Why is the plane so heavy that it can fly in the sky

Originally, humans wanted to be able to fly freely in the air like birds. Later, after repeated practice, the airplane was invented. And the plane can fly because of its wings and engines.

When the airplane is moving, the air above the wing is fast, and the air under the wing is slow, so that an upward lift is generated, and the plane will fly smoothly into the sky. In addition, the engine in the aircraft is connected to the propeller, and the propeller rotates to drive the airflow, and the aircraft can fly in the sky for a long time. (100,000 Why Nets for Elementary School Students) Why do airplanes fly?

Why do airplanes fly? Despite the cooperation of various departments, the main thing is that the aircraft has a pair of wings with a special profile shape. Wing profiles are also known as airfoils.

A typical airfoil is convex at the top and flat at the bottom, and is often referred to as streamlined. According to the continuity of the fluid and Bernoulli's theorem, the air flow through the upper surface is squeezed compared to the air far ahead, and the flow velocity accelerates and the pressure decreases, and even suction (negative pressure) is formed, and the flow velocity of the air flowing through the lower surface slows down. As a result, a pressure difference is formed between the upper and lower wing surfaces.

This pressure difference is aerodynamic. According to the law of force decomposition, it is broken down along the direction of flight into upward lift and backward resistance. The drag is overcome by the thrust provided by the engine.

The lift is just enough to overcome its own gravity and lift the aircraft into the air. That's why airplanes fly.

The wing shape of the aircraft is special, under the thrust of the engine, this wing will make the air pressure up and down the wing different, generating lift, and the lift force makes the plane fly.

The plane is big and heavy, what does it fly in the sky on? Is it the same as we think?

Airplanes are heavier-than-air aircraft, so they need to expend their own power to gain lift. And the ** of lift is the effect of air on the wing in flight.

The upper surface of the wing is curved and the lower surface is flat, so when the wing is in relative motion to the air, the air flowing through the upper surface travels a distance (s1) in the same time (t) than the air flowing through the lower surface (s2), so the relative velocity of the air on the upper surface is faster than the air on the lower surface (v1 = s1 t> v2 = s2 t1). According to Panulli's theorem – "The pressure exerted by a fluid on the surrounding matter is inversely proportional to the relative velocity of the fluid." ", so the pressure exerted by the air on the upper surface on the wing f1 is less than that on the lower surface f2 .

The resultant force of f1, f2 must be upward, which creates a lift force.

From the principle of the wing, we can also understand how the propeller works. The propeller is like a vertical wing, with the bump facing forward and the smooth facing backward. The resultant force of the pressure as it rotates forward, pushing the propeller forward, thus driving the aircraft forward.

Of course, the propeller is not simply raised and smooth, but has a complex curved surface structure. Older propellers were fixed shapes, while later designs were designed with relative angles that could be changed to improve propeller performance.

Flying requires power to move the aircraft forward, and more importantly, for the aircraft to gain lift. Early airplanes were usually powered by piston engines, and four-stroke piston engines were the mainstay. The principle of this type of engine is shown in the figure, which is mainly to inhale air, ignite and expand after mixing with fuel, drive the piston to reciprocate, and then convert it into the rotary output of the drive shaft

The cross-section of the wing of an aircraft is generally rounded and blunt at the front and sharp at the rear, with an arched upper surface and a flat lower surface. When equal mass air passes through both the upper and lower surfaces of the wing, different flow velocities are formed above and below the wing. The velocity of air passing through the upper surface of the wing is high and the pressure is small; When passing through the lower surface, the flow velocity is small and the pressure is strong, so the aircraft will have an upward resultant force, that is, the upward lift, due to the existence of lift, so that the aircraft can leave the ground and fly in the air.

The faster the aircraft flies and the larger the wing area, the greater the lift generated.

The direction of gravity is the opposite of lift, it is a downward force caused by the gravitational pull of the earth, and the magnitude of gravity is affected by the weight of the aircraft itself and the amount of fuel it carries. The pulling force causes the aircraft to fly forward in the air, and the power of the engine determines the amount of pulling force. In general, the greater the engine output, the greater the thrust generated and the faster the aircraft can fly.

When the aircraft is in the air, it is hindered by atmospheric molecules in the air, and this obstacle forms a drag force that is opposite to the direction of the pulling force, limiting the flight speed of the aircraft.

1. Aircraft flight principle:

1. The difference in pressure between the air flow produces lift: the ascent of the aircraft is based on Bernoulli's principle, that is, the greater the flow velocity of the fluid (including liquid and air), the smaller the pressure; The smaller the flow velocity, the greater the pressure. When the aircraft flies, the streamline distribution of the air around the wing is different according to the shape of the cross-section of the wing, and the upper and lower streamlines are dense and the flow velocity is large, and the streamlines below are sparse and the flow velocity is small.

From Bernoulli's equation, the pressure above the wing is small, and the pressure below is strong. This creates a lift force in the direction acting on the wing.

2. The shape of the wing of the aircraft can make the flow velocity under the wing lower than the flow rate above, resulting in the pressure difference between the upper and lower wings (that is, the pressure below is stronger than the pressure above), so there is a lift, and this pressure difference (or the magnitude of the lift) is related to the forward speed of the aircraft.

3. When the speed of the aircraft is greater, the pressure difference, that is, the lift, will also be greater. Therefore, the plane must take off at a high speed so that the plane can take to the sky. When the plane needs to descend, as long as it reduces the speed of its forward, its lift will naturally become smaller, less than the weight of the aircraft, and it will descend and land.

An aircraft powerplant is a device used to generate pull (propeller aircraft) or thrust (jet aircraft) to move an aircraft forward. The power plant with thrust vectoring can also be used for maneuvering flights. Most modern military aircraft are jets.

The power plant of jet aircraft is mainly divided into two categories: turbojet engines and turbofan engines.

Because the design in this regard is also very advanced, and it can also play a certain buoyancy in this process, even if it is heavier in this case, it can still take off.

Mainly because the plane has some stronger power, even if it is very heavy, it can still be supported, it can resist gravity, so it can fly in the sky.

Because the speed of the aircraft is very high, and the wings are also under the ailerons, a certain pressure difference will also be formed, so the aircraft will take off.

Mainly because of the configuration inside the plane and the fact that the plane was originally meant to fly into the sky, even if it was particularly heavy, it could also be made to fly into the sky according to some special principles.

The main reason is that the engine power of the aircraft is very powerful, and the aerodynamic shape of the aircraft can push the aircraft into the sky.

The reason why the aircraft can go to the sky is because the design and development of the aircraft uses the structure of the bird's wings, as well as enough kinetic energy to allow it to take to the sky.

Any aircraft must generate a lift force greater than its own gravity in order to fly into the air, which is the basic principle of aircraft flight.

I believe everyone has played with kites or bamboo dragonflies when they were children, these two small gadgets are very simple in structure, but they contain profound principles of flight.

The wings of the aircraft include fixed-wing and rotary-wing, and the principle of the kite is somewhat similar to that of a glider, which is directed by the blowing of the oncoming airflow.

, but there is a certain difference with fixed-wing aircraft; However, gyroplanes and bamboo dragonflies have the same effect, both are produced by rotor rotation.

Generate upward lift.

How does the wing generate lift? Let's start with a little experiment: hold one end of a blank piece of paper, the other end of the white paper will naturally hang down due to gravity, and now we will take the white paper to our mouth and blow horizontally to see what happens. Ha, not only was the white paper not blown open, but the hanging end floated up, what is the reason for this? The basic principles of fluid mechanics tell us that the atmospheric pressure of the slow-flowing is greater, while the atmospheric pressure of the fast-flowing atmosphere is smaller, and the air on the white paper is blown and flows faster, and the pressure is higher than that under the white paper.

The air that does not move is small, so the white paper is held up.

In the case of a fixed-wing aircraft, when it flies in the air at a certain speed, the movement of the wing relative to the air is okay according to the principle of relative motion.

It is seen as the wing is not moving, while the air flow through the wing at a certain speed. Because the wing is generally asymmetrical, the upper surface is more convex, and the lower surface is relatively flat, which makes the air be divided into upper and lower strands when flowing through the wing, the air flowing through the upper surface is fast and the pressure is small, and the air flowing through the lower surface is slow and the pressure is large, which produces a pressure difference between the upper and lower wings, and the upward pressure is the lift of the aircraft, which drags the aircraft in the air.

The plane is big and heavy, what does it fly in the sky on? Is it the same as we think?

The side profile of the wing is a shape in which the upper edge is arched upwards and the lower edge is basically straight. Therefore, the air flow blowing through the upper and lower surfaces of the wing and from the front end of the wing to the rear end at the same time will pass through the upper edge faster than the lower edge (because the upper edge has a large arc and a longer arc length, which means that the distance is longer).

According to the Bernoulli equation of physics, the same fluid flowing through a certain surface has less pressure on the surface at a faster speed. Therefore, it is concluded that the atmospheric pressure on the upper surface of the wing is smaller than that on the lower surface, so that the lift force is generated, and the lift force reaches a certain level, and the aircraft can lift off the ground.

There's a formula that I don't know if you've ever seen: l cl*1 2* *v*v*s.

Its significance is that the lift of an aircraft is the product of the following five quantities:

1.Lift coefficient cl

That c represents the coefficient, l is the corner code, I don't have a character tool can't type), its value is related to many fine variables such as the windward angle of the aircraft, generally in a few tenths, the details are not very affectionate: (

2.Half.

That's 3Atmospheric density

The environment in which the aircraft is located, which can be high altitude or low altitude).

4.The square of the airplane's velocity relative to the surrounding atmosphere.

v*v (no corner code can not be typed, can only be expressed like this).

5.Wing area.

This formula is only suitable for relatively slow flights, just like the common flight of large and small passenger aircraft, other aircraft (as long as the wings) can be used when the speed does not exceed Mach 1, but the high speed flight of Mach 2 or 3 like a fighter is not good, if the speed is too large, the air on the surface of the wing will become viscous, to take into account the Reynolds number, there is another formula at that time, it is very complicated, I don't understand. ：）

Under the premise that the aircraft's own engine or the outside world provides power (such as a catapult aircraft during takeoff), relying on the fixed (some aircraft's wings are foldable or variable angle) wings (or similar rotors of aircraft such as ***) generate lift when moving with the air, so as to realize the flight of the aircraft in the sky.

It can be said that if an aircraft wants to fly, it is closely related to the lift generated by the combination of its own power and air.

However, how to make the aircraft fly high and fly smoothly, it still comes down to the performance of the aircraft itself, such as: wings, engines, the advanced degree of various on-board electronic equipment, the overall design of the fuselage and wings, and the weight of the aircraft are all important factors affecting the performance of the aircraft.

Because it's an airplane. Oil-burning.

The earth is heavy, but it doesn't float in space!

The top of the wing is longer than the bottom, and the air takes the same time from A to B, so the air velocity above is greater than that below, and the pressure is smaller where the flow velocity is larger, and the pressure difference is upward, resulting in lift.