Why an airplane flies or why wings are needed. Why do planes fly

Why do birds fly?

The wing of a bird is designed in such a way that it creates a force that counteracts the force of gravity. After all, the bird's wing is not flat, like a board, but arched . This means that the jet of air enveloping the wing must travel a longer distance along the upper side than along the concave lower side. For both air streams to reach the wing tip at the same time, the air stream above the wing must move faster than under the wing. Therefore, the speed of air flow over the wing increases, and the pressure decreases.

The difference in pressure under the wing and above it creates a lifting force directed upward and counteracting the force of gravity.

For someone it is important now, for someone later - buy a cheap air ticket online. It is possible here! (Click on the picture!)

Entering the site, set the direction, date of departure (arrival), set the number of tickets and the computer will automatically give you a table with flights for this date and for the next flights, options, their cost.
You need to book a ticket, if possible, as early as possible and redeem it quickly while the reservation is valid. Otherwise, cheap tickets will "float away". You can find all the details, find out popular destinations from Ukraine, order air and railway tickets from anywhere to anywhere by clicking on the indicated picture - on the website at http://711.ua/cheap-flights/.

Airplanes are very complex devices, sometimes frightening with their complexity to ordinary people, people who are not familiar with aerodynamics.

The mass of modern air liners can reach 400 tons, but they calmly stay in the air, move quickly and can cross great distances.

Why is the plane flying?

Because he, like a bird, has a wing!

If the engine fails - it's okay, the plane will fly on the second. If both engines failed, history knows cases that in such circumstances they landed. Chassis? Nothing prevents the plane from landing on its belly; subject to certain fire safety measures, it will not even catch fire. But an airplane can never fly without a wing. Because that's what creates lift.

Airplanes continuously "run into" the air with their wings set at a slight angle to the airflow velocity vector. This angle in aerodynamics is called the "angle of attack". The "angle of attack" is the angle of the wing to the invisible and abstract "flow velocity vector". (see fig 1)

Science says that an airplane flies because a zone of increased pressure is created on the lower surface of the wing, due to which an aerodynamic force arises on the wing, directed upwards perpendicular to the wing. For the convenience of understanding the flight process, this force is decomposed according to the rules of vector algebra into two components: the aerodynamic drag force X

(it is directed along the air flow) and lift Y (perpendicular to the air velocity vector). (see fig 2)

When creating an aircraft, great attention is paid to the wing, because the safety of flight performance will depend on it. Looking out the window, the passenger notices that it is bent and is about to break. Do not be afraid, it can withstand just enormous loads.

In flight and on the ground, the aircraft's wing is "clean", it has minimal air resistance and sufficient lift to keep the aircraft flying at high speeds.

But when it comes time to take off or land, the plane needs to fly as slowly as possible so that lift on one side does not disappear, and on the other, the wheels can withstand touching the ground. For this, the wing area is increased: flaps(planes at the back) and slats(in front of the wing).

If you need to further reduce the speed, then in the upper part of the wing are issued spoilers, which act as an air brake and reduce lift.

The plane becomes like a bristling beast slowly approaching the ground.

Together: flaps, slats and spoilers- called mechanization of the wing. Mechanization is released by pilots manually from the cockpit before takeoff or landing.

As a rule, a hydraulic system (rarely an electric one) is involved in this process. The mechanism looks very interesting, and at the same time is very reliable.

On the wing there are rudders (according to aviation ailerons), similar to those of a ship (no wonder the plane is called an aircraft), which deviate, tilting the plane in the right direction. Usually they deflect synchronously on the left and right side.

Also on the wing are navigation lights , which are designed to ensure that from the side (from the ground or another aircraft) it is always visible in which direction the aircraft is flying. The fact is that the left is always red, and the right is green. Sometimes white "flashing lights" are placed next to them, which are very clearly visible at night.

Most of the characteristics of an aircraft directly depend on the wing, its aerodynamic quality and other parameters. Fuel tanks are located inside the wing (the maximum amount of refueling fuel depends very much on the size of the wing), electric heaters are placed on the leading edge so that ice does not grow there in the rain, landing gear is attached to the root part ...

Aircraft speed reached using a power plant or turbine. Due to the power plant, which creates traction force, the aircraft is able to overcome air resistance.

Planes fly according to the laws of physics.

Aerodynamics as a science is based on t theorem of Nikolai Egorovich Zhukovsky, outstanding Russian scientist, founder of aerodynamics, which was formulated in 1904. A year later, in November 1905, Zhukovsky presented his theory of creating the lift force of an aircraft wing at a meeting of the Mathematical Society.

Why do planes fly so high?

The flight altitude of modern jet aircraft is within from 5000 to 10000 meters above sea level. This is explained very simply: at such a height, the air density is much less, and, consequently, the air resistance is also less. Airplanes fly at high altitudes because when flying at an altitude of 10 kilometers, the aircraft consumes 80% less fuel than when flying at an altitude of one kilometer.

However, why then do they not fly even higher, in the upper layers of the atmosphere, where the air density is even less?

The fact is that in order to create the necessary thrust by an aircraft engine a certain minimum air supply is required. Therefore, each aircraft has a maximum safe flight altitude limit, also called the "service ceiling". For example, the practical ceiling of the Tu-154 aircraft is about 12,100 meters.

Since ancient times, watching the flight of birds, man himself wanted to learn how to fly. The desire to fly like a bird is reflected in ancient myths and legends. One such legend is that of Icarus, who made wings to fly high into the sky, closer to the radiant sun. And although the flight of Icarus ended tragically, birds fly perfectly, despite the fact that they are significantly heavier than air. Three thousand years after the origin of this legend, at the very beginning of the 20th century, the first human flight in an airplane was carried out. This flight lasted only 59 seconds, and the plane flew only 260 meters. Thus, a man's long-standing dream of flying came true. Modern aircraft fly much farther and longer. Let's try to figure out why a plane with a huge mass flies, why it can fly faster, higher and farther than any bird, why a glider without a motor can soar in the air for a long time.

Despite the fact that during the flight, unlike birds, the wings of an aircraft are rigidly fixed to the body, the aircraft flies precisely thanks to them, as well as the engines that create thrust and accelerate the aircraft to the required speed. The cross section of an airplane wing is very similar to that of a bird's wing. And this is not accidental, since when designing an airplane, people, first of all, were guided by the flight of birds. During the flight, four forces act on the wing of an aircraft: the thrust force created by the engines, the force of gravity directed towards the Earth, the force of air resistance that impedes the movement of the aircraft, and, finally, the lift force, which provides climb. The ratio of these forces determines the ability of the aircraft to fly. When flying at a constant speed, the sum of these forces must be equal to 0: the thrust force compensates for the drag force, and the lift force compensates for the force of gravity. It is important for anyone who is interested in aeromodelling to know this in order to make a reliable flying model of an aircraft.

A very important parameter is the angle of attack - the angle between the chord of the wing (the line connecting the leading and trailing edges of the wing) and the direction of the air flow around the wing. The smaller the angle of attack, the lower the drag force, but at the same time, the lower the lift force, which ensures takeoff and stable flight. Therefore, an increase in the angle of attack provides sufficient lift for takeoff and flight. Due to the asymmetry of the shape of the wing, the air above the wing moves faster than under it, and, according to the Bernoulli equation, the air pressure under the wing is greater than above it. However, the resulting lift force is not sufficient for takeoff, and the main effect is achieved due to air compaction under the wing by the oncoming flow, which essentially depends on the angle of attack of the aircraft wing. By changing the angle of attack, you can control the flight of the aircraft, this function is performed by flaps - deflected surfaces symmetrically located on the trailing edge of the wing. They are used to improve the carrying capacity of the wing during takeoff, climb, descent and landing, as well as when flying at low speeds.

The great Russian mechanic, founder of the science of aerodynamics, Nikolai Egorovich Zhukovsky, having comprehensively studied the dynamics of bird flight, discovered the law that determines the lift force of the wing. This force is determined by the pressure difference above and below the wing and is calculated using the following formula:

where is the air density, is the speed of the incoming air flow, is the area of the aircraft wings, is the speed of air circulation near the wing. The dependence of lift on the angle of attack can be obtained using the law of conservation of momentum:

A similar formula for calculating the lift force of the first aircraft in the history of mankind was used by the Wright brothers:

Where
- Smeaton's coefficient, obtained back in the 18th century. This formula is obtained from the previous one at an angle of attack equal to 45 0 . Using this formula, you can calculate the minimum speed an aircraft needs to take off:

where is the free fall acceleration, m is the mass of the aircraft.

Let's calculate the takeoff speed of the Boeing 747-300. Its mass is approximately 3 10 5 kg, and the wing area is 511 m 2. Considering that the air density is 1.2 kg/m 3 , we get a speed value of about 70 m/s or about 250 km/h. It is at this speed that modern passenger planes take off.

Using the proposed method, we suggest that you calculate the speed that a model aircraft with a mass of 5 kg and a wing area of 0.04 m 2 must have in order to take off.

The speed (V) of movement of the liners is not constant - one is needed on the rise, and another in flight.

The takeoff actually begins from the moment the vessel moves along the runway. The device accelerates, picks up the pace necessary for separation from the canvas, and only then, due to the increase in lift, soars up. The necessary V to pull off is written in the manual for each model and general instructions. The motors at this moment are working at full capacity, giving a huge load on the machine, which is why the process is considered one of the most difficult and dangerous.
To fix in space and occupy the allocated echelon, it is necessary to reach a different speed. Flight in a horizontal plane is possible only if the PS compensates for the Earth's gravity.

It is difficult to name indicators of the speed with which the aircraft is able to take off and stay there for a certain time. They depend on the characteristics of a particular machine and environmental conditions. A small single-engine V will logically be lower than that of a giant passenger ship - the larger the device, the faster it has to move.

For a Boeing 747-300, this is about 250 kilometers per hour if the air density is 1.2 kilograms per cubic meter. For Cessna 172 - about 100. Yak-40 breaks away from the canvas at 180 km / h, Tu154M - at 210. For Il 96, the average reaches 250, and for Airbus A380 - 268.

Of the conditions independent of the device model, when determining the number, they rely on:

direction and strength of the wind - the oncoming one helps by pushing the nose up
the presence of precipitation and air humidity - can complicate or contribute to acceleration
human factor - after evaluating all the parameters, the decision is made by the pilot

The speed characteristic of the echelon is referred to in the technical specifications as "cruising" - this is 80% of the maximum capabilities of the machine

The speed at the echelon itself also depends directly on the model of the ship. In the technical specifications, it is referred to as "cruising" - this is 80% of the maximum capabilities of the machine. The first passenger "Ilya Muromets" accelerated to only 105 kilometers per hour. Now the average number is 7 times higher.

If you are flying an Airbus A220, the figure is at the level of 870 km/h. A310 usually moves at a speed of 860 kilometers per hour, A320 - 840, A330 - 871, A340-500 - 881, A350 - 903, and the giant A380 - 900. The Boeings are about the same. Boeing 717 flies at cruising at 810 kilometers per hour. Mass 737 - 817-852 depending on the generation, long-haul 747 - 950, 757 - 850 km / h, the first transatlantic 767 - 851, Triple Seven - 905, and jet passenger 787 - 902. According to rumors, the company is developing a liner for civil aviation, which will deliver people from one point to another at V=5000. But so far, the top fastest in the world includes only the military:

the American supersonic F-4 Phantom II, although it has given way to more modern ones, is still in the top ten with an indicator of 2370 kilometers per hour
single-engine fighter Convair F-106 Delta Dart with 2450 km/h
combat MiG-31 - 2993
experimental E-152, whose design formed the basis of the MiG-25 - 3030
XB-70 Valkyrie prototype - 3,308
research Bell X-2 Starbuster - 3 370
The MiG-25 is capable of reaching 3492, but it is impossible to stop at this mark and not damage the engine
SR-71 Blackbird - 3540
world leader rocket-powered X-15 - 7,274

It is possible that civilian ships will someday be able to achieve these indicators. But definitely not in the near future, while the main factor in the matter remains the safety of passengers.

4 parts of an airliner that affect flight performance

Flying cars differ from ordinary ones in very complex designs that provide for every little thing. And besides the obvious details, other parts also affect the possibilities and characteristics of movement - in total, 4 main ones were collected.

1. Wing. If, in the event of an engine failure, you can fly to the nearest airfield on the second one, and in case of malfunctions in two at once, you can land with pilot experience, you will not move away from the point of departure without a wing. There will be no it - there will be no necessary lifting force. It is no coincidence that they speak of the wing in the singular. Contrary to popular belief, the aircraft has one. This concept denotes the entire plane diverging in both directions from the side.

Since this is the main part responsible for being in the air, a lot of attention is paid to its design. The form is built according to exact calculations, verified and tested. In addition, the wing is able to withstand huge loads so as not to jeopardize the main thing - the safety of people.

2. Flaps and slats. Most of the time, the wing of the aircraft has a streamlined shape, but additional surfaces appear on it during takeoff and landing. Flaps and slats are produced in order to increase the area and cope with the forces acting on the vehicle during severe loads at the beginning and end of the path. When landing, they slow down the liner, do not allow it to fall too quickly, and on the rise they help to stay in the air.

3. Spoilers. Appear on the top of the wing at times when it is required to reduce PS. They play the role of a kind of brake. This and the details from the previous paragraph are mechanization, which the pilots control manually.

4. Engine. Screw pull the car behind them, and jet "push" forward.

Even at the beginning of the last century, few people believed in the idea of creating a flying vehicle, today airplanes are not surprising to anyone. Although only a few understand the principles of their movement - the design of the vehicles, the physics of flights seem too complicated and give rise to a lot of misconceptions. But an ordinary passenger does not need to know this. The main thing to remember is that the capabilities of each model of liners are calculated, and it is possible to repeat the fate of Icarus only in rare cases.

Why do planes fly? The dream of flying has accompanied man since ancient times. It was reflected in the ancient Greek myth of Daedalus and Icarus, the drawings of several aircraft were left behind by the great Leonardo da Vinci, and Cyrano de Bergerac fantasized about outlandish ways of moving in the air.

In addition, in the history of many civilizations there are documented information about successful and not very successful attempts of desperate inventors to get off the ground. Among them are worthy of mention:

flying kites and "sky lanterns", the first prototypes of balloons, in China before the Middle Ages,
the progenitor of the hang glider, successfully tested in the Caliphate of Cordoba in the 9th century,
the first parachute based on da Vinci's sketches in early 17th century Europe,
successful glider and rocket flights in the Ottoman Empire in the 17th century.

The first officially recorded flight of a man in an aircraft was made on the air structure of the Montgolfier brothers in 1783. However, it became possible to build the first working model of an aircraft only at the beginning of the 20th century, after the industrial revolution, which seriously accelerated scientific and technological progress.

The old dream of mankind finally came true thanks to the use of an internal combustion engine as a power plant instead of an archaic steam engine that did not provide the necessary power.

Why do planes fly?

Modern aircraft are complex high-tech aircraft with a large mass or, as they say, with a mass greater than the mass of air. At the same time, they seem to easily manage to defy the law of universal gravitation and get off the ground. This is achieved thanks to the laws of aerodynamics and the two most important structural elements of the aircraft:

power point ();
wing shape.

The presence of the power plant distinguishes the aircraft from the glider, and the static wing - from the helicopter.

aircraft wing- a surface with a complex handicap determined by the requirements of aerodynamics, the main purpose of which is to create an aerodynamic lift force necessary for liftoff from the ground and further flight. The lifting force arises during the acceleration of the aircraft due to the fact that the wing, which is at an acute angle to the oncoming air masses, creates a pressure difference.

This is due to the convex shape of the wing from above: the air flow passing over it has less pressure than the flow flowing around from below. By the way, contrary to popular belief, the aircraft has only one wing. The fuselage simply divides it into two consoles: right and left.

Power plant (engine)- an energy complex responsible for creating thrust, which, overcoming the resistance of air masses, provides the aircraft with forward motion. In other words, it is the power plant during takeoff that accelerates the aircraft to a speed at which the aircraft wing begins to create lift, and maintains the necessary thrust when moving in airspace. There are three groups of aircraft engines, depending on the method of generating thrust:

screw;
reactive;
mixed type or combined.

Thus, the joint work of the wing and the power plant of the aircraft allows it to take off and move in the airspace. Of course, these two structural elements of the aircraft are not enough for a safe flight. The design of the aircraft combines many systems that serve this purpose.

Why do airplanes fly at an altitude of 10,000 meters?

According to popular belief, aircraft fly at an altitude of about 10 km. This is not entirely true, each flight has its own optimal altitude, which depends on the type of aircraft and its characteristics, the specific gravity of the aircraft and the current weather conditions.

Often, her choice is not even made by the crew of the ship, but by the dispatch service on the ground. In addition, it should be noted that in civil aeronautics, the “even-odd” rule is used: liners moving to the west, north-west and south-west adhere to an even height that is a multiple of thousands of meters (10 thousand meters), and those heading in other directions - odd ( 9 or 11 thousand meters).

The first plane of the Wright brothers took off only 3 meters, the modern lightest aircraft fly at an altitude of up to 2 kilometers, and for the latest generation fighters, the optimal height is about 20 thousand meters.

However, for most passenger liners, the ideal flight altitude is between 9 and 12 thousand meters above the surface, that is, we can really talk about 10 kilometers as the average flight altitude in civil aviation. This choice is due to several reasons:

banal savings - at a higher altitude there is less air density, less counter resistance, which means less fuel consumption;
at this altitude, the aircraft is less dependent on atmospheric phenomena;
the temperature at 10 thousand meters - about -50 degrees Celsius - is well suited for cooling jet engines of liners;
higher altitude provides more time for crew decision-making, as well as maneuvering and planning in case of an emergency on board;
at such altitudes, there is no chance of collision with flocks of birds, which can lead to an emergency situation.

Every aircraft has an altitude limit at which air pressure can create lift. Above 12 thousand meters, the air becomes too rarefied for a passenger liner with average characteristics. Engine power drops, and the volume of fuel consumption increases sharply, and the aircraft begins to "fall over".

Why don't planes fly over the poles?

In fact, cross-polar passenger flights, although their number is small, are now regularly carried out. At least air routes across the North Pole were opened in 2001, and at the moment they are successfully used by air carriers in the USA, Canada, China, Korea, Singapore, Thailand and the United Arab Emirates. However, there are two points that complicate the development of such routes:

difficulties with radar support by the dispatching service throughout the route;
insufficient technical equipment and poor air navigation services in the Siberian part of the Eurasian continent.

It is possible that further technological progress and the implementation of large-scale projects for the construction of air navigation stations in the places where routes pass will make flights through the North Pole more common.

It makes economic sense: it is estimated that cross-polar flights will eliminate transfers and reduce flight time by 25% on routes connecting North America and Asia. The South Pole, in turn, is remote from the main airways, and there are no rational reasons for regular flights to pass near it.

Why don't planes fly across the Indian Ocean?

Indeed, if you open any flight map, you will find that the route of aircraft flying over the waters of the Indian Ocean always lines up along the land, even if such a path seems to be longer.

After several air accidents in recent years, a mystical pseudo-scientific explanation for the catastrophes and disappearances of aircraft in this geographical region has begun to gain popularity. Moreover, the supporters of this theory cite the features of the aircraft flight map as proof of their innocence. Of course, the true answer is far from mystical.

Modern passenger aircraft fly in accordance with the ETOPS standards - a set of requirements for flying twin-engine aircraft over terrain without landmarks. These standards were developed by the International Civil Aviation Organization.

According to ETOPS, routes are drawn up so that the aircraft is always within the specified maximum flight time to the nearest airport where it would be possible to reach in the event of an engine failure.

Currently, the maximum interval according to these standards is 180 minutes, depending on the design, aircraft are also certified for 60 and 120 minutes of the maximum distance from the nearest airfield. That is why civil aviation routes almost do not pass through the deserted expanses of the Indian Ocean.

Why do planes fly low?

If we exclude the obvious climb and landing approach, in everyday life we often see air force aircraft, the Ministry of Emergency Situations or agricultural aircraft at low altitudes. However, there is a reason why passenger liners can fly relatively low for long periods of time. It is usually associated with the need for an unplanned landing.

In aviation, there is such a parameter as the maximum landing weight that the landing gear can withstand during landing. Usually, fuel is poured into the aircraft to cover the distance along the route with a navigation margin. If it is necessary to land the aircraft earlier than planned, when there is still a lot of fuel on board and the maximum landing weight is higher than the permissible value, excess fuel is “burned” by flying at low altitudes. If this is not done, the landing gear simply will not survive the landing.

A large jet plane - along with hundreds of passengers in it - weighs several hundred tons. How can such a huge and heavy machine, firstly, take off from the ground and, secondly, remain in the air on a path of thousands of kilometers? Airplanes operate on a complex mixture of aerodynamic principles - theories that explain the movement of air and the behavior of bodies moving through that air.

Airplanes are powered by engines. Small aircraft usually use piston engines. The piston engine turns the propellers, and the propellers provide the thrust that propels the aircraft through the air, just as a ship's propeller produces the thrust that propels the ship through the water.

Large aircraft use jet engines that are powered by burning fuel. Such engines push huge amounts of air, and the jet force makes them move forward.

Airplanes are able to take to the air and stay in the air thanks to the shape of their wings. The wing of an aircraft is flat on the bottom and rounded on top. When the thrust generated by the engine causes the aircraft to move forward, the air separates, passing the wing on both sides. Above the rounded surface of the wing, air passes faster than under the flat bottom.

The faster moving air from above becomes rarefied, its pressure becomes less than that of the air below the wing, and due to this, the wing tends to rise up. Thus, the unequal air pressure due to the shape of the aircraft's wings generates a force called lift. Thanks to this force, the plane can fly.

The force of the moving air is also used to steer the aircraft. The aircraft is controlled using ailerons (roll control) located on the wings and tail of the aircraft elevator (pitch control, i.e. descending or climbing. If they are installed at an angle, they will create an obstacle to the air flow, as a result causing the aircraft to turn or change its flight path.

In order to stay in the air, the aircraft must be in motion all the time, its wings must cut through the air to create lift. Moving air is also needed to control the aircraft.

In other words, an airplane cannot fly unless there are engines to provide thrust. And in order to get off the ground and take to the air, the plane must first rush at high speed along the ground.