC) is the chord of such a rectangular wing, which has the same area as the given wing, the magnitude of the total aerodynamic force and the position of the center of pressure (CP) at equal angles of attack

For a trapezoidal untwisted wing, the MAR is determined by geometric construction. To do this, the wing of the aircraft is drawn in plan (and on a certain scale). On the continuation of the root chord, a segment equal in size to the end chord is deposited, and on the continuation of the end chord (forward), a segment equal to the root chord is deposited. The ends of the segments are connected by a straight line. Then draw the middle line of the wing, connecting the straight middle of the root and end chords. The mean aerodynamic chord (MAC) will pass through the intersection point of these two lines.

Knowing the magnitude and position of the MAR on the aircraft and taking it as a baseline, determine relative to it the position of the center of gravity of the aircraft, the center of pressure of the wing, etc. The aerodynamic force of the aircraft is created by the wing and applied at the center of pressure. The center of pressure and the center of gravity, as a rule, do not coincide and therefore a moment of forces is formed. The value of this moment depends on the magnitude of the force and the distance between the CG and the center of pressure, the position of which is defined as the distance from the beginning of the MAR, expressed in linear terms or as a percentage of the length of the MAR.

WING Drag Drag is the resistance to the movement of an airplane's wing in the air. It consists of profile, inductive and wave resistance: Xcr=Xpr+Hind+XV. Wave drag will not be considered, as it occurs at flight speeds above 450 km/h. The profile resistance is made up of pressure and friction resistance: Хpr=ХД+Хtr. Pressure drag is the difference in pressure in front of and behind the wing. The greater this difference, the greater the pressure resistance. The pressure difference depends on the shape of the profile, its relative thickness and curvature, in the figure Cx is indicated - the coefficient of profile resistance).

The greater the relative thickness c of the airfoil, the more the pressure rises in front of the wing and the more it decreases behind the wing, at its trailing edge. As a result, the pressure difference increases and, consequently, the pressure resistance increases. When an air flow flows around the wing profile at angles of attack close to critical, the pressure resistance increases significantly. At the same time, the dimensions of the swirling wake jet and the vortices themselves increase sharply. The magnitude of friction forces depends on the structure of the boundary layer and the state of the streamlined surface of the wing (its roughness). In a laminar boundary layer of air, friction resistance is less than in a turbulent boundary layer. Consequently, the greater part of the wing surface flows around the laminar boundary layer of the air flow, the lower the friction resistance. The value of friction resistance is affected by: aircraft speed; surface roughness; wing shape. The higher the flight speed, the wing surface is processed with worse quality and the wing profile is thicker, the greater the friction resistance.

Inductive drag is an increase in drag associated with the formation of wing lift. When an undisturbed air flow flows around a wing, a pressure difference arises above and below the wing. As a result, part of the air at the ends of the wings flows from a zone of higher pressure to a zone of lower pressure

The angle at which the flow of air flowing around the wing with a speed V induced by a vertical speed U is deflected is called the skew angle of the flow. Its value depends on the value of the vertical velocity induced by the vortex bundle and the oncoming flow velocity V

Therefore, due to the bevel of the flow, the true angle of attack of the east of the wing in each of its sections will differ from the geometric or apparent angle of attack each by an amount. As is known, the lift force of the wing ^ Y is always perpendicular to the oncoming flow, its direction. Therefore, the lift vector of the wing deviates by an angle and is perpendicular to the direction of the air flow V. lifting force there will be not the whole force ^ Y "but its component Y, directed perpendicular to the oncoming flow

In view of the smallness of the value, we consider equal to Another component of the force Y "will be This component is directed along the flow and is called inductive drag (Fig. presented above). To find the value of inductive drag, it is necessary to calculate the speed ^ U and the flow angle. Dependence of the flow angle on the aspect ratio of the wing , the coefficient of lift Su and the shape of the wing in plan is expressed by the formula in terms of.

where Cxi is the coefficient of inductive resistance. It is determined by the formula It can be seen from the formula that Cx is directly proportional to the lift coefficient and inversely proportional to the aspect ratio of the wing. At an angle of attack of zero lift o, the inductive reactance will be zero. At supercritical angles of attack, the smooth flow around the wing profile is disturbed and, therefore, the formula for determining Cx 1 is not acceptable for determining its value. Since the value of Cx is inversely proportional to the aspect ratio of the wing, therefore, aircraft intended for flights over long distances have a large aspect ratio of the wing: = 14 ... 15.

WING aerodynamic quality The aerodynamic quality of a wing is the ratio of the lift force to the drag force of the wing at a given angle of attack where Y is the lift force, kg; Q - drag force, kg. Substituting the values ​​of Y and Q into the formula, we get The greater the aerodynamic quality of the wing, the more perfect it is. The value of quality for modern aircraft can reach 14-15, and for gliders 45-50. This means that the wing of an aircraft can create lift that is 14 to 15 times the drag, and for gliders even 50 times.

The lift-to-drag ratio is characterized by the angle The angle between the vectors of lift and total aerodynamic forces is called the lift-to-drag angle. The greater the lift-to-drag ratio, the smaller the lift angle, and vice versa. The aerodynamic quality of the wing, as can be seen from the formula, depends on the same factors as the coefficients Cy and Cx, i.e., on the angle of attack, airfoil shape, wing shape in plan, flight M number and surface treatment. INFLUENCE ON THE ANGLE OF ATTACK QUALITY With an increase in the angle of attack to a certain value, the aerodynamic quality increases. At a certain angle of attack, the quality reaches its maximum value Kmax. This angle is called the most advantageous angle of attack, naive. equals zero. The effect on the lift-to-drag ratio of the airfoil shape is related to the relative thickness and curvature of the airfoil. In this case, the shape of the contours of the profile, the shape of the toe and the position of the maximum thickness of the profile along the chord have a great influence. To obtain large values Kmax, the optimal thickness and curvature of the profile, the shape of the contours and the elongation of the wing are selected. To obtain the highest quality values, the best wing shape is elliptical with a rounded leading edge.

Graph of the dependence of the aerodynamic quality on the angle of attack Formation of suction force Dependence of the aerodynamic quality on the angle of attack and airfoil thickness Change in the aerodynamic quality of the wing depending on the M number

WING POLAR For various calculations of the flight characteristics of a wing, it is especially important to know the simultaneous change in Cy and Cx in the range of flight angles of attack. For this purpose, a graph of the dependence of the coefficient Su on Cx is constructed, called the polar. The name “polar” is explained by the fact that this curve can be considered as a polar diagram built on the coordinates of the coefficient of the total aerodynamic force CR and, where is the angle of inclination of the total aerodynamic force R to the direction of the oncoming flow velocity (provided that the scales Su and Cx are taken to be the same ). The principle of construction of the wing polar Wing polar If from the origin, aligned with the airfoil pressure center, a vector is drawn to any point on the polar, then it will be a diagonal of a rectangle, the sides of which are respectively equal to Сy and Сх. drag and lift coefficient from angles of attack - the so-called wing polar.

The polar is constructed for a well-defined wing with given geometric dimensions and profile shape. A number of characteristic angles of attack can be determined from the wing polar. The zero-lift angle o is located at the intersection of the polar with the Cx axis. At this angle of attack, the lift coefficient is zero (Сy = 0). For the wings of modern aircraft, usually o = Angle of attack at which Cx has the smallest Cx value. min. is found by drawing a tangent to the polar parallel to the Cy axis. For modern wing profiles, this angle is in the range from 0 to 1°. The most advantageous angle of attack is naive. Since at the most favorable angle of attack the aerodynamic quality of the wing is maximum, the angle between the axis Сy and the tangent drawn from the origin, i.e. the quality angle, at this angle of attack, according to formula (2. 19), will be minimal. Therefore, to determine the naive, it is necessary to draw a tangent to the polar from the origin. The touch point will match the naive. For modern wings, naive lies in the range of 4 - 6 °.

Critical angle of attack crit. To determine the critical angle of attack, it is necessary to draw a tangent to the polar parallel to the Cx axis. The touch point and will correspond to crit. For the wings of modern aircraft, crit = 16 -30°. The angles of attack with the same lift-to-drag ratio are found by drawing a secant from the origin to the polar. At the intersection points, we find the angles of attack (u) during flight, at which the lift-to-drag ratio will be the same and necessarily less than Kmax.

AIRCRAFT POLAR One of the main aerodynamic characteristics of an aircraft is the aircraft polar. The lift coefficient of the wing Cy is equal to the lift coefficient of the entire aircraft, and the drag coefficient of the aircraft for each angle of attack is greater than Cx of the wing by the value of Cxvr. In this case, the aircraft polar will be shifted to the right of the wing polar by Cx temp. The aircraft polar is built using the data of the dependences Сy=f() and Сх=f(), obtained experimentally by blowing models in wind tunnels. The angles of attack on the aircraft's polar are affixed by horizontally transferring the angles of attack marked on the wing's polar. The determination of aerodynamic characteristics and characteristic angles of attack along the aircraft polar is carried out in the same way as it was done on the wing polar.

The zero-lift angle of attack of an aircraft is practically the same as the zero-lift angle of attack of a wing. Since the lift force is zero at the angle, at this angle of attack only vertical downward movement of the aircraft, called a vertical dive, or a vertical slide at an angle of 90 ° is possible.

The angle of attack at which the drag coefficient has a minimum value is found by drawing a tangent to the polar parallel to the Cy axis. When flying at this angle of attack, there will be least loss for resistance. At this angle of attack (or close to it), the flight is performed at maximum speed. The most favorable angle of attack (naive) corresponds to the highest value of the aerodynamic quality of the aircraft. Graphically, this angle, as well as for the wing, is determined by drawing a tangent to the polar from the origin. It can be seen from the graph that the slope of the tangent to the aircraft polar is greater than that of the tangent to the wing polar. Conclusion: the maximum quality of the aircraft as a whole is always less than the maximum aerodynamic quality of a single wing.

It can be seen from the graph that the most advantageous angle of attack of the aircraft is greater than the most advantageous angle of attack of the wing by 2 - 3°. The critical angle of attack of an aircraft (crit) does not differ in its value from the value of the same angle for the wing. The extension of the flaps to the takeoff position (= 15 -25°) allows you to increase the maximum lift coefficient Sumax with a relatively small increase in the drag coefficient. This makes it possible to reduce the required minimum flight speed, which practically determines the takeoff speed of the aircraft during takeoff. Due to the release of the flaps (or flaps) in the takeoff position, the takeoff run is reduced by up to 25%.

When the flaps (or flaps) are extended to the landing position (= 45 - 60°), the maximum lift coefficient can increase up to 80%, which drastically reduces the landing speed and the length of the run. However, the drag in this case increases more intensively than the lifting force, so the aerodynamic quality is significantly reduced. But this circumstance is used as a positive operational factor - the steepness of the trajectory increases during gliding before landing and, consequently, the aircraft becomes less demanding on the quality of approaches in the alignment of the runway. However, when such M numbers are reached at which compressibility can no longer be neglected (M > 0.6 - 0.7), the lift and drag coefficients must be determined taking into account the correction for compressibility. where Suszh is the lift coefficient taking into account compressibility; Suneszh is the lift coefficient of an incompressible flow for the same angle of attack as Suszh.

Up to the numbers M = 0.6 -0.7, all the polars practically coincide, but at large numbers ^ M they begin to shift to the right and simultaneously increase the slope to the Cx axis. The displacement of the polars to the right (by large Cx) is due to an increase in the profile resistance coefficient due to the influence of air compressibility, and with a further increase in the number (M > 0.75 - 0.8) due to the appearance of wave resistance. An increase in the tilt of the polars is explained by an increase in the coefficient of inductive drag, since at the same angle of attack in a subsonic flow of compressible gas, the lift-to-drag ratio of the aircraft begins to decrease from the moment the effect of compressibility is noticeable.

Why do birds fly? What forces lift the plane? Why does a glider float in the air? Hypothesis: the aircraft will take off if the necessary conditions are created. Purpose of the study: to get acquainted with the theory of flight; identify the conditions necessary for the flight of an aircraft. Research objectives: To determine the conditions necessary for the emergence of the lift force of the wing; Determine the conditions that ensure the stability of the aircraft. Methods and methods of research Analysis of the literature on the problem, Experimental work to identify the conditions for the flight of an aircraft (determination of the center of gravity and flight range, the influence of the position of the center of gravity, propeller and wing shape on the flight range). Analysis of the results of experimental work Studied the Three principles of creating a lifting force, Archimedes' law, Bernoulli's law. Learned Why and how there is a lifting force? (angle of attack, center of pressure of the wing) On flight stability, center of gravity, value of centering of the model for setting rectilinear motion (displacement of the center of gravity). Why and how an airplane flies. flight modes. 1. Three principles of creating lift force Aerostatic Aerodynamic Rocket Law of Archimedes The aerostatic principle of creating lift force can be explained using the Archimedes law, which is equally valid for both liquid and air environments: “The force pushing out a body completely immersed in a liquid or gas, equal to the weight of the liquid or gas in the volume of this body. Aircraft based on the aerostatic principle are called balloons or aerostats. Bernoulli's law The aerodynamic principle is explained by Bernoulli's law. creation If the speed of air flow around the upper edge of the wing is greater than the lower one. The air pressure on the bottom edge is greater than on the top. p2+1/2ρv 22 =p1 +1/2 ρv 21, ∆p=p2-p1=1/2 ρ(v21-v22). The lifting force of gliders, airplanes, helicopters is created according to the aerodynamic principle. 2. Why and how the lift force arises Nikolai Yegorovich Zhukovsky Y- Lift force of the wing, R - aerodynamic force, X - drag force, CP - center of pressure of the wing 3. How flight stability is ensured Varieties of propellers and their application air screw. Jet engines turbojet turboprop 4. Aircraft flight modes Y-wing lift force, R- aerodynamic force, X- drag force, P-propeller thrust Let the aircraft fly straight along a horizontal trajectory with some constant air force R. Let's decompose this force into two - perpendicular to the direction of flight Y and along the flight X. The aircraft is affected by gravity G. Forces Y and G must be equal in magnitude, otherwise the aircraft will not fly horizontally. The propeller thrust force P acts on the aircraft, which is directed in the direction of the aircraft's movement. This force balances the drag force. So, in steady horizontal flight, the wing lift is equal to the aircraft's gravity, and the propeller thrust is equal to the drag. In the absence of equality of these forces, the movement is called curvilinear. P - propeller thrust force, Y - wing lift force, R - aerodynamic force, X - drag force, G, G1, G2 - gravity forces. Let us now consider what forces act on the aircraft during a steady rise. The lifting force Y is directed perpendicular to the movement of the aircraft, the drag force X is directly against the movement, the thrust force P is along the movement and the gravity force G is vertically downward. Y-Lift force of the wing, R-aerodynamic force, X-force of drag G,G1,G2-gravity. Gliding is characterized by continuous loss of altitude. The force R must balance the force G. Due to the action of the force G 2, which balances the drag X, and the possible gliding of the aircraft. Analysis of the results of the study The conditions necessary for the flight were studied and tested on models. Journal of research Main indicators of models Length, cm Time, s Speed, m/s Model 180 0.56 3.21 Foam glider 180 0.94 1.91 Foam rubber motor 180 0.59 3.05 Paper glider 180 0.63 2, 85 Hummingbird glider 180 0.90 2.00 Rubber motor characteristics of my models model + Rubber motor The propeller, wing shape, wing dimensions, ribs on the stabilizer, removable all parts Small size - less drag Propeller "Ears" (stability in flight) Durable Rubber motor weight Screw-resistance in planning Strength, lightness, the presence of a screw - Hummingbird Glider Foam rubber motorka Foam plastic glider Electrolet - Weight - heavy weight, no ribs on the stabilizer, non-removable parts Fragility, weight of the rubber motor, spacer mast (drag resistance) Weight – heavy weight Dependence of the rubber motor torque value on the length and cross section of the bundle length, cm Bundle cross section, cm² Torque, kg/cm 30 0.24* 0.100 40 0.40 0.215 45 0.56 0.35 6 50 0.64 0.433 55 0.80* 0.800 Model wing lift Model Model wing lift Rubber motor 0.21 N Hummingbird glider 0.48 N Foam glider 0.21 N Foam rubber motor. 0.07 N RESULTS OF EXPERIMENTS 1. Each class has its own model is strong; 2. You can not compare different classes of models with each other. 3. You can compare: rubber motors with the same rubber motor weight; cord with the same engine size; gliders are the same size. Conclusions on the work: Thus, having studied the material on the theory of flight, the principles and causes of the emergence of lift, I concluded that in order for the aircraft to fly, the following conditions are necessary: ​​Correct wing centering; Sufficient propeller thrust; The correct location of the center of gravity of the aircraft; In the process of research, my hypothesis about the need for certain conditions for the flight of an aircraft turned out to be correct. Bibliography 1. 2. 3. 4. 5. 6. Ermakov A.M. The simplest aircraft models. Moscow, Enlightenment, 1984 Gaevsky O.K. Aeromodelling. Moscow, Enlightenment, 1964 Duz P.D. History of aeronautics and aviation in the USSR. Moscow, Enlightenment, 1960 Internet sites Anoshchenko N.D. Balloonists. Moscow, Education, 2004 Children's Encyclopedia. Technics. Moscow, Avanta +, 2007

Consider now the flow of air around the wing of an aircraft. Experience shows that when a wing is placed in a stream of air, vortices appear near the sharp trailing edge of the wing, rotating in the case shown in Fig. 345 counterclockwise. These vortices grow, break away from the wing and are carried away by the flow. The rest of the air mass near the wing receives in this case the opposite rotation (clockwise), forming a circulation near the wing (Fig. 346). Superimposed on the total flow, the circulation determines the distribution of streamlines shown in Fig. 347.

Rice. 345. A vortex forms at the sharp edge of the wing profile

Rice. 346. When a vortex is formed, air circulation around the wing occurs

Rice. 347. The vortex is carried away by the flow, and the streamlines smoothly flow around the profile; they are condensed above the wing and sparse under the wing

We obtained the same flow pattern for the wing profile as for a rotating cylinder. And here the rotation around the wing is superimposed on the general air flow - circulation. Only, in contrast to a rotating cylinder, here the circulation occurs not as a result of the rotation of the body, but due to the appearance of vortices near the sharp edge of the wing. Circulation speeds up the movement of air above the wing and slows it down under the wing. As a result, the pressure above the wing decreases, and under the wing it increases. The resultant of all forces acting from the side of the flow on the wing (including friction forces) is directed upward and slightly deflected back (Fig. 341). Its component perpendicular to the flow is the lift force, and the component in the direction of the flow is the drag force. The greater the speed of the oncoming flow, the greater both the lift force and the drag force. These forces also depend on the shape of the wing profile, and on the angle at which the flow runs onto the wing (angle of attack), as well as on the density of the oncoming flow: the greater the density, the greater these forces. The profile of the wing is chosen so that it gives as much lift as possible with as little drag as possible. The theory of the emergence of the lift force of the wing when flowing around the air flow was given by the founder of the theory of aviation, the founder of the Russian school of aero - and hydrodynamics, Nikolai Yegorovich Zhukovsky (1847-1921).

Now we can explain how an airplane flies. The propeller of an aircraft, rotated by the engine, or the reaction of the jet engine, imparts to the aircraft such a speed that the lift force of the wing reaches the weight of the aircraft and even exceeds it. Then the plane takes off. In uniform rectilinear flight, the sum of all forces acting on the aircraft is zero, as it should be according to Newton's first law. On fig. 348 shows the forces acting on an aircraft in level flight at a constant speed. The thrust force of the engine is equal in magnitude and opposite in direction to the force of air drag for the entire aircraft, and the force of gravity is equal in magnitude and opposite in direction to the lift force.

Rice. 348. Forces acting on an aircraft during horizontal uniform flight

Aircraft designed to fly at different speeds have different wing sizes. Slowly flying transport aircraft must have a large wing area, since at low speed the lift per unit wing area is small. High-speed aircraft also receive sufficient lift from wings of a small area. Since wing lift decreases as air density decreases, to fly at high altitude an aircraft must move at a higher speed than near the ground.

Lift also occurs when the wing moves through the water. This makes it possible to build ships moving on hydrofoils. The hull of such vessels emerges from the water during movement (Fig. 349). This reduces the resistance of the water to the movement of the vessel and allows you to achieve a high speed. Since the density of water is many times greater than the density of air, it is possible to obtain sufficient lift from a hydrofoil with a relatively small area and moderate speed.

Rice. 349. Hydrofoil

The purpose of an aircraft propeller is to give the aircraft a high speed, at which the wing creates a lifting force that balances the weight of the aircraft. For this purpose, the propeller of the aircraft is fixed on a horizontal axis. There is a type aircraft heavier than air, for which wings are not needed. These are helicopters (Fig. 350).

Rice. 350. Helicopter scheme

In helicopters, the propeller axis is vertical and the propeller creates upward thrust, which balances the weight of the helicopter, replacing the lift of the wing. The helicopter propeller creates vertical thrust whether the helicopter is moving or not. Therefore, when the propellers are operating, the helicopter can hang motionless in the air or rise vertically. For horizontal movement of the helicopter, it is necessary to create thrust directed horizontally. To do this, it is not necessary to install a special propeller with a horizontal axis, but it is enough to slightly change the inclination of the vertical propeller blades, which is performed using a special mechanism in the propeller hub.