velocity of flow slant behind the wing vertically in m/sec. In the same way, it is possible to express the total aerodynamic force of a helicopter's main rotor in terms of the second air flow rate and the flow shear velocity (the inductive speed of the outgoing air stream).

The rotating rotor sweeps away a surface that can be thought of as a load-bearing surface, similar to an airplane wing (Fig. 8). Air flowing through the surface swept by the rotor is, as a result of interaction with the rotating blades, thrown down at an inductive speed And. In the case of horizontal or inclined flight, air flows to the surface, swept by the main rotor at a certain angle (oblique blowing). Like an airplane, the volume of air involved in creating the total aerodynamic force of the main rotor can be represented as a cylinder, the base area of ​​which is equal to the surface area swept by the main rotor, and the length equals the flight speed, expressed in m/sec.

Coursework on design

Light helicopter

1 Development of tactical and technical requirements. 2

2 Calculation of helicopter parameters. 6

2.1 Calculation of payload mass. 6

2.2 Calculation of helicopter rotor parameters. 6

2.3 Relative air densities on static and dynamic ceilings 8

2.4 Calculation of economic speed at the ground and on the dynamic ceiling. 8

2.5 Calculation of the relative values ​​of the maximum and economic speeds of horizontal flight on a dynamic ceiling. 10

2.6 Calculation of permissible ratios of thrust coefficient to rotor filling for maximum speed near the ground and for economic speed on a dynamic ceiling. 10

2.7 Calculation of rotor thrust coefficients at the ground and on the dynamic ceiling 11

2.8 Calculation of rotor filling. 12

2.9 Determination of the relative increase in main rotor thrust to compensate for the aerodynamic drag of the fuselage and horizontal tail. 13

3 Calculation of the power of the helicopter propulsion system. 13

3.1 Calculation of power when hanging on a static ceiling. 13

3.2 Calculation of power density in level flight at maximum speed. 14

3.3 Calculation of specific power in flight on a dynamic ceiling at economic speed.. 15

3.4 Calculation of specific power in flight near the ground at economic speed in the event of failure of one engine during takeoff. 15

3.5 Calculation of specific reduced powers for various flight cases 16

3.5.1 Calculation of specific reduced power when hanging on a static ceiling 16

3.5.2 Calculation of specific reduced power in horizontal flight at maximum speed. 16

3.5.3 Calculation of specific reduced power in flight on a dynamic ceiling at economic speed... 17

3.5.4 Calculation of specific reduced power in flight near the ground at economic speed in case of failure of one engine. 18

3.5.5 Calculation of the required power of the propulsion system. 19

3.6 Selection of engines. 19

4 Calculation of fuel mass. 20

4.1 Calculation of cruising speed of the second approximation. 20

4.2 Calculation of specific fuel consumption. 22

4.3 Calculation of fuel mass. 23

5 Determination of the mass of helicopter components and assemblies. 24

5.1 Calculation of the mass of the main rotor blades. 24

5.2 Calculation of the mass of the main rotor hub. 24

5.3 Calculation of the mass of the booster control system. 25

5.4 Calculation of the mass of the manual control system. 25

5.5 Calculation of the mass of the main gearbox. 26

5.6 Calculation of the mass of the tail rotor drive units. 27

5.7 Calculation of the mass and main dimensions of the tail rotor. thirty

5.8 Calculation of the mass of the helicopter propulsion system. 32

5.9 Calculation of the mass of the fuselage and helicopter equipment. 32

5.10 Calculation of helicopter take-off weight of the second approximation. 35

6 Description of the helicopter layout. 36

References.. 39

1 Development of tactical and technical requirements

The projected object is a light single-rotor helicopter with a maximum take-off weight of 3500 kg. We select 3 prototypes so that their maximum take-off weight is in the range of 2800-4375 kg. The prototypes are light helicopters: Mi-2, Eurocopter EC 145, Ansat.

Table 1.1 shows their tactical and technical characteristics necessary for the calculation.

Table 1.1 - Performance characteristics of prototypes

Figures 1.1, 1.2 and 1.3 show schematics of the prototypes.

Figure 1.1 - Diagram of the Mi-2 helicopter

Figure 1.2 - Diagram of the Eurocopter EC 145 helicopter

Figure 1.3 - Ansat helicopter diagram

From tactical and technical characteristics and prototype diagrams, we determine the average values ​​​​of the quantities and obtain the initial data for designing the helicopter.

Table 1.2 - Initial data for helicopter design

2 Calculation of helicopter parameters

2.1 Calculation of payload mass

Formula (2.1.1) for determining the payload mass:

Where m mg - payload mass, kg; m ek - crew mass, kg; L- flight range, km; m 01 - maximum take-off weight of the helicopter, kg.

Payload weight:

2.2 Calculation of helicopter rotor parameters

Radius R, m, of the main rotor of a single-rotor helicopter is calculated using formula (2.2.1):

, (2.2.1)

Where m 01 - helicopter take-off weight, kg; g- free fall acceleration equal to 9.81 m/s 2 ; p- specific load on the area swept by the main rotor, p = 3.14.

We take the radius of the rotor equal to R= 7.2 m.

Determine the value of the peripheral speed wR the ends of the blades from the diagram shown in Figure 3:

Figure 3 - Diagram of the dependence of the tip speed of the blade on the flight speed for constant values M 90 and μ

At Vmax= 258 km/h wR = 220 m/s.

Determining the angular velocity w, s -1 , and rotor rotation frequency according to formulas (2.2.2) and (2.2.3):

2.3 Relative air densities on static and dynamic ceilings

The relative air densities on static and dynamic ceilings are determined by formulas (2.3.1) and (2.3.2), respectively:

2.4 Calculation of economic speed at the ground and on a dynamic ceiling

The relative area is determined S e equivalent harmful plate according to formula (2.4.1):

Where S E is determined according to Figure 4.

Figure 4 - Change in the area of ​​the equivalent harmful plate of various transport helicopters

We accept S E = 1.5

The value of economic speed near the ground is calculated V h, km/h:

Where I- induction coefficient:

I =1,02+0,0004Vmax = 1,02+0,0004258=1,1232 ,

The value of the economic speed on the dynamic ceiling is calculated V din, km/h:

2.5 Calculation of the relative values ​​of the maximum and economic speeds of horizontal flight on a dynamic ceiling

Calculation of the relative values ​​of the maximum and economic speeds of horizontal flight on a dynamic ceiling is carried out using formulas (2.5.1) and (2.5.2), respectively:

; (2.5.1)

. (2.5.2)

2.6 Calculation of permissible ratios of thrust coefficient to rotor filling for maximum speed at the ground and for economic speed at the dynamic ceiling

Since formula (2.6.1) for the ratio of the permissible thrust coefficient to the rotor filling for maximum ground speed has the form:

Formula (2.6.2) for the ratio of the permissible thrust coefficient to the rotor filling for economic speed on a dynamic ceiling:

2.7 Calculation of rotor thrust coefficients at the ground and on the dynamic ceiling

Calculation of the rotor thrust coefficients at the ground and on the dynamic ceiling is carried out using formulas (2.7.1) and (2.7.2), respectively:

2.8 Calculation of rotor filling

Main rotor filling s calculated for cases of flight at maximum and economic speeds:

As a calculated fill value s main rotor, the value from condition (2.8.3) is taken:

we accept.

Chord length b and relative elongation l rotor blades will be equal to:

2.9 Determination of the relative increase in main rotor thrust to compensate for the aerodynamic drag of the fuselage and horizontal tail

We accept a relative increase in main rotor thrust to compensate for the aerodynamic drag of the fuselage and horizontal tail.

3 Calculation of the power of a helicopter propulsion system

3.1 Calculation of power when hanging on a static ceiling

The specific power required to drive the main rotor in hover mode on a statistical ceiling is calculated using formula (3.1.1)

Where NH st - required power, W;

Throttle characteristic, which depends on the height of the static ceiling and is calculated using formula (3.1.2)

m 0 - take-off weight, kg;

g- free fall acceleration, m/s 2 ;

p- specific load on the area swept by the main rotor, N/m 2 ;

D st - relative air density at the height of the static ceiling;

h 0 - relative efficiency main rotor in hover mode ( h 0 =0.75);

Relative increase in main rotor thrust to balance the aerodynamic drag of the fuselage:

3.2 Calculation of power density in level flight at maximum speed

The specific power required to drive the main rotor in horizontal flight at maximum speed is calculated using formula (3.2.1)

where is the peripheral speed of the ends of the blades;

Relative equivalent harmful plate;

Induction coefficient determined by formula (3.2.2)

3.3 Calculation of power density in flight on a dynamic ceiling at economic speed

The specific power for driving a main rotor on a dynamic ceiling is:

where is the relative density of air on the dynamic ceiling;

Economic speed of a helicopter on a dynamic ceiling;

3.4 Calculation of specific power in flight near the ground at economic speed in the event of one engine failure during takeoff

The specific power required to continue takeoff at economic speed in the event of one engine failure is calculated using formula (3.4.1)

where is the economic speed at the ground;

3.5 Calculation of specific reduced powers for various flight cases

3.5.1 Calculation of specific reduced power when hanging on a static ceiling

Calculation of specific reduced power when hanging on a static ceiling is carried out according to formula (3.5.1.1)

where is the specific throttle characteristic:

x 0 - power utilization factor of the propulsion system in hover mode. Since the weight of the designed helicopter is 3.5 tons, ;

3.5.2 Calculation of specific reduced power in level flight at maximum speed

Calculation of specific reduced power in horizontal flight at maximum speed is carried out according to formula (3.5.2.1)

where is the power utilization factor at maximum flight speed,

Engine throttle characteristics depending on flight speed:

3.5.3 Calculation of specific reduced power in flight on a dynamic ceiling at economic speed

Calculation of specific reduced power in flight on a dynamic ceiling at economic speed is carried out according to formula (3.5.3.1)

where is the power utilization factor at economic flight speed,

and - degrees of engine throttling, depending on the height of the dynamic ceiling H and flight speed V din in accordance with the following throttle characteristics:

3.5.4 Calculation of specific reduced power in flight near the ground at economic speed when one engine fails

Calculation of specific reduced power in flight near the ground at economic speed in case of failure of one engine is carried out according to the formula (3.5.4.1)

where is the power utilization factor at economic flight speed;

The degree of engine throttling in emergency mode;

Number of helicopter engines;

The degree of engine throttling when flying near the ground at economic speed:

3.5.5 Calculation of the required power of the propulsion system

To calculate the required power of the propulsion system, the value of the specific reduced power is selected from condition (3.5.5.1)

Required power N helicopter propulsion system will be equal to:

where is the take-off weight of the helicopter;

g= 9.81 m 2 /s - free fall acceleration;

3.6 Selection of engines

We accept two gas turbine engine GTD-1000T with a total power of 2×735.51 kW. The condition is met.

4 Calculation of fuel mass

4.1 Second approximation cruising speed calculation

We accept the value of the first approach cruising speed.

Since we calculate the induction coefficient using formula (4.1.1):

We determine the specific power required to drive the main rotor in flight at cruising mode using formula (4.1.2):

where is the maximum value of the specific reduced power of the propulsion system,

Power change coefficient depending on flight speed, calculated by the formula:

We calculate the cruising speed of the second approach:

We determine the relative deviation of the cruising speeds of the first and second approximations:

Since we are refining the cruising speed of the first approximation, it is taken to be equal to the calculated speed of the second approximation. Then we repeat the calculation using formulas (4.1.1) - (4.1.5):

We accept.

4.2 Calculation of specific fuel consumption

Specific fuel consumption is calculated using formula (4.2.1):

where is the coefficient of change in specific fuel consumption depending on the operating mode of the engines,

The coefficient of change in specific fuel consumption depending on flight speed, which is determined by formula (4.2.2):

Specific fuel consumption at takeoff, ;

Coefficient of change in specific fuel consumption depending on temperature,

Coefficient of change in specific fuel consumption depending on flight altitude, ;

4.3 Calculation of fuel mass

The mass of fuel spent on the flight will be equal to:

, (4.3.1)

where is the specific power consumed at cruising speed;

Cruising speed;

Specific fuel consumption;

L- range of flight;

5 Determination of the mass of helicopter components and assemblies

5.1 Calculation of the mass of the main rotor blades

The mass of the main rotor blades is determined by formula (5.1.1):

Where R- radius of the main rotor;

s- filling the main rotor;

5.2 Calculation of rotor hub mass

The mass of the main rotor hub is calculated using formula (5.2.1):

where is the weight coefficient of bushings of modern designs, ;

The coefficient of influence of the number of blades on the mass of the hub, which is calculated by formula (5.2.2):

Centrifugal force acting on the blades, which is calculated by formula (5.2.3):

5.3 Calculation of the mass of the booster control system

The booster control system includes a swashplate, hydraulic boosters, and a hydraulic main rotor control system. The mass of the booster control system is calculated using formula (5.3.1):

Where b- chord of the blade;

The weight coefficient of the booster control system, which can be taken equal to 13.2 kg/m 3 ;

5.4 Calculation of the mass of the manual control system

Calculation of the mass of the manual control system is carried out according to formula (5.4.1):

where is the weight coefficient of the manual control system, taken for single-rotor helicopters to be equal to 25 kg/m;

5.5 Calculation of the mass of the main gearbox

The mass of the main gearbox depends on the torque on the main rotor shaft and is calculated using formula (5.5.1):

where is the weight coefficient, the average value of which is 0.0748 kg/(Nm) 0.8.

The maximum torque on the main rotor shaft is determined through the reduced power of the propulsion system N and propeller speed w:

where is the power utilization factor of the propulsion system, the value of which is taken depending on the take-off weight of the helicopter. Since, then;

5.6 Calculation of the mass of the tail rotor drive units

The tail rotor thrust is calculated:

where is the torque on the main rotor shaft;

The distance between the axes of the main and tail rotors.

Distance L between the axes of the main and tail rotors is equal to the sum of their radii and clearance d between the ends of their blades:

where is the gap, taken equal to 0.15...0.2 m;

Tail rotor radius. Since then

The power consumed to rotate the tail rotor is calculated using formula (5.6.3):

where is the relative efficiency of the tail rotor, which can be taken equal to 0.6...0.65.

The torque transmitted by the steering shaft is equal to:

where is the steering shaft rotation speed, which is found according to formula (5.6.5):

The torque transmitted by the transmission shaft at rpm is equal to:

Weight m in transmission shaft:

where is the weight coefficient for the transmission shaft, which is equal to 0.0318 kg/(Nm) 0.67;

The mass of the intermediate gearbox is determined by formula (5.6.9):

where is the weight coefficient for the intermediate gearbox, equal to 0.137 kg/(Nm) 0.8.

Mass of the tail gearbox rotating the tail rotor:

where is the weight coefficient for the tail gearbox, the value of which is 0.105 kg/(Nm) 0.8;

5.7 Calculation of the mass and main dimensions of the tail rotor

The mass and main dimensions of the tail rotor are calculated depending on its thrust.

The tail rotor thrust coefficient is:

The filling of the tail rotor blades is calculated in the same way as for the main rotor:

where is the permissible value of the ratio of the thrust coefficient to the tail rotor filling,

The chord length and relative elongation of the tail rotor blades are calculated using formulas (5.7.3) and (5.7.4):

where is the number of main rotor blades,

The mass of the tail rotor blades is calculated using the empirical formula (5.7.5):

The value of the centrifugal force acting on the tail rotor blades and perceived by the hub hinges is calculated using the formula (5.7.6):

The mass of the tail rotor hub is calculated using the same formula as for the main rotor:

where is the centrifugal force acting on the tail rotor blade;

The weight coefficient for the bushing, which is equal to 0.0527 kg/kN 1.35;

Weight coefficient depending on the number of blades and calculated according to formula (5.7.8):

5.8 Calculation of the mass of the helicopter propulsion system

The specific mass of a helicopter propulsion system is calculated using the empirical formula (5.8.1):

, (5.8.1)

Where N- power of the propulsion system;

The mass of the propulsion system will be equal to:

5.9 Calculation of the weight of the fuselage and helicopter equipment

The mass of the helicopter fuselage is calculated using formula (5.9.1):

where is the area of ​​the washed surface of the fuselage:

Table 5.8.1

First approximation take-off weight;

Coefficient equal to 1.1;

Fuel system weight:

where is the mass of fuel spent on the flight;

The weight coefficient assumed for the fuel system is 0.09;

The weight of the helicopter landing gear is:

where is the weight coefficient depending on the chassis design. Since the designed helicopter has a retractable landing gear, then

The mass of the helicopter electrical equipment is calculated using formula (5.9.5):

where is the distance between the axes of the main and tail rotors;

Number of main rotor blades;

R- radius of the main rotor;

Relative elongation of the main rotor blades;

and - weighting coefficients for electrical wires and other electrical equipment,

Weight of other helicopter equipment:

where is a weighting coefficient whose value is 1.

5.10 Calculation of helicopter take-off weight of the second approximation

The mass of an empty helicopter is equal to the sum of the masses of the main units:

Second approach helicopter take-off weight:

We determine the relative deviation of the masses of the first and second approximations:

The relative deviation of the masses of the first and second approximations satisfies the condition. This means that the calculation of the helicopter parameters was performed correctly.

6 Description of the helicopter layout

The designed helicopter is made according to a single-rotor design with a tail rotor, two gas turbine engines and a skid landing gear.

The fuselage is semi-monocoque. The load-bearing power elements of the fuselage are made of aluminum alloys and have an anti-corrosion coating. The forward part of the fuselage with the cockpit canopy and the engine nacelle hoods are made of a composite material based on fiberglass. The pilot's cabin has two doors, the windows are equipped with an anti-icing system and windshield wipers. The left and right doors of the cargo-passenger cabin and an additional hatch in the rear part of the fuselage ensure the convenience of loading sick and injured people on stretchers, as well as large-sized cargo. The skid chassis is made of solid bent metal pipes. The springs are covered with fairings. The tail support prevents the tail rotor from touching the landing pad. The main and tail rotor blades are made of composite materials based on fiberglass and can be equipped with an anti-icing system. The four-blade main rotor hub is hingeless, made of two intersecting fiberglass beams, to each of which two blades are attached. Two-blade tail rotor hub with a common horizontal joint. Fuel tanks with a total capacity of 850 liters are located in the fuselage floor. The helicopter control system is fly-by-wire without mechanical wiring, having four times digital redundancy and two times redundant independent electrical power supply. Modern flight and navigation equipment ensures flights in simple and adverse weather conditions, as well as flights under VFR and IFR rules. Parameters of helicopter systems are monitored using an on-board information system control BISK-A. The helicopter is equipped with a warning and emergency signaling system.

The helicopter can be equipped with a water landing system, as well as fire extinguishing and chemical spraying systems.

The power plant is two gas turbine engines GTD-1000T with a total power of 2×735.51 kW. The engines are mounted on the fuselage in separate nacelles. The air intakes are side, equipped with dust protection devices. The side panels of the gondolas hinge on hinges to form service platforms. The engine shafts extend at an angle to the central gearbox and accessory compartment. The exhaust nozzles of the engines are deflected outward at an angle of 24". To protect against sand, filters are installed that prevent 90% of the penetration of particles with a diameter of more than 20 microns into the engine.

The transmission consists of engine gearboxes, intermediate gearboxes, angular gearboxes, main gearbox, shaft and auxiliary gearbox. power plant, shaft and angular gearbox of the steering wheel. The transmission system uses titanium alloys.

The electrical system consists of two isolated circuits, one of which is powered by an alternating current generator producing a voltage of 115-120V, and the second circuit is powered by a DC generator with a voltage of 28V. The generators are driven from the main rotor gearbox.

The control is duplicated, with rigid and cable wiring and hydraulic boosters driven from the main and backup hydraulic systems. The AP-34B four-channel autopilot ensures stabilization of the helicopter in flight in roll, heading, pitch and altitude. Main hydraulic system provides power to all hydraulic units, and the backup one - only to the hydraulic boosters.

The heating and ventilation system supplies heated or cold air to the crew and passenger cabins; the anti-icing system protects the main and tail rotor blades, the front windows of the cockpit and engine air intakes from icing.

Communication equipment includes command HF-band - "Yurok", intercom device SPU-34.

Bibliography

1. Helicopter design / V.S. Krivtsov, L.I. Losev, Ya.S. Karpov. - Textbook. - Kharkov: Nat. aerospace University "Khark" aviation Institute", 2003. - 344 p.
2. www.wikipedia.ru
3. www.airwar.ru
4. narod.ru
5. http://www.vertolet-media.ru/helicopters/kvz/ansat/

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PHYSICS OF THE ROTOR

A magnificent machine - a helicopter! Its remarkable qualities make it indispensable in thousands of cases. Only a helicopter can take off and land vertically, hang motionless in the air, move sideways and even tail first.

Where do such wonderful opportunities come from? What is the physics of its flight7 Let's try to briefly answer these questions.

A helicopter rotor creates lift. The propeller blades are the same propellers. Installed at a certain angle to the horizon, they behave like a wing in the flow of incoming air: pressure arises under the lower plane of the blades, and vacuum occurs above it. The greater this difference, the greater the lift. When the lifting force exceeds the weight of the helicopter, it takes off, but if the opposite happens, the helicopter descends.

If on an airplane wing the lift force appears only when the airplane is moving, then on the “wing” of a helicopter it appears even when the helicopter is standing still: the “wing” is moving. This is the main thing.

But the helicopter gained altitude. Now he needs to fly forward. How to do it? The screw only creates upward thrust! Let's look into the cockpit at this moment. He turned the control stick away from him. The helicopter tilted slightly on its nose and flew forward. Why?

The control knob is connected to an ingenious device - a transfer machine. This mechanism, extremely convenient for controlling a helicopter, was invented during his student years by academician B. N. Yuryev. Its design is quite complex, but its purpose is to enable the pilot to change the angle of the blades to the horizon at will.

It is not difficult to understand that during a horizontal flight of a helicopter, the blades of its blades move relative to the surrounding air with at different speeds. The blade that goes forward moves towards the air flow, and the blade that turns back moves along the flow. Therefore, the speed of the blade, and with it the lifting force, will be higher when the blade moves forward. The propeller will tend to turn the helicopter on its side.

To prevent this from happening, the nonstrunters connected the blades to the axis movably, on hinges. Then the forward blade with the larger lifting force began to soar and flap. But this movement was no longer transmitted to the helicopter; it flew calmly. Thanks to the flapping motion of the blade, its lifting force remained constant throughout the revolution.

However, this did not solve the problem of moving forward. After all, you need to change the direction of the propeller thrust and force the helicopter to move horizontally. This was made possible by the swashplate. It continuously changes the angle of each propeller blade so that the greatest lift occurs approximately in the rear sector of its rotation. The resulting thrust force of the main rotor tilts, and the helicopter, also tilting, begins to move forward.

It took a long time for such a reliable and convenient helicopter control device to be created. A device for controlling the direction of flight did not appear immediately.

You, of course, know that a helicopter does not have a rudder. Yes, it is not needed by a rotorcraft. It is replaced by a small propeller mounted on the tail. If the pilot tried to turn it off, the helicopter would turn itself. Yes, it turned so that it would begin to rotate faster and faster in the direction opposite to the rotation of the main rotor. This is a consequence of the reactive torque that occurs when the main rotor rotates. The tail rotor prevents the tail of the helicopter from turning under the influence of the reaction torque and balances it. And if necessary, the pilot will increase or decrease the tail rotor thrust. Then the helicopter will turn in the right direction.

Sometimes they do without a tail rotor altogether, installing two main rotors on helicopters, rotating towards each other. Reactive moments in this case, of course, are destroyed.

This is how the “aerial all-terrain vehicle” flies and the tireless worker - the helicopter.

INTRODUCTION

Helicopter design is a complex process that develops over time, divided into interrelated project stages and stages. The aircraft being created must satisfy technical requirements and comply with the technical and economic characteristics specified in the design specifications. Technical task contains the initial description of the helicopter and its flight performance characteristics, ensuring high economic efficiency and competitiveness of the designed vehicle, namely: load capacity, flight speed, range, static and dynamic ceiling, service life, durability and cost.

The terms of reference are clarified at the stage of pre-design research, during which a patent search and analysis of existing technical solutions, research and development work. The main task of pre-design research is the search and experimental verification of new principles for the functioning of the designed object and its elements.

At the preliminary design stage, an aerodynamic design is selected, the appearance of the helicopter is formed, and the main parameters are calculated to ensure the achievement of the specified flight performance characteristics. These parameters include: the weight of the helicopter, the power of the propulsion system, the dimensions of the main and tail rotors, the weight of fuel, the weight of instrumentation and special equipment. The calculation results are used in developing the helicopter layout and drawing up a centering sheet to determine the position of the center of mass.

The design of individual helicopter units and components, taking into account the selected technical solutions, is carried out at the development stage technical project. In this case, the parameters of the designed units must satisfy the values ​​corresponding preliminary design. Some parameters can be refined in order to optimize the design. At technical design aerodynamic strength and kinematic calculations of components, selection of structural materials and design schemes are performed.

At the detailed design stage, working and assembly drawings of the helicopter, specifications, picking lists and other materials are prepared. technical documentation in accordance with accepted standards

This paper presents a methodology for calculating helicopter parameters at the preliminary design stage, which is used to complete a course project in the discipline "Helicopter Design".

1. First approximation calculation of helicopter take-off weight

where is the mass of the payload, kg;

Crew weight, kg.

Range of flight

2. Calculation of helicopter rotor parameters

2.1 Radius R, m, single-rotor helicopter main rotor calculated by the formula:

where is the take-off weight of the helicopter, kg;

g - free fall acceleration equal to 9.81 m/s 2;

p - specific load on the area swept by the main rotor,

=3,14.

Specific load value p the area swept by the screw is selected according to the recommendations presented in work /1/: where p= 280

We take the radius of the rotor equal to R= 7.9

Angular velocity , s -1, rotation of the main rotor is limited by the value of the peripheral speed R ends of the blades, which depends on the take-off weight of the helicopter and amounted to R= 232 m/s.

C -1.

RPM

2.2 Relative air densities on static and dynamic ceilings

2.3 Calculation of economic speed at the ground and on a dynamic ceiling

The relative area of ​​the equivalent harmful plate is determined:

Where S uh= 2.5

The value of economic speed near the ground is calculated V h, km/h:

Where I = 1,09…1,10 - induction coefficient.

Km/hour.

The value of the economic speed on the dynamic ceiling is calculated V ding, km/h:

Where I = 1,09…1,10 - induction coefficient.

Km/hour.

2.4 The relative values ​​of the maximum and economic on the dynamic ceiling are calculated horizontal flight speeds:

Where V max=250 km/h and V ding=182.298 km/h - flight speed;

R=232 m/s - peripheral speed of the blades.

2.5 Calculation of the permissible ratios of the thrust coefficient to the rotor filling for the maximum speed at the ground and for the economic speed at the dynamic ceiling:

at

2.6 Main rotor thrust coefficients at the ground and on the dynamic ceiling:

2.7 Calculation of rotor filling:

Main rotor filling calculated for cases of flight at maximum and economic speeds:

As a calculated fill value main rotor is taken to be the largest value of Vmax And V ding:

We accept

Chord length b and relative elongation rotor blades will be equal to:

Where zl is the number of main rotor blades (zl = 3)

2.8 Relative increase in rotor thrust to compensate for the aerodynamic drag of the fuselage and horizontal tail:

where Sф is the area of ​​the horizontal projection of the fuselage;

S th - area of ​​the horizontal tail.

S f =10 m 2;

S th =1.5 m2.

3. Calculation of the power of the helicopter propulsion system.

3.1 Calculation of power when hanging on a static ceiling:

The specific power required to drive the main rotor in hover mode on a statistical ceiling is calculated by the formula:

Where N H st- required power, W;

m 0 - take-off weight, kg;

g - free fall acceleration, m/s 2;

p - specific load on the area swept by the main rotor, N/m 2;

st - relative air density at the height of the static ceiling;

0 - relative efficiency main rotor in hover mode ( 0 =0.75);

Relative increase in main rotor thrust to balance the aerodynamic drag of the fuselage and horizontal tail:

3.2 Calculation of power density in level flight at maximum speed

The specific power required to drive the main rotor in horizontal flight at maximum speed is calculated by the formula:

where is the peripheral speed of the ends of the blades;

Relative equivalent harmful plate;

I uh- induction coefficient, determined depending on the flight speed according to the following formulas:

At km/h,

At km/h.

3.3 Calculation of power density in flight on a dynamic ceiling at economic speed

The specific power for driving a main rotor on a dynamic ceiling is:

Where ding- relative air density on the dynamic ceiling,

V ding- economic speed of the helicopter on a dynamic ceiling,

3.4 Calculation of specific power in flight near the ground at economic speed in the event of one engine failure during takeoff

The specific power required to continue takeoff at economic speed when one engine fails is calculated by the formula:

where is the economic speed at the ground,

3.5 Calculation of specific reduced powers for various flight cases

3.5.1 The specific reduced power when hanging on a static ceiling is equal to:

where is the specific throttling characteristic, which depends on the height of the static ceiling H st and is calculated by the formula:

0 - power utilization factor of the propulsion system in hovering mode, the value of which depends on the take-off weight of the helicopter m 0 :

At m 0 < 10 тонн

At 10 25 tons

At m 0 > 25 tons

3.5.2 Specific reduced power in horizontal flight at maximum speed is equal to:

where is the power utilization factor at maximum flight speed,

Throttle characteristics of engines depending on flight speed V max :

3.5.3 Specific reduced power in flight on a dynamic ceiling at economic speed V ding is equal to:

where is the power utilization factor at economic flight speed,

and - degrees of engine throttling, depending on the height of the dynamic ceiling H and flight speed V ding in accordance with the following throttle characteristics:

3.5.4 The specific reduced power in flight near the ground at economic speed with the failure of one engine on takeoff is equal to:

where is the power utilization factor at economic flight speed,

The degree of engine throttling in emergency mode,

n =2 - number of helicopter engines.

3.5.5 Calculation of the required power of the propulsion system

To calculate the required power of the propulsion system, the maximum value of the specific reduced power is selected:

Required power N helicopter propulsion system will be equal to:

Where m 0 1 - helicopter take-off weight,

g = 9.81 m 2/s - free fall acceleration.

W,

3.6 Selection of engines

We accept two turboshaft engines VK-2500 (TV3-117VMA-SB3) total power of each N=1.405 10 6 W

The VK-2500 engine (TV3-117VMA-SB3) is intended for installation on new generation helicopters, as well as for replacing engines on existing helicopters to improve their flight performance. It was created on the basis of the serial certified TV3-117VMA engine and is produced at the Federal State Unitary Enterprise “Plant named after V.Ya. Klimov."

4. Calculation of fuel mass

To calculate the mass of fuel that provides a given flight range, it is necessary to determine the cruising speed V cr. The cruising speed is calculated using the method of successive approximations in the following sequence:

a) the value of the first approach cruising speed is taken:

km/hour;

b) the induction coefficient is calculated I uh:

At km/h

At km/h

c) the specific power required to drive the main rotor in flight at cruising mode is determined:

where is the maximum value of the specific reduced power of the propulsion system,

Power change coefficient depending on flight speed V cr 1, calculated by the formula:

d) The second approach cruising speed is calculated:

e) The relative deviation of the speeds of the first and second approximations is determined:

When the cruising speed of the first approximation is clarified V cr 1, it is assumed to be equal to the calculated speed of the second approximation. Then the calculation is repeated from point b) and ends with the condition .

Specific fuel consumption is calculated using the formula:

where is the coefficient of change in specific fuel consumption depending on the operating mode of the engines,

Coefficient of change in specific fuel consumption depending on flight speed,

Specific fuel consumption at takeoff.

In case of flight in cruising mode the following is accepted:

At kW;

At kW.

Kg/W hour,

Mass of fuel consumed for flight m T will be equal to:

where is the specific power consumed at cruising speed,

Cruising speed,

L - range of flight.

5. Determination of the mass of helicopter components and assemblies.

5.1 The mass of the main rotor blades is determined by the formula:

Where R - rotor radius,

- filling the main rotor,

Kg,

5.2 The mass of the main rotor hub is calculated using the formula:

Where k Tue- weight coefficient of bushings of modern designs,

k l- coefficient of influence of the number of blades on the mass of the hub.

In the calculation you can take:

Kg/kN,

therefore, as a result of transformations we get:

To determine the mass of the main rotor hub, it is necessary to calculate the centrifugal force acting on the blades N Central Bank(in kN):

KN,

kg.

5.3 Booster control system weight, which includes the swashplate, hydraulic boosters, and the main rotor hydraulic control system is calculated using the formula:

Where b- chord of the blade,

k boo- the weight coefficient of the booster control system, which can be taken equal to 13.2 kg/m3.

Kg.

5.4 Weight of manual control system:

Where k RU- the weight coefficient of the manual control system, taken for single-rotor helicopters to be equal to 25 kg/m.

Kg.

5.5 The mass of the main gearbox depends on the torque on the main rotor shaft and is calculated by the formula:

Where k edit- weight coefficient, the average value of which is 0.0748 kg/(Nm) 0.8.

The maximum torque on the main rotor shaft is determined through the reduced power of the propulsion system N and propeller speed :

Where 0 - power utilization factor of the propulsion system, the value of which is taken depending on the take-off weight of the helicopter m 0 :

At m 0 < 10 тонн

At 10 25 tons

At m 0 > 25 tons

N m,

Main gearbox weight:

Kg.

5.6 To determine the mass of the tail rotor drive units, its thrust is calculated T ditch :

Where M nv- torque on the main rotor shaft,

L ditch- the distance between the axes of the main and tail rotors.

The distance between the axes of the main and tail rotors is equal to the sum of their radii and clearance between the ends of their blades:

Where - gap taken equal to 0.15...0.2 m,

The radius of the tail rotor, which, depending on the take-off weight of the helicopter, is:

When t,

When t,

At t.

Power N ditch, spent on rotating the tail rotor, is calculated by the formula:

Where 0 - relative efficiency of the tail rotor, which can be taken equal to 0.6...0.65.

W,

Torque M ditch transmitted by the steering shaft is equal to:

N m,

where is the speed of the steering shaft,

s -1,

Torque transmitted by the transmission shaft, N m, at rotation speed n V= 3000 rpm equal to:

N m,

Weight m V transmission shaft:

Wherek V- weight coefficient for the transmission shaft, which is equal to 0.0318 kg/(Nm) 0.67.

Weight m etc intermediate gearbox is equal to:

Where k etc- weight coefficient for the intermediate gearbox, equal to 0.137 kg/(Nm) 0.8.

Mass of the tail gearbox rotating the tail rotor:

Where k xp- weight coefficient for the tail gearbox, the value of which is 0.105 kg/(Nm) 0.8

kg.

5.7 The mass and main dimensions of the tail rotor are calculated depending on its thrust T ditch .

Thrust coefficient C ditch tail rotor is equal to:

Filling the tail rotor blades ditch is calculated in the same way as for the main rotor:

where is the permissible value of the ratio of the thrust coefficient to the tail rotor filling.

Chord length b ditch and relative elongation ditch tail rotor blades is calculated using the formulas:

Where z ditch- number of tail rotor blades.

Tail rotor blade weight m lr calculated using the empirical formula:

Centrifugal force value N cbd, acting on the tail rotor blades and perceived by the hub hinges,

Tail rotor hub weight m Tue is calculated using the same formula as for the main rotor:

Where N Central Bank- centrifugal force acting on the blade,

k Tue- weight coefficient for the bushing, taken equal to 0.0527 kg/kN 1.35

k z- weight coefficient depending on the number of blades and calculated by the formula:

5.8 Calculation of the mass of the helicopter propulsion system

Specific gravity of the helicopter propulsion system dv calculated using the empirical formula:

Where N- power of the propulsion system.

The mass of the propulsion system will be equal to:

kg.

5.9 Calculation of the weight of the fuselage and helicopter equipment

The mass of the helicopter fuselage is calculated by the formula:

Where S ohm- area of ​​the washed surface of the fuselage, which is determined by the formula:

M 2,

m 0 - first approach take-off weight,

k f- coefficient equal to 1.7.

kg,

Fuel system weight:

Where m T- mass of fuel spent on flight,

k ts- weight coefficient assumed for the fuel system to be 0.09.

Kg,

The weight of the helicopter landing gear is:

Where k w- weight coefficient depending on the chassis design:

For non-retractable landing gear,

For retractable landing gear.

kg,

The mass of the helicopter electrical equipment is calculated using the formula:

Where L ditch- the distance between the axes of the main and tail rotors,

z l- number of main rotor blades,

R - rotor radius,

l- relative elongation of the main rotor blades,

k etc And k el- weighting coefficients for electrical wires and other electrical equipment, the values ​​of which are equal to:

kg,

Weight of other helicopter equipment:

Where k etc- weighting coefficient, the value of which is 2.

kg.

5.10 Calculation of helicopter take-off weight of the second approximation

The mass of an empty helicopter is equal to the sum of the masses of the main units:

Second approach helicopter take-off weight m 02 will be equal to the sum:

Where m T - mass of fuel,

m gr- payload mass,

m ek- weight of the crew.

kg,

6. Description of the helicopter layout

The designed helicopter is made according to a single-rotor design with a tail rotor, two gas turbine engines and two-legged skis. The helicopter fuselage has a frame structure and consists of the nose and central parts, tail and end beams. In the bow there is a two-seat crew cabin consisting of two pilots. Cabin glazing provides good review, the right and left sliding blisters are equipped with emergency release mechanisms. In the central part there is a cabin with dimensions of 6.8 x 2.05 x 1.7 m, and a central sliding door with dimensions of 0.62 x 1.4 m with an emergency release mechanism. The cargo compartment is designed to transport cargo weighing up to 2 tons and is equipped with folding seats for 12 passengers, as well as attachment points for 5 stretchers. In the passenger version, the cabin contains 12 seats, installed with a pitch of 0.5 m and a passage of 0.25 m; and in the rear part there is an opening for the rear entrance door, consisting of two doors.

The tail boom is a riveted beam-stringer type structure with working skin, equipped with units for attaching a controlled stabilizer and a tail support.

Stabilizer with a size of 2.2 m and an area of ​​1.5 m 2 with a NACA 0012 profile of a single-spar design, with a set of ribs and duralumin and fabric covering.

Double-support skis, self-orienting front support, dimensions 500 x 185 mm, shaped main supports with liquid-gas double-chamber shock absorbers, dimensions 865 x 280 mm. The tail support consists of two struts, a shock absorber and a support heel; ski track 2m, ski base 3.5m.

Main rotor with hinged blades, hydraulic dampers and pendulum vibration dampers, installed with a forward inclination of 4° 30". All-metal blades consist of a pressed spar made of AVT-1 aluminum alloy, hardened by work hardening with steel hinges on the vibration stand, tail section, steel tip and tip The blades have a rectangular shape in plan with a chord of 0.67 m and NACA 230 profiles and a geometric twist of 5%, the peripheral speed of the blade tips is 200 m/s, the blades are equipped with a visual alarm system for spar damage and an electrothermal anti-icing device.

The tail rotor with a diameter of 1.44 m is three-blade, pushing, with a cardan-type hub and all-metal blades of rectangular shape in plan, with a chord of 0.51 m and a NACA 230M profile.

The power plant consists of two turboshaft gas turbine engines with a free turbine VK-2500 (TV3-117VMA-SB3) of the St. Petersburg NPO named after. V.Ya.Klimov total power of each N=1405 W, installed on top of the fuselage and closed by a common hood with opening flaps. The engine has a nine-stage axial compressor, an annular combustion chamber and a two-stage turbine. The engines are equipped with dust protection devices.

The transmission consists of main, intermediate and tail gearboxes, brake shafts, and a main rotor. The VR-8A three-stage main gearbox provides power transmission from the engines to the main rotor, tail rotor and fan for cooling, engine oil coolers and the main gearbox; The total capacity of the oil system is 60 kg.

The control is duplicated, with rigid and cable wiring and hydraulic boosters driven from the main and backup hydraulic systems. The AP-34B four-channel autopilot ensures stabilization of the helicopter in flight in roll, heading, pitch and altitude. The main hydraulic system provides power to all hydraulic units, and the backup system provides power only to the hydraulic boosters.

The heating and ventilation system supplies heated or cold air to the crew and passenger cabins; the anti-icing system protects the main and tail rotor blades, the front windows of the cockpit and engine air intakes from icing.

Equipment for instrument flights in difficult meteorological conditions day and night includes two attitude indicators, two NV speed indicators, a combined heading system GMK-1A, an automatic radio compass, and an RV-3 radio altimeter.

Communication equipment includes command VHF radio stations R-860 and R-828, communications HF radio stations R-842 and Karat, and an aircraft intercom SPU-7.

7. Helicopter alignment calculation

Table 1. Empty helicopter alignment sheet

Static moments are calculated M cx i And M su i relative to coordinate axes:

The coordinates of the center of mass of the entire helicopter are calculated using the formulas :

Table 2. Alignment sheet with maximum load

Table 3. Alignment sheet with 5% remaining fuel and full commercial load

Center of mass coordinates empty helicopter: x0 =-0.003; y0 =-1.4524;

Coordinates of the center of mass with maximum load: x0 =0.0293; y0 =-2.0135;

Coordinates of the center of mass with 5% fuel remaining and full commercial load viscous: x 0 = -0.0678; y 0 = -1,7709.

Conclusion

In this course project, calculations were made of the take-off weight of the helicopter, the mass of its components and assemblies, as well as the layout of the helicopter. During the assembly process, the alignment of the helicopter was clarified, the calculation of which is preceded by the preparation of a weight report based on weight calculations of the units and power plant, lists of equipment, equipment, cargo, etc. The purpose of the design is to determine the optimal combination of the main parameters of the helicopter and its systems that ensure the fulfillment of specified requirements.

A helicopter is a rotary-wing machine in which lift and thrust are generated by a propeller. The main rotor serves to support and move the helicopter in the air. When rotating in a horizontal plane, the main rotor creates an upward thrust (T) and acts as a lifting force (Y). When the main rotor thrust is greater than the weight of the helicopter (G), the helicopter will take off from the ground without a takeoff run and begin a vertical climb. If the weight of the helicopter and the thrust of the main rotor are equal, the helicopter will hang motionless in the air. For a vertical descent, it is enough to make the main rotor thrust slightly less than the weight of the helicopter. The forward motion of the helicopter (P) is ensured by tilting the plane of rotation of the main rotor using the rotor control system. The inclination of the rotor rotation plane causes a corresponding inclination of the total aerodynamic force, while its vertical component will keep the helicopter in the air, and the horizontal component will cause the helicopter to move forward in the corresponding direction.

Figure 1. Force distribution diagram

Helicopter design

The fuselage is the main part of the helicopter structure, serving to connect all its parts into one whole, as well as to accommodate the crew, passengers, cargo, and equipment. It has a tail and end beams for placing the tail rotor outside the rotation zone of the main rotor, and the wing (on some helicopters, the wing is installed to increase the maximum flight speed due to partial unloading of the main rotor (MI-24)). Power plant (engines)is a source of mechanical energy to drive the main and tail rotors into rotation. It includes engines and systems that ensure their operation (fuel, oil, cooling system, engine starting system, etc.). The main rotor (RO) serves to support and move the helicopter in the air, and consists of blades and a main rotor hub. The tail rotor serves to balance the reaction torque that occurs during rotation of the main rotor and for directional control of the helicopter. The thrust force of the tail rotor creates a moment relative to the helicopter's center of gravity, which balances the reactive moment of the main rotor. To turn the helicopter, it is enough to change the amount of tail rotor thrust. The tail rotor also consists of blades and a bushing. The main rotor is controlled using a special device called a swashplate. The tail rotor is controlled by pedals. Take-off and landing devices serve as a support for the helicopter when parked and provide movement of the helicopter on the ground, takeoff and landing. To soften shocks and shocks, they are equipped with shock absorbers. Take-off and landing devices can be made in the form of a wheeled chassis, floats and skis

Fig.2 Main parts of the helicopter:

1 — fuselage; 2 - aircraft engines; 3 — main rotor (carrying system); 4 — transmission; 5 — tail rotor; 6 - end beam; 7 - stabilizer; 8 — tail boom; 9 — chassis

The principle of creating lift by a propeller and the propeller control system

During vertical flightThe total aerodynamic force of the main rotor will be expressed as the product of the mass of air flowing through the surface swept by the main rotor in one second and the speed of the outgoing jet:

Where πD 2/4 - surface area swept by the main rotor;V—flight speed in m/sec; ρ — air density;u —speed of outgoing jet in m/sec.

In fact, the thrust force of the propeller is equal to the reaction force when accelerating the air flow

In order for a helicopter to move forward, the plane of rotation of the rotor must be skewed, and the change in the plane of rotation is achieved not by tilting the main rotor hub (although the visual effect may be just that), but by changing the position of the blade in different parts of the quadrants of the circumscribed circle.

The rotor blades, describing a full circle around the axis as it rotates, are flown around by the oncoming air flow in different ways. A full circle is 360º. Then we take the rear position of the blade as 0º and then every 90º full revolution. So, a blade in the range from 0º to 180º is an advancing blade, and from 180º to 360º is a retreating blade. The principle of this name, I think, is clear. The advancing blade moves towards the oncoming air flow, and the total speed of its movement relative to this flow increases because the flow itself, in turn, moves towards it. After all, the helicopter is flying forward. Lifting force also increases accordingly.

Fig.3 Change in free-stream velocities during rotor rotation for the MI-1 helicopter (average flight speeds).

For a retreating blade, the picture is the opposite. The speed with which this blade seems to “run away” from it is subtracted from the speed of the oncoming flow. As a result, we have less lift. It turns out there is a serious difference in forces on the right and left sides of the propeller and hence the obvious turning point. In this state of affairs, the helicopter will tend to roll over when attempting to move forward. Such things took place during the first experience of creating rotorcraft.

To prevent this from happening, the designers used one trick. The fact is that the main rotor blades are secured to a sleeve (this is such a massive unit mounted on the output shaft), but not rigidly. They are connected to it using special hinges (or similar devices). There are three types of hinges: horizontal, vertical and axial.

Now let's see what will happen to the blade, which is suspended from the axis of rotation on hinges. So, our blade rotates at a constant speed without any external control inputs.

Rice. 4 Forces acting on a blade suspended from a propeller hub on hinges.

From From 0º to 90º, the speed of flow around the blade increases, which means that the lift force also increases. But! The blade is now suspended on a horizontal hinge. As a result of the excess lifting force, it turns in a horizontal hinge and begins to rise upward (experts say “makes a swing”). At the same time, due to an increase in drag (after all, the flow speed has increased), the blade tilts back, lagging behind the rotation of the propeller axis. This is exactly what the vertical ball-nier serves for.

However, when flapping, it turns out that the air relative to the blade also acquires some downward movement and, thus, the angle of attack relative to the oncoming flow decreases. That is, the growth of excess lift slows down. This slowdown is additionally influenced by the absence of control action. This means that the swashplate rod attached to the blade retains its position unchanged, and the blade, flapping, is forced to rotate in its axial hinge, held by the rod and, thereby, reducing its installation angle or angle of attack in relation to the oncoming flow. (The picture of what is happening is in the figure. Here Y is the lift force, X is the drag force, Vy is the vertical movement of air, α is the angle of attack.)

Fig.5 Picture of changes in the speed and angle of attack of the oncoming flow during rotation of the main rotor blade.

To the point 90º excess lift will continue to increase, but at an increasingly slower rate due to the above. After 90º this force will decrease, but due to its presence the blade will continue to move upward, albeit more and more slowly. It will reach its maximum swing height after slightly exceeding the 180º point. This happens because the blade has a certain weight, and inertia forces also act on it.

With further rotation, the blade becomes retreating, and all the same processes act on it, but in the opposite direction. The magnitude of the lifting force drops and the centrifugal force, together with the weight force, begins to lower it down. However, at the same time, the angles of attack for the oncoming flow increase (now the air is moving upward relative to the blade), and the installation angle of the blade increases due to the immobility of the rods helicopter swashplate . Everything that happens maintains the lift of the retreating blade at the required level. The blade continues to descend and reaches its minimum swing height somewhere after the 0º point, again due to inertial forces.

Thus, when the main rotor rotates, the helicopter blades seem to “waving” or they also say “fluttering”. However, you are unlikely to notice this fluttering with the naked eye, so to speak. The lift of the blades upward (as well as their deflection back in the vertical hinge) is very insignificant. The fact is that the centrifugal force has a very strong stabilizing effect on the blades. The lifting force, for example, is 10 times greater than the weight of the blade, and the centrifugal force is 100 times greater. It is the centrifugal force that turns a seemingly “soft” blade that bends in a stationary position into a hard, durable and perfectly functioning element of a helicopter’s main rotor.

However, despite its insignificance, the vertical deflection of the blades is present, and the main rotor, when rotating, describes a cone, albeit a very gentle one. The base of this cone is propeller rotation plane(see Fig.1.)

To impart forward motion to the helicopter, this plane must be tilted so that the horizontal component of the total aerodynamic force appears, that is, the horizontal thrust of the propeller. In other words, you need to tilt the entire imaginary cone of rotation of the propeller. If the helicopter needs to move forward, then the cone must be tilted forward.

Based on the description of the movement of the blade when the propeller rotates, this means that the blade in the 180º position should fall, and in the 0º (360º) position it should rise. That is, at point 180º the lifting force should decrease, and at point 0º (360º) it should increase. And this, in turn, can be done by reducing the installation angle of the blade at the 180º point and increasing it at the 0º (360º) point. Similar things should happen when the helicopter moves in other directions. Only in this case, naturally, similar changes in the position of the blades will occur at other corner points.

It is clear that at intermediate angles of rotation of the propeller between the indicated points, the installation angles of the blade must occupy intermediate positions, that is, the installation angle of the blade changes as it moves in a circle gradually, cyclically. This is called the cyclic installation angle of the blade ( cyclic propeller pitch). I highlight this name because there is also a general pitch of the propeller (the general angle of installation of the blades). It changes simultaneously on all blades by the same amount. This is usually done to increase the overall lift of the rotor.

Such actions are performed helicopter swashplate . It changes the installation angle of the main rotor blades (rotor pitch) by rotating them in the axial hinges by means of rods attached to them. Typically, there are always two control channels: pitch and roll, as well as a channel for changing the overall pitch of the main rotor.

Pitch means the angular position of the aircraft relative to its transverse axis (nose up-down), akren, respectively, relative to its longitudinal axis (tilt left-right).

Structurally helicopter swashplate It is quite complicated, but its structure can be explained using the example of a similar unit of a helicopter model. The model machine, of course, is simpler in design than its older brother, but the principle is absolutely the same.

Rice. 6 Helicopter model swashplate

This is a two-blade helicopter. The angular position of each blade is controlled through rods6. These rods are connected to the so-called inner plate2 (made of white metal). It rotates with the propeller and in steady state is parallel to the plane of rotation of the propeller. But it can change its angular position (tilt), since it is fixed to the axis of the screw through a ball joint3. When changing its inclination (angular position), it affects the rods6, which, in turn, act on the blades, turning them in the axial hinges and thereby changing the cyclic pitch of the propeller.

Inner plate at the same time it is the inner race of the bearing, the outer race of which is the outer plate of the screw1. It does not rotate, but can change its tilt (angular position) under the influence of control via the pitch channel4 and roll channel5. Changing its inclination under the influence of control, the outer plate changes the inclination of the inner plate and, as a result, the inclination of the rotor rotation plane. As a result, the helicopter flies in the right direction.

The overall pitch of the screw is changed by moving the inner plate2 along the screw axis using a mechanism7. In this case, the installation angle changes on both blades at once.

For a better understanding, I’m including a few more illustrations of a swashplate screw hub.

Rice. 7 Screw bushing with swashplate (diagram).

Rice. 8 Rotation of the blade in the vertical hinge of the main rotor hub.

Rice. 9 Main rotor hub of the MI-8 helicopter

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