How an airplane flies principle. Opening the veil

An airplane is an aircraft that has a mass greater than the mass of air, and a lifting force created according to the aerodynamic principle (throwing down part of the air due to the flow around the wing). Lift is the answer to the question of why airplanes fly. It is created by bearing surfaces (mainly wings) when moving towards the air flow of an aircraft developing speed with the help of 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 the theorem of Nikolai Egorovich Zhukovsky, an outstanding Russian scientist, the founder of aerodynamics, which was formulated back 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.

In order for the lifting force to be able to lift a modern aircraft into the air, even weighing tens of tons, its wing must have sufficient area. The lift force of a wing is affected by many parameters, such as profile, area, wing planform, angle of attack, speed and airflow density. Each aircraft has its own minimum speed at which it can take off and fly without falling. Thus, the minimum speed of modern passenger aircraft is in the range of 180 to 250 km/h.

Why do planes fly at different speeds?

The size of the aircraft depends on the required speed of the aircraft. The area of ​​the wings of slow transport aircraft must be large enough, since the lift force of the wing and the speed developed by the aircraft are directly proportional. The large area of ​​the wings of slow aircraft is due to the fact that at sufficiently low speeds the lift force is small.

High-speed aircraft tend to have much smaller wings, while still providing sufficient lift. The lower the air density, the lower the wing lift becomes, therefore, at high altitude, the speed of the aircraft must be higher than when flying at low altitude.

Why do planes fly so high?

The flight altitude of modern jet aircraft is in the range 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 supply of air 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.

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.

Some researchers had crazy ideas - they wanted to fly, but why was the result so deplorable? For a long time there have been attempts to attach wings to oneself, and, waving them, fly up into the sky like birds. It turned out that human strength is not enough to lift oneself on flapping wings.

The first folk craftsmen were naturalists from China. Information about them is recorded in the "Tsan-han-shu" in the first century AD. Further, history is replete with cases of this kind, which occurred in Europe, and in Asia, and in Russia.

The first scientific justification for the process of flight was given by Leonardo da Vinci in 1505. He noticed that birds do not have to wave, they can stay in still air. From this, the scientist concluded that flight is possible when the wings move relative to the air, i.e. when they flap their wings in the absence of wind or when with fixed wings.

Why is the plane flying?

The lifting force, which acts only at high speeds, helps to keep it in the air. The special contraction of the wing allows you to create lift. The air that moves above and below the wing undergoes changes. Above the wing it is sparse, and under the wing -. Two air streams directed vertically are created. The lower flow raises the wings, i.e. plane while the top pushes up. Thus, it turns out that at high speeds the air under the aircraft becomes solid.

This is how vertical motion is realized, but what makes the plane move horizontally? - Engines! Propellers, as it were, drill a path in the airspace, overcoming air resistance.

Thus, the lifting force overcomes the force of attraction, and the traction force overcomes the braking force, and the plane flies.

Physical phenomena underlying flight control

In an airplane, everything is based on the balance of lift and gravity. The plane is flying straight ahead. Increasing the flight speed will increase the lift force, the aircraft will rise. To neutralize this effect, the pilot must lower the nose of the aircraft.

Reducing the speed will have the exact opposite effect, and the pilot will need to raise the nose of the aircraft. If this is not done, a crash will occur. Due to the above features, there is a risk of crashing when the aircraft loses altitude. If it happens close to the ground, the risk is almost 100%. If this happens high above the ground, the pilot will have time to increase speed and gain altitude.

Mankind has long been interested in the question of how it happens that a multi-ton aircraft easily rises to heaven. How does takeoff take place and how do planes fly? When an airliner moves at high speed along the runway, the wings develop lift and work from the bottom up.

When the aircraft moves, a pressure difference is generated between the lower and upper sides of the wing, which results in a lift force that keeps the aircraft in the air. Those. high air pressure from below pushes the wing up, while low air pressure from above pulls the wing towards itself. As a result, the wing rises.

To take off an airliner, it needs a sufficient takeoff run. Wing lift increases as speed increases., which should exceed the takeoff limit. Then the pilot increases the angle of takeoff, pulling the steering wheel towards you. The bow of the liner rises up, and the car rises into the air.

Then retractable landing gear and exhaust lights. In order to reduce the wing lift, the pilot gradually retracts the mechanization. When the airliner reaches the required level, the pilot sets standard pressure, and engines - nominal mode. To see how the plane takes off, we suggest watching the video at the end of the article.

The ship takes off at an angle. From a practical point of view, this can be explained as follows. The elevator is a movable surface, by controlling which you can cause the aircraft to deviate in pitch.

The elevator can control the pitch angle, i.e. change the rate of climb or loss of altitude. This is due to a change in the angle of attack and lift force. By increasing the speed of the engine, the propeller starts spinning faster and lifts the airliner up. Conversely, by directing the elevators down, the nose of the aircraft goes down, while the engine speed should be reduced.

The tail section of an airliner equipped with a rudder and brakes on both sides of the wheels.

How do airliners fly

When answering the question why planes fly, one should remember the law of physics. The pressure difference affects the lift force of the wing.

The flow rate will be greater if the air pressure is low and vice versa.

Therefore, if the speed of an airliner is high, then its wings acquire lift, which pushes the aircraft.

Some circumstances also influence the lifting force of an airliner's wing: the angle of attack, the speed and density of the air flow, the area, profile and shape of the wing.

Modern liners have minimum speed from 180 to 250 km/h, at which takeoff is carried out, plans in the sky and does not fall.

Flight altitude

What is the maximum and safe altitude of the aircraft.

Not all ships have the same flight altitude, "air ceiling" can fluctuate at height from 5000 to 12100 meters. At high altitudes, the air density is minimal, while the liner achieves the lowest air resistance.

The engine of the liner needs a fixed amount of air for combustion, because the engine will not create the necessary thrust. Also, when flying at high altitude, the aircraft saves fuel up to 80%, in contrast to the altitude up to a kilometer.

What keeps the plane in the air

To answer why airplanes fly, it is necessary to analyze in turn the principles of its movement in the air. A jet airliner with passengers on board reaches several tons, but at the same time, it easily takes off and carries out a thousand-kilometer flight.

The movement in the air is also affected by the dynamic properties of the apparatus, the design of the units that form the flight configuration.

Forces affecting the movement of an aircraft in the air

The operation of an airliner begins with the engine starting. Small craft are powered by piston engines that turn propellers to create thrust to help the aircraft move through the air.

Large airliners are powered by jet engines, which emit a lot of air during operation, while the jet force propels the aircraft forward.

Why does an airplane take off and stay in the air for a long time? Because the shape of the wings has a different configuration: rounded on top and flat on the bottom, then the air flow on both sides is not the same. On top of the wings, the air glides and becomes rarefied, and its pressure is less than the air below the wing. Therefore, through uneven air pressure and the shape of the wings, a force arises that leads to the takeoff of the aircraft upwards.

But in order for an airliner to easily take off from the ground, it needs to take off at high speed along the runway.

From this follows the conclusion that in order for an airliner to be unhindered in flight, it needs moving air, which cuts through the wings and creates lift.

Airplane takeoff and speed

Many passengers are interested in the question, what speed does the plane develop during takeoff? There is a misconception that the takeoff speed for each aircraft is the same. To answer the question, what is the speed of the aircraft during takeoff, you should pay attention to important factors.

1. The airliner does not have a strictly fixed speed. The lifting force of an air liner depends on its mass and the length of the wings.. Takeoff is performed when a lift force is created in the oncoming flow, which is much greater than the mass of the aircraft. Therefore, the takeoff and speed of the aircraft depends on wind direction, atmospheric pressure, humidity, precipitation, runway length and condition.
2. To create lift and successfully lift off the ground, the aircraft needs to gain maximum takeoff speed and sufficient takeoff run. This requires long runways. The larger the aircraft, the longer the runway required.
3. Each aircraft has its own scale of takeoff speeds, because they all have their own purpose: passenger, sport, cargo. The lighter the aircraft, the lower the takeoff speed and vice versa.

Boeing 737 passenger jet takeoff

• The takeoff run of an airliner on the runway begins when the engine will reach 800 rpm per minute, the pilot slowly releases the brakes and holds the control stick at neutral. The aircraft then continues on three wheels;
• Before taking off from the ground the speed of the liner should reach 180 km per hour. Then the pilot pulls the lever, which leads to the deflection of the flaps - flaps and raising the nose of the aircraft. Further acceleration is carried out on two wheels;
• After, with a raised bow, the airliner accelerates on two wheels to 220 km per hour, and then take off from the ground.

Therefore, if you want to know in more detail how the plane takes off, to what height and at what speed, we offer you this information in our article. We hope you enjoy your air travel.

Man will fly, relying not on the strength of his muscles, but on the strength of his mind.
N. E. Zhukovsky

Photo by I. Dmitriev.

Rice. 1. When a flat plate interacts with an air flow, a lifting force and a drag force arise.

Rice. 2. When air flows around a curved wing, the pressure on its lower surface will be higher than on the upper one. The difference in pressure gives lift.

Rice. 3. Rejecting the control stick, the pilot changes the shape of the elevator (1-3) and wings (4-6).

Rice. 4. The rudder is deflected by the pedals.

Have you ever flown? Not on a plane, not in a helicopter, not in a balloon, but themselves - like a bird? Didn't have to? And I didn't get to. However, as far as I know, no one has succeeded.

Why couldn’t a person do this, because it seems that you just need to copy the wings of a bird, attach them to your hands and, imitating birds, soar into the sky. But it was not there. It turned out that a person does not have enough strength to lift himself into the air on flapping wings. The chronicles of all peoples are full of stories about such attempts, from ancient Chinese and Arab (the first mention is in the Chinese chronicle "Tsanhanshu", written back in the 1st century AD) to European and Russian. Masters in different countries used mica, thin rods, leather, feathers to make wings, but no one managed to fly.

In 1505, the great Leonardo da Vinci wrote: “... when a bird is in the wind, it can stay in it without flapping its wings, because the same role that a wing performs in relation to air in stationary air is performed by moving air in relation to wings with stationary wings ". It sounds complicated, but in fact it is not only true, but ingenious. From this idea follows: to fly, you do not need to flap your wings, you need to make them move relative to the air. And for this, the wing just needs to report the horizontal speed. From the interaction of the wing with the air, lift will arise, and as soon as its value is greater than the weight of the wing itself and everything connected with it, the flight will begin. The matter remained small: to make a suitable wing and be able to accelerate it to the required speed.

But again the question arose: what shape should the wing be? The first experiments were carried out with flat wings. Look at the diagram (fig. 1). If an incoming air flow acts on a flat plate at a small angle, then a lifting force and a drag force arise. The resistance force tries to "blow" the plate back, and the lifting force tries to raise it. The angle at which the air blows on the wing is called the angle of attack. The greater the angle of attack, that is, the steeper the plate is inclined to the flow, the greater the lifting force, but the resistance force also increases.

Back in the 80s of the XIX century, scientists found that the optimal angle of attack for a flat wing lies in the range from 2 to 9 degrees. If the angle is made smaller, the resistance will be small, but the lifting force will also be small. If you turn steeper towards the stream, the resistance will be so great that the wing will turn more into a sail. The ratio of the lift force to the drag force is called the lift-to-drag ratio. This is one of the most important criteria related to an aircraft. It is understandable, because the higher the aerodynamic quality, the less energy the aircraft spends to overcome air resistance.

Let's go back to the wing. Observant people noticed a long time ago that birds have wings that are not flat. All in the same 1880s, the English physicist Horatio Phillips conducted experiments in a wind tunnel of his own design and proved that the aerodynamic quality of a convex plate is much greater than that of a flat one. There was also a fairly simple explanation for this fact.

Imagine that you managed to make a wing whose bottom surface is flat and the top is convex. (It is very easy to glue a model of such a wing from a regular sheet of paper.) Now let's look at the second diagram (Fig. 2). The air flow on the leading edge of the wing is divided into two parts: one flows around the wing from below, the other - from above. Please note that the air has to travel a little more from above than from below, therefore, the air speed from above will also be slightly greater than from below, right? But physicists know that as the speed increases, the pressure in the gas flow decreases. See what happens: the air pressure under the wing is higher than above it! The pressure difference is directed upwards, that's the lifting force. And if you add the angle of attack, then the lifting force will increase even more.

One of the first concave wings was made by the talented German engineer Otto Lilienthal. He built 12 models of gliders and made about a thousand flights on them. On August 10, 1896, during a flight to Berlin, his glider was turned over by a sudden gust of wind and the brave explorer pilot died. The theoretical substantiation of the soaring of birds, continued by our great compatriot Nikolai Yegorovich Zhukovsky, determined the entire further development of aviation.

And now let's try to figure out how the lift force can be changed and used to control the aircraft. All modern aircraft wings are made of several elements. The main part of the wing is fixed relative to the fuselage, and small additional flaps are installed on the trailing edge. In flight, they continue the profile of the wing, and on takeoff, during landing or during maneuvers in the air, they can deviate downward. In this case, the lifting force of the wing increases. The same small additional rotary wings are on the vertical tail (this is the rudder) and on the horizontal tail (this is the elevator). If such an additional part is rejected, then the shape of the wing or plumage changes, and its lifting force changes. Let's look at the third diagram (Fig. 3 on p. 83). In the general case, the lift force increases in the direction opposite to the deflection of the steering surface.

I will tell you in the most general terms how the aircraft is controlled. To climb up, you need to slightly lower the tail, then the angle of attack of the wing will increase, the plane will begin to gain altitude. To do this, the pilot must pull the steering wheel (control stick) towards himself. The elevator on the stabilizer deflects up, its lifting force decreases and the tail drops. In this case, the angle of attack of the wing increases and its lifting force increases. To dive, the pilot tilts the steering wheel forward. The elevator deflects down, the aircraft lifts its tail and begins to descend.

You can tilt the car to the right or left using the ailerons. They are located on the ends of the wings. Tilt the stick (or turn the yoke) to starboard causes the right aileron to go up and the left to go down. Accordingly, the lift on the left wing increases, and on the right falls, and the aircraft leans to the right. Well, how to tilt the plane to the left - guess for yourself.

The rudder is controlled by pedals (Fig. 4). Push the left pedal forward - the plane turns left, push the right pedal - to the right. But the machine does it "lazy". But in order for the plane to quickly turn around, you need to make several movements. Let's say you're about to turn left. To do this, roll the machine to the left (turn the steering wheel or tilt the control stick) and at the same time press the left pedal and take the steering wheel.

That, in fact, is all. You may ask why pilots are taught to fly for several years? Yes, because everything is just on paper. So you gave the plane a roll, took the handle on yourself, and the plane suddenly began to move sideways, as if on a slippery hill. Why? What to do? Or, in level flight, you decided to climb higher, took the helm, and the plane suddenly, instead of climbing to a height, pecked with its nose and flew down in a spiral, as they say, went into a “corkscrew”.

The pilot in flight needs to monitor the operation of the engines, the direction and altitude, the weather and passengers, their own course and the courses of other aircraft, and many other important parameters. The pilot must know the theory of flight, the location and operation of the controls, must be attentive and courageous, healthy, and most importantly, love to fly.