1. By appointment.
By appointment, civil and military aircraft are distinguished.
To civil aircraft relate:
Transport (passenger, cargo-passenger, cargo),
Sports, record (for setting records of speed, rate of climb, altitude, flight range, etc.), training,
Tourist,
administrative,
agricultural,
Special purpose (for example, for rescue work, teleoperated),
Experimental.
Rice. 6. Classification of passenger aircraft
Military aircraft designed to destroy air, ground (sea) targets or to perform other combat missions. They are divided into:
Fighters - for air combat,
Bombers - to destroy objects behind enemy lines and to bombard troops and fortifications,
scouts,
transport,
communications aircraft,
Sanitary.
2. By design.
The classification of aircraft by design is based on external signs:
The number and arrangement of the wings,
The shape and location of plumage,
The location of the engines
chassis type,
Fuselage type.
Schematically, the classification of aircraft by design is shown in Fig. 7.
Rice. 7. Main types of aircraft
depending from the number of wings distinguish:
Monoplanes are airplanes with one wing.
Biplanes - aircraft with two wings, one above the other,
One and a half gliders are biplanes in which one of the wings is shorter than the other.
Biplanes are more maneuverable than monoplanes, but have more drag, which reduces the speed of the aircraft. Therefore, most modern aircraft are carried out according to the monoplane scheme.
depending from the location of the wing regarding the fuselage, monoplanes are divided into:
low planes,
medium plans,
High planes.
According to the location of the plumage distinguish:
Aircraft of the classical scheme (the plumage is located behind the wing) - fig. 8a,
Airplanes of the "duck" type (horizontal tail is located in front of the wing) - fig. 8b,
Aircraft of the "tailless" type (the plumage is located on the wing) - fig. 8c.
Rice. 8. Plumage layouts
The classic scheme of aircraft can be:
With a single-tail plumage,
With spaced vertical (multi-keel) plumage,
With V-shaped plumage.
depending on chassis type aircraft are divided into:
land,
seaplanes,
Amphibians (seaplanes equipped with wheeled landing gear).
By engine type distinguish aircraft:
propeller,
turboprop,
Turbojet.
When choosing the installation location of engines, their number and type, take into account:
Aerodynamic drag generated by engines
The turning moment that occurs when one of the engines fails,
The complexity of the device air intakes,
Ability to service and replace engines,
Noise level in the passenger compartment, etc.
depending from airspeed distinguish aircraft:
Subsonic (aircraft speed corresponds to the Mach number M< 1),
Supersonic (1 ≤ M< 5),
In accordance with the code of the International Aviation Federation aircrafts divided into classes, for example:
Class BUT- free balloons;
Class AT- airships;
Class With- aircraft, helicopters, seaplanes, etc.;
Class S- space models.
In addition, the class With divided into four groups, depending on the power plant. Also, all civil aircraft are grouped into classes depending on their takeoff weight:
Class one - 75 t and more;
Second class - 30-75 t;
Class three - 10-30 t;
Class four - up to 10 t.
Type classification aircraft.
Aircraft - an aircraft maintained in the atmosphere due to its interaction with air, which is different from interaction with air reflected from the earth's surface.
An airplane is a heavier-than-air aircraft for flights in the atmosphere with the help of a power plant that creates thrust and a fixed wing, on which an aerodynamic lift force is generated when moving in the air.
Aircraft can be classified according to many characteristics, but they are interconnected and form a single system of aircraft, which is in constant motion under the influence of many market factors.
Depending on the nature of the aircraft operation civil aviation can be classified into:
1) general aviation aircraft (GA);
2) commercial aviation aircraft.
Aircraft that are in regular operation, that is, in the field of activity of commercial airlines that carry passengers and cargo on a schedule, are classified as commercial aviation. The use of an aircraft for personal or business purposes classifies it as a general aviation aircraft.
In recent years, there has been an increase in the popularity of general purpose aircraft, as they are able to perform tasks that are unusual for commercial aviation - transportation of small cargoes, agricultural work, patrolling, pilot training, aviation sports, tourism, etc., and also significantly save time for users . The latter is achieved due to the ability to fly outside the schedule, the ability to use small airfields for takeoff and landing, and the user does not waste time on issuing and registering air tickets and has a choice direct route to the destination. As a rule, GA aircraft are aircraft with a takeoff weight of up to 8,6 m. However, it is also possible to use a larger aircraft.
Depending on the purpose, two main groups of aircraft can be distinguished, regardless of the operating conditions - multi-purpose and specialized aircraft.
Multi-purpose aircraft are designed to solve a wide range of tasks. This is achieved by refitting and refitting the aircraft for a specific mission with little or no design changes. Depending on the ability to take off and land not only on airfields with artificial surface, but also to use the water surface for these purposes, multi-purpose aircraft can be ground-based and amphibious.
Specialized aircraft, focused on the performance of any one task.
The classification of aircraft is possible depending on the characteristics of the aerodynamic configuration, which is understood as a certain system of bearing surfaces of the aircraft. In the system of bearing surfaces there are main surfaces - wings, which create the main part of the aerodynamic lift, and auxiliary surfaces - plumage, designed to stabilize the aircraft and control its flight. There are the following types of aerodynamic schemes, in accordance with Figure 2.10.
Figure 2.10 - Aircraft aerodynamic schemes
Aircraft, according to individual features of the aerodynamic scheme, are classified primarily by the design characteristics of the wing, in accordance with Figure 2.11.
It is also possible to classify aircraft according to the fuselage scheme - depending on the type of power elements, depending on the design characteristics of the chassis - which are distinguished by the location of the landing gear, by the power plant - depending on the type of engine, the number of engines and their location.
Figure 2.11 - Structural characteristics of an aircraft wing
Of particular importance for civil aviation is the classification of aircraft depending on their flight range, in accordance with Figure 2.12:
Short-haul (main airlines) aircraft, with a flight range of - 1000-2500 km;
Medium-haul aircraft, with a flight range of - 2500-6000 km;
Long-range main aircraft, with a flight range of over 6000 km.
Figure 2.12 - Classification of aircraft
depending on range zones
· equipping passenger seats with comfortable chairs, removable tables, individual lighting, ventilation and alarm systems;
· good soundproofing of cabins;
· performance of flights at heights where "chatter" is less possible;
· equipment of passenger cabins with buffets, wardrobes, toilets and other household premises.
Special requirements apply to cargo aircraft. These requirements include:
· big loading capacity, the increased sizes of cargo compartments;
Availability of means of fastening (mooring) of goods;
Availability of intra-aircraft means of mechanization of loading and unloading.
Many of these requirements are in conflict with each other: the improvement of some characteristics entails the deterioration of others. For example, an increase in maximum flight speed causes an increase in landing speed and a deterioration in its maneuverability; compliance with the requirements of strength, rigidity and survivability is in conflict with the requirement to ensure the minimum mass of the structure; an increase in flight range is achieved by reducing the mass of the transported cargo, etc. The impossibility of simultaneously fulfilling conflicting requirements makes it impossible to create a universal aircraft or helicopter. Each aircraft or helicopter is designed to perform specific tasks.
3.2. Classification of aircraft, helicopters and aircraft engines
3.2.1. Aircraft classification
The variety of aircraft types and their use in the national economy necessitated their classification according to various criteria.
Among the many features by which an aircraft can be classified, the most important is the purpose. This feature determines the choice of flight performance, the size and layout of the aircraft, the composition of the equipment on it, etc.
The main purpose of civil aircraft is the transportation of passengers, mail and cargo, the performance of various national economic tasks. In accordance with this, according to their purpose, aircraft are divided into: transport, special-purpose and training. In its turn, transport aircraft divided into passenger and cargo. According to the maximum takeoff weight, aircraft are divided into classes, Table. 3.1.
Table 3.1
Aircraft classes
aircraft type |
||
75 and over | Il-96, Il-86, Il-76T, Il-62, Tu-154, Tu-204 |
|
An-12, Il-18, Il-114, Tu-134, Yak-42 |
||
An-24, An-26, An-30, Il-14, Yak-40 |
||
An-2, L-410, M-15 |
Training aircraft serve for the training and training of flight personnel in various educational institutions of civil aviation.
Aircraft for special purposes: agricultural, sanitary, for the protection of forests from fires and pests, for aerial photography, etc.
According to the flight range, aircraft are divided into main long-range (over 6000 km), main medium (from 2500 to 6000 km), main short-range (from 1000 to 2500 km) and aircraft of local airlines (up to 1000 km).
Cargo aircraft, in contrast to passenger aircraft, have large internal volumes in the fuselage, which make it possible to place various cargoes, a stronger floor, and are equipped with means of mechanized loading and unloading operations.
The classification of aircraft is shown in fig. 3.1. From the whole variety of design features, the main ones are singled out: the number and location of wings; fuselage type; type of engines, their number and location; chassis type; plumage type and location.
Rice. 3.1. Aircraft classification
Consider the features of aircraft schemes, due to the number and arrangement of wings.
According to the number of wings, aircraft are divided into monoplanes, that is, aircraft with one wing, and biplanes, an aircraft with two wings located one above the other. The advantage of biplanes is better, compared to a monoplane, maneuverability, due to the fact that with an equal wing area, their span is smaller for a biplane. However, due to the large frontal resistance due to the presence of inter-wing struts and braces, the biplane's flight speed is low. At present, the An-2 biplane is operated in civil aviation.
Most modern aircraft are made according to the monoplane scheme.
According to the location of the wing relative to the fuselage, low-wing, medium-wing and high-wing aircraft are distinguished. Each of these schemes has its own advantages and disadvantages.
low wing- an aircraft with a lower wing relative to the fuselage. It is this scheme that has become most widespread for passenger aircraft, due to its following advantages:
· low height of the landing gear, which reduces their weight, simplifies cleaning and reduces the volume of compartments to accommodate the chassis;
ease of maintenance of aircraft engines when placed on the wing;
· at emergency landing good buoyancy is provided on water;
· during an emergency landing with the landing gear not extended, the landing occurs on the wing, which creates less danger for passengers and crew.
The disadvantage of this scheme is that in the area of the junction of the wing and the fuselage, the smoothness of the air cutoff is disturbed and additional resistance arises, called interference, and due to the mutual influence of the wing on the fuselage. In addition, in a low wing it is difficult to protect the engines located on the wing and under the wing from dust and dirt from the airfield runway.
Sredneplan- an aircraft whose wing is located approximately in the middle of the height of the fuselage. The main advantage of such a scheme is the minimum aerodynamic drag.
The disadvantages of the scheme include the difficulty with the placement of passengers, cargo and equipment in the middle part of the fuselage due to the need to pass here the longitudinal power elements of the wing.
Vysokoplan An aircraft whose wing is attached to the top of the fuselage.
High-wing main advantages:
low interference between the wing and the fuselage;
placement of engines high from the surface of the runway. Which reduces the likelihood of damage when taxiing on the ground;
· good review lower hemisphere;
· the possibility of maximum use of the internal volumes of the fuselage, equipping it with means of mechanization of loading and unloading bulky cargo.
The disadvantages of the scheme include:
Difficulty in retracting the landing gear into the wing;
the complexity of servicing engines located on the wing;
· the need to strengthen the structure of the lower part of the fuselage.
· According to the type of fuselage, aircraft are divided into single-body, twin-boom with a gondola and "flying wing".
Most modern aircraft have a single fuselage to which the wing and tail are attached.
Depending on the type and location of the plumage, there are three main schemes:
· rear arrangement of plumage;
front plumage (plane type "duck");
tailless aircraft of the "flying wing" type.
Most modern civil aircraft are made according to the scheme with a tail unit. This scheme has the following varieties:
· the central location of the vertical keel and the horizontal location of the stabilizer;
spaced vertical plumage;
V - shaped plumage without a vertical keel.
According to the type of chassis, aircraft are divided into land and seaplanes. The landing gear of land aircraft is usually wheeled, sometimes skiing, while seaplanes are boat or float.
Aircraft are also distinguished by the type, number and location of engines. On modern aircraft, piston (PD), turboprop (TVD) and turbojet (TRD) engines are used.
The location of the engines on the aircraft depends on their type, number, dimensions and purpose of the aircraft.
In multi-engine aircraft, propeller engines are installed in nacelles in front of the wing.
Turbojet engines are most often located on pylons under the wing or in the rear fuselage.
Advantages of the first method: direct placement of engines in the air flow, unloading of the wing from bending and torque moments, ease of maintenance of the engines. However, the location of the engines close to the ground is associated with the risk of foreign objects falling into them from the runway surface. Aircraft with this arrangement of engines also create difficulties in piloting with one failed engine (flying with asymmetric thrust).
In the second method, the main advantages are the following:
The wing, clean from add-ons, has the best aerodynamic characteristics (there is more space to accommodate means of wing mechanization);
· there are no difficulties when flying with asymmetric thrust;
Reduced noise level in aircraft cabins;
The wing protects the engines from dirt when the aircraft moves along the ground;
Provides convenient maintenance of engines.
However, this arrangement of engines has serious drawbacks:
· the horizontal plumage must be moved up and the keel strengthened;
· the fuselage in the engine area must be strengthened;
· the alignment of the aircraft as the fuel burns out moves back, reducing the stability of the aircraft.
3.2.2. Helicopter classification
Helicopters are classified according to various criteria, for example, according to the maximum take-off weight (Table 3.2), according to the type of main rotor drive, the number and location of the main rotors, or the method of compensating the reaction moment of these propellers.
Table 3.2
Helicopter classes
Maximum takeoff weight, t | Helicopter type |
|
10 or more | Mi-6, Mi-10K, Mi-26 |
|
Mi-4, Mi-8, Ka-32 |
||
Ka-15, Ka-18 |
In most modern helicopters, the main rotor is driven through the transmission from the engines. During rotation, the main rotor experiences the action of the reactive moment Mreact, which is the reaction of air and is equal to Mcr - the torque on the shaft of the main rotor. This moment tends to rotate the helicopter fuselage in the direction opposite to the rotation of the propeller. The method of balancing the reactive torque of the propeller mainly determines the scheme of the helicopter.
The single-rotor helicopter scheme is currently the most common. Helicopters of this scheme have a tail rotor, which is carried out on a long tail boom beyond the plane of rotation of the main rotor. The thrust generated by the tail rotor makes it possible to balance the reactive torque of the main rotor. By changing the value of the tail rotor thrust, it is possible to carry out directional control, that is, the rotation of the helicopter about the vertical axis.
Single-rotor helicopters are simpler to manufacture and operate than others and therefore make it possible to obtain a relatively lower cost of a flight hour. Such helicopters are compact, have few parts protruding into the flow and allow you to achieve higher flight speeds than with other schemes. Sometimes a wing can be installed on such helicopters to increase speed. When approaching at a horizontal speed, a lifting force is created on the wing, as a result of which the main rotor is partially unloaded.
The cost of power (8 ... 10%) of the engine to drive the tail rotor, as well as the presence of a long tail boom and a large diameter main rotor, which increase the dimensions of the helicopter, are the disadvantages of this scheme.
In twin-rotor helicopters, reactive torque balancing is achieved by communicating counter-rotating propellers. Twin-rotor helicopters can have different rotor arrangements.
With a coaxial scheme, the shaft of the upper rotor passes through the hollow shaft of the lower one. The planes of rotation of the propellers are separated from each other by such a distance as to exclude a collision between the blades of the upper and lower propellers in all flight modes.
Coaxial helicopter directional control is provided by setting the blades of the upper and lower propellers at different angles of attack. The resulting torque difference on the rotors causes the helicopter to turn in the desired direction. Sometimes, to improve directional control, such helicopters are equipped with rudders, the action of which is similar to the action of similar rudders on an airplane. Longitudinal and transverse control is carried out by simultaneous inclination of the planes of rotation of both rotors.
Helicopters with coaxial propellers are the most compact and maneuverable, have a high weight return. However, the complexity of the design increases the cost of their production and causes difficulties in operation, especially in adjusting the carrier system.
With a longitudinal scheme, the rotors are installed at the ends of the fuselage. The counter-rotating propellers are synchronized so that the blades of one propeller always pass between the blades of the other during rotation.
The advantage of helicopters of this scheme is a long, capacious fuselage, inside which large-sized cargo can be transported. Otherwise, they are inferior to single-rotor helicopters.
Helicopters of the transverse scheme have two rotors located in the same plane on the sides of the fuselage and rotating in opposite directions. From the point of view of aerodynamics, such a layout of the rotors is the most appropriate, but the wings, which take the load from the rotors, significantly increase the weight of the helicopter structure.
3.2.3. Aircraft engine classification
The power plant is designed to create traction. It includes engines, propellers, engine nacelles, fuel and oil systems, engine and propeller control systems, etc.
Depending on the design scheme and the nature of the working process, engines are classified into piston (PD) and gas turbine (GTE). In turn, gas turbine engines are divided into: turbojet (TRD), turboprop (TVD), bypass turbojet (DTRD) and turbo-fan, fig. 3.2.
Rice. 3.2. Aircraft engine classification
TRDs are lightweight, compact and reliable, and therefore occupy a dominant position on long-haul aircraft.
HPTs have a higher fuel efficiency compared to turbojet ones, but their design is significantly heavier and complicated by a propeller, which also causes additional noise and vibration. TVD is installed on the wing and in the forward part of the fuselage. The presence of a propeller on a theater restricts other options for their location on the aircraft.
The turbojet engine is installed on the wing, under the wing on pylons, inside the fuselage, along its sides in the tail section. Each layout has its advantages and disadvantages and is selected taking into account the type and number of engines, aerodynamic, strength, mass and other features of the aircraft, and their operating conditions.
Piston engines run on aviation gasoline grades B-70 and B-95/130. The thermal energy of the fuel burned in the cylinders is converted into mechanical energy and transferred to the propeller, which creates the thrust necessary for flight. Gas turbine engines run on aviation kerosene grades T-1, TS-1, RT-1, etc.
Questions for self-control
1. What is “flight safety” and how is it ensured?
2. What achieves "economy of operation"?
3. In what areas is “passenger comfort” ensured?
4. By what signs and criteria are aircraft classified? Disadvantages and advantages of various aircraft design schemes.
5. Classification of helicopters. What are the advantages and disadvantages of various helicopter designs?
6. Give the classification of aircraft engines.
CHAPTER 4
AERODYNAMIC PERFORMANCE
AIRCRAFT
Aerohydromechanics (fluid and gas mechanics) is a science that studies the laws of motion and equilibrium of liquids and gases and their force interaction with streamlined bodies and boundary surfaces. Fluid mechanics is called hydromechanics, mechanics of a gaseous body - aeromechanics.
The development of aeronautics, aviation, and rocket science aroused particular interest in the study of the force interaction of air and other gaseous media with bodies moving in them (aircraft wing, fuselage, propeller, airship, rockets, etc.).
The design and calculation of aircraft (helicopters) are based on the results obtained from aerodynamic studies. Taking into account aerodynamics, it is possible to choose a rational external shape of the aircraft (taking into account the mutual influence of its parts) and establish permissible deviations in the external shape, dimensions, etc. during production.
For the aerodynamic calculation of an aircraft, i.e., to determine the possible range of speeds, altitude and flight range, as well as to determine such characteristics as the stability and controllability of the aircraft, it is necessary to know the forces and moments acting on the aircraft in flight. To calculate the aircraft for strength, reliability and durability, it is necessary to know the magnitude and distribution of aerodynamic forces over the surface of the aircraft. The answer to these questions is aerodynamics.
It is very important to determine the aerodynamic characteristics of the aircraft and its parts when flying with supersonic speeds, since in this case there arises an additional problem of determining the temperature on the surface of the streamlined body and heat exchange between the body and the medium.
Aerodynamics plays an important role not only in the design and calculation of an aircraft (helicopter), but also in its flight tests. With the help of aerodynamic data and flight tests, the permissible values of deformations, speeds for the aircraft, as well as flight modes, in which vibrations, shaking of the aircraft, etc. take place.
According to the principle of mechanical interaction of several moving bodies, the forces acting on the bodies depend on their relative motion. The essence of relative motion is as follows: if in a stationary air medium a body (for example, an airplane in the air) moves in a straight line and uniformly with a speed V∞, then when the medium and the airplane are simultaneously given a reverse speed V∞, the so-called “reversed” motion is obtained, i.e. i.e. an air flow runs into a stationary body (for example, an air flow in a wind tunnel onto a stationary model aircraft), while the undisturbed flow velocity is equal to V∞. In both cases, the equations describing the relative motion of the aircraft and air will be invariant. Thus, aerodynamic forces depend only on the relative motion of the body and air.
To determine the aerodynamic characteristics of bodies (for example, the wing, fuselage and other parts of an aircraft) streamlined by an air flow, a synthesis of theoretical and experimental methods is currently used: theoretical calculations with the introduction of experimental corrections or experimental studies taking into account theoretical corrections (for the influence variations of similarity criteria, boundary conditions, etc.). In both cases, computers are widely used for calculations and processing of experimental data. After the creation of the aircraft, the final stage is flight tests - an experiment in natural conditions. It is difficult to directly measure aerodynamic forces (as, for example, in wind tunnels) during flight tests. Aerodynamic characteristics are determined by processing the parameters of the movement of the aircraft relative to the air measured during the tests. To obtain a sufficient amount of experimental data, flights are carried out in various modes.
Aerodynamics is divided into two sections: low speed aerodynamics and high speed aerodynamics. The fundamental difference between these sections is as follows. When the gas flow velocities are small compared to the speed of sound propagation, the gas is considered practically incompressible in aerodynamic calculations, and changes in the density and temperature of the gas inside the flow are not taken into account. At speeds commensurate with the speed of sound, the phenomenon of gas compressibility cannot be neglected.
The task of aerodynamics is to determine the aerodynamic forces on which the flight data of aircraft depend.
Aerodynamics as a science develops in two directions: experimental and theoretical. Theoretical aerodynamics finds solutions by analyzing the basic laws of hydroaerodynamics. However, due to the complexity of the processes occurring when an air flow flows around bodies, the solutions in this case are approximate and require experimental verification. Experimental aerodynamic studies are carried out in wind tunnels or directly during flight tests of aircraft. Flight tests provide the most reliable results. They are carried out, as a rule, after tests in wind tunnels have been carried out.
Wind tunnels are devices in which an air flow is artificially created, blowing around the bodies under study.
On fig. 4.1 shows a diagram of a wind tunnel. Fan - 2 is driven by an electric motor - 1, which allows you to change the speed of the fan and the speed of the air flow. The air sucked in by the fan, having passed through the return channel - 4, enters through a converging nozzle - 7 into the working part - 6, where the test model is placed - 5. To lose air energy and prevent the appearance of vortices when the flow turns, guide vanes - 9 are used, and to create a uniform flow in the working area - a directing grill - 8. An expanding diffuser - 3 reduces the speed and, accordingly, increases the pressure of the air flow, which reduces the energy required to rotate the fan.
Rice. 4.1. Scheme of the wind tunnel: 1 - electric motor; 2 - fan; 3 - diffuser; 4 - return channel; 5 - tested model; 6 – working part of the wind tunnel; 7 - nozzle; 8 - straightening grating; 9 - guide vanes
An aerodynamic balance is used to determine the aerodynamic forces acting on the model being tested. The pressure at different parts of the model surface is measured through special holes connected to pressure gauges.
4.2. Characteristics of the air environment
atmosphere called the gaseous shell that surrounds the globe and rotates with it. The upper part of the atmosphere consists of ionized particles captured by the Earth's magnetic field. The atmosphere smoothly passes into outer space and it is difficult to establish its exact height. Conventionally, the height of the atmosphere is assumed to be 2500 km: at this height, the air density is close to the density of outer space. The study of the state of the atmosphere is of great interest for aviation, since the flight performance of aircraft depends on the properties of the atmosphere. Especially big influence meteorological conditions affect the flight performance of aircraft.
As altitude increases, air pressure and density decrease. Atmospheric air parameters depend on the coordinates of the place and change over time within certain limits. Solar radiation has a significant impact on the state of the atmosphere. The atmosphere is in continuous interaction with space and the earth.
The atmosphere consists of several layers: troposphere, stratosphere, chemosphere, ionosphere, mesosphere and exosphere, each of which is characterized by a different change in temperature depending on altitude.
In the troposphere, the temperature decreases with height by an average of 6.5 ° C every 1000 m. In the stratosphere, the temperature remains almost constant. In the chemosphere, a warm layer of air lies between two cold layers, so there are two temperature gradients: at the bottom, on average, +4°C per 1000 m, and at the top - 4.5°C per 1000 m. In the ionosphere, the temperature increases with height by an average of 10°C every 1000 m. In the mesosphere, the temperature decreases by an average of 3 ° C every 1000 m.
All layers are separated from each other by zones 1–2 km thick, called pauses: tropopause, stratopause, chymopause, ionopause, mesopause.
The lower layers of the atmosphere, in particular the troposphere and stratosphere, are currently of greatest interest to aviation.
Long-term observations of the state of the atmosphere in various places the globe showed that the values of temperature, pressure and air density vary depending on time and coordinates within a very wide range, which does not allow accurately predicting the state of the atmosphere at the time of flight. For example, in Siberia, the air temperature at ocean level in winter sometimes reaches 2130 K, and in summer 3030 K, i.e., during the year it changes by 900 K. In the middle latitudes, the temperature varies by about 700K. Significant fluctuations are also observed in temperature changes at different altitudes.
The range of pressure fluctuations is significant: in mid-latitudes at ocean level, it varies from 1.04 to 0.93 bar (1 bar = 105 N/m2). Accordingly, the air density also changes (within ± 10%).
The lack of certainty in the state of the atmosphere near the Earth and in the change in its state with increasing altitude creates serious difficulties in the aerodynamic calculations of the flight characteristics of aircraft, which, as already noted, depend significantly on the state of the atmosphere. The need to unify calculations related to aircraft when solving practical problems, for example, uniform calibration of various flight instruments (speed meters, machometers, etc.), recalculation of the flight characteristics of aircraft obtained in specific atmospheric conditions, on others led to the creation of conditional characteristics of the atmosphere - standards. Such characteristics were introduced in the form of a conditional standard atmosphere (SA), which has the form of a table of numerical values physical parameters atmosphere for a number of altitudes.
4.3. General information about the laws of aerodynamics
Aerodynamics gives a qualitative explanation of the nature of the occurrence of aerodynamic forces and, with the help of special equations, makes it possible to obtain their quantitative assessment.
When studying the motion of gases, one proceeds from the assumption that these media are complex with a continuous distribution of matter in space. The flow of gas (hereinafter - air) in aerodynamics is usually represented as separate elementary jets - closed contours in the form of tubes, through the side surface of which air cannot flow, Fig. 4.2. If at any point in space the speed, pressures and other characteristic quantities are constant in time, then such a movement is called steady.
Let us apply to the flow of air in a trickle the two most general laws of nature: the law of conservation of mass and the law of conservation of energy.
For the case of steady motion, the law of conservation of mass is reduced to the fact that the same air mass flows through each cross section of the stream per unit time, that is:
ρ1f1V1= ρ2f2V2=const,
where: ρ is the mass density of air in the corresponding sections of the stream;
f is the cross-sectional area of the trickle;
V is the air speed.
This equation is called the jet continuity equation.
The product ρfV is the mass flow rate per second of air passing through each cross section of the jet.
For low flow velocities (M< 0,3), когда сжимаемостью воздуха мож-но пренебречь, то есть когда ρ1 = ρ2 = const, уравнение неразрывности прини-мает вид:
f1V1= f2V2=const.
It can be seen from this equation that for M< 0,3 скорость течения в струйке обратно пропорциональна площади ее поперечного сечения.
As the speed increases, it begins to influence the change in density more and more noticeably. For example, at velocities corresponding to M > 1, an increase in velocity is possible only with an increase in the cross-sectional area of the jet.
https://pandia.ru/text/78/049/images/image012_75.gif" width="29" height="38 src=">, and the potential energy equal to the work of gravity relative to some conditional level is mgh1. In addition, the air above the first section does work by moving the air mass in front.This work is defined as the product of the pressure force P1f1 and the path V1Δτ.Thus, the energy of the air transmitted over the time Δτ through the section I-I will be:
Thus, based on the Bernoulli equation, we can conclude that in steady motion the sum of static pressure and dynamic pressure is a constant value.
Today, there are quite a few different aircraft, but not every one of them is called an airplane. This term refers to any aircraft that is designed to fly in the sky due to the power plant, which creates thrust and wings, which all the time remains motionless. It is the fixed wing that is the main characteristic of the aircraft, which distinguishes it from any other aircraft.
By itself, this term appeared back in 1857 - then the Russian pilot called the balloon so, there were no airplanes in the sense in which we use this word today. In a close to modern value, it was mentioned a few years later - in 1863. It was the article "Aeronautics", published in 1863 in the magazine "Voice". The author was the journalist Arkady Evald.
To date, there are a huge number of aircraft classifications. For example, by the number of wings, by the aerodynamic system, by the type of chassis and by speed.
In this text, we will consider one of the main typologies. Any aircraft, first of all, are divided according to their purpose. They are civilian, military and experimental. Each of these categories, in turn, is also divided into several types.
As the name implies, these are aircraft designed to carry passengers or cargo. The first flight on an aircraft of this type took place in Russia more than a hundred years ago - in 1914. The flight was made from St. Petersburg to Kyiv, and the plane was called "Ilya Muromets". There were 16 passengers on board.
Today, the most famous and frequently used airliner of our time is called the American aircraft of the Douglas DC-3 model. He first flew with passengers back in 1935. Over the past time, the aircraft has been improved, many other models, including those of Soviet aviation, were created on its basis.
Civil aircraft can be transport, training and special applications. Transport, in turn, are divided into:
- Freight - for the transportation of goods;
- Passenger - those planes that we fly;
There are many types of such vehicles. The easiest way to divide them is simply by manufacturer. In fact, the vast majority of aircraft in the world are produced by such companies:
Boeing
This is an American company that appeared a very long time ago, in 1916. Since then, it has been producing aircraft for civil aviation. The most popular model is the Boeing 737. It is this aircraft, released in 1968, that is most often used today. The very name "Boeing" has already become almost synonymous with the word airplane.
Airbus
This company is today the main competitor of the Boeing described above, although it was founded much later - in 1970. This European company, today its main office is located in France. Some models of this manufacturer are economical, which makes them a serious competitor to Boeing.
Military
Military aircraft are designed to conduct combat operations, that is, to protect against the enemy or vice versa, to attack. They are divided into some types, but in general, they can perform a variety of tasks - depending on the situation.
Bombers
This subspecies of military aircraft essentially has one task - the destruction of any ground objects from the air. This is done by dropping bombs or missiles on the target. Today there are many various models, among the most frequently used Su-24s and Su-34s.
It was in the bomber that the first passenger plane "Ilya Muromets", which was discussed above, was converted. During the First World War, the aircraft was converted and in the future it always served as a bomber.
Fighters
Unlike bombers, such aircraft are used for air combat. The name "fighter" sounds loud and menacing, but in fact such aircraft belong to defense equipment. It is for the offensive that they are almost never used. Fighters were actively used by both sides during the Second World War - the most famous models are the MiG-3 and Yak-1.
It is interesting that in the very first models of fighters, not a machine gun was installed, as today, but a revolver, so the rate of fire was much lower.
Fighter-bombers
Naturally, the two models described above were combined to obtain a universal model that combines the functions of both types. The main advantage of this variety is the ability to bomb any ground targets without cover at all. Such aircraft are very light, maneuverable and equipped with powerful weapons. The most successful models are MiG-27, Su-17, SEPECAT Jaguar.
Interceptors
In fact, this is not a completely separate class, just a subspecies of fighters. The main difference is that interceptors are designed to destroy a specific target, namely enemy bombers. They also differ slightly in structure - such models are additionally equipped with radar equipment. famous models - Su-15, Su-9 and others.
The purpose of attack aircraft is to support ground forces from the air. They were also often used simply to destroy various objects. The most popular model is called Il-2 and this aircraft is the most mass-produced in history - almost 37 thousand units were produced.
The aviation industry is developing every year. Today, civil and military pilots use models of liners of all kinds of configurations and varieties. Aircraft amaze with variety and variations of purpose. Let's briefly study the types of aircraft and their names in order to classify this type of equipment for ourselves.
In the world, there are several separate criteria by which aviation experts classify various aircraft. One of the important aspects of the systematization of technology is the function that the aircraft carries. Today, military and civilian vessels are used. Moreover, each category is divided into special groups.
In addition, it is also known separation according to the speed characteristics of the liner. Here aviators list groups of subsonic, transonic, supersonic and hypersonic models. This section of the classification is based on the definition of the acceleration of the liner relative to the speed of sound. Air technology, which is today used for scientific and military purposes, although previously similar models worked for passenger traffic.
If we talk about the method of control, then it will be possible to distinguish two main types - manned aircraft and drones. The second group has been used by the military and scientists. Such machines are widely used for space exploration.
Considering the types and purpose of aircraft, aviators will name and classification according to the design features of the device. Here we list the differences in the aerodynamic model, the number and type of wing, the shape of the tail unit, and the fuselage device. The last subgroup also includes varieties that relate to the types and mounting of the chassis.
Finally, consider and differences in the type, number and method of installing engines. Muscular, steam, air-jet, rocket, nuclear, electric motors are distinguished here. In addition, ships are equipped with internal combustion engines (piston modifications of power plants) or combine several variations. Of course, in one review it is difficult to consider in detail the complete classification of aircraft, so we will focus on brief description main categories.
Functionality of technology
As stated above, airliners are divided into two main groups: aircraft for civil and military aviation. In addition, experimental devices are distinguished here as a separate variety. Each category here involves a division into variations according to the type of purpose and functionality of the liner. Let's start with the study of aircraft that are used for "peaceful" purposes.
Civil side
We will determine in more detail what aircraft are, the names and subspecies of aircraft modifications. Here aviators talk about four variants of models. Let's list the categories as follows:
- passenger liners;
- cargo boards;
- training airbuses;
- special purpose aircraft.
Note that modifications for passenger transportation are separately divided into groups that determine the range of flights. Here they call main ships and airliners of local transportation.
Aircraft classification
- close ones, which cover distances up to 2,000 km;
- medium, capable of flying 4,000 km;
- long-range, operating flights at a distance of up to 11,000 km.
In addition, the maximum capacity indicator determines the following criteria for airliners of local lines:
- heavy aircraft with 100 or more seats;
- medium modifications that take up to 50 people on board;
- light liners carrying a maximum of 20 passengers.
Examples local line aircraft list the modifications SAAB , ERJ , Dash-8 , ATR . Interestingly, on certain types of liners of the local category, power plants of different classes are equipped. Here there are models with jet engines and aircraft with turboprop engine types.
Considering long-haul aircraft, let's call ships familiar to passengers Boeing and Airbus . Boeing planes are designed by an American corporation, and Airbus ships are designed by a European holding. Both companies compete with each other, constantly developing and modernizing the liners. So, today the Airbus A380 is considered the heaviest aircraft, although until the release of such a modification, American developments and 747 800 .
Model 747s are the first wide-body class aircraft that are still in service today. In addition, such aircraft are used by the best carriers in Russia and the world.
However, the Europeans do not lag behind the main competitor. The popularity and recognition of pilots won modifications , Airbus A300 and A350XWB. Model A300- the world's first wide-body aircraft, which is equipped with two engines. As you can see, the possible variations in the classification of liners defy description in one review. But knowing what planes are and who created them, the reader will decide on personal preferences and find out the basics of aviation.
Military aviation
Now let's briefly study the typology of the courts used by law enforcement agencies. Among these aircraft there are manned airliners and drones, modifications with various types of engines, including rocket engine subspecies. However, we will consider the division of these species according to profile criteria.
Military transport aircraft Il-76
Here, as in the civil classification, there is transport liners transporting personnel. This is IL-76,An-12, 26 and 124 . In the USA, these functions are carried by models Boeing C-17, 97 and Douglas YC-15. In addition, the military also uses auxiliary equipment- ambulance aircraft, liners for communication, spotters. However, the military development of the boards also uses several categories of vehicles that are found only here. Their list looks like this:
As you can see, the category of military aircraft is quite extensive and deserves serious study. We have only briefly described the main criteria for systematizing such a group. However, aviation experts prefer to classify aircraft using a comprehensive study that includes Full description side structures. Let's dwell on this issue.
About design features
Belonging to a particular category of the liner is determined by five features. Here, the designers talk about the number and method of attaching the wings, the type of fuselage, the location of the plumage and the type of chassis. In addition, the number, place of fixation and types of motor are important. Find out the known variations in the design of the sides.
Differences in design features - an important criterion for the systematization of airliners
If we consider the classification of the wing, then the liners are divided into polyplanes, biplanes and monoplanes. Moreover, in the last category, three more subspecies are distinguished: low-plan, medium-plan and high-plan sides. This criterion determines the relative position and fixation of the fuselage and wings. As for the fuselage typology, here aviators distinguish between single-body and two-beam modifications. There are also such varieties here: gondola, boat, carrying fuselage and combinations of these types.
Aerodynamic performance is an important classification criterion, since they affect. Here the designers call the types of normal circuit, "duck", "tailless" and "flying wing". In addition, a "tandem", "longitudinal triplane" and a convertible scheme are known.
The landing gear of airliners is systematized according to the design and method of fixing the supports. These elements are divided into roller, float, caterpillar, combined types and air-supported chassis. Engines are equipped on the wing or in the fuselage. Moreover, the liners are equipped with one engine or a large number of engines. In addition, the type of power plant also plays a decisive role in the systematization of the aircraft class.
Unmanned aerial vehicles have found application in the scientific and military spheres
Modern aviation has several types of liners, which are classified according to various criteria. 
According to their purpose, aircraft are divided into civil, military and experimental aircraft. 
Aircraft classification 
Airbus A380 - a giant in the world passenger liners 
Boeing aircraft is the main competitor in the field of passenger transportation of the European holding that produces Airbuses
