What does the plane fly on, and what does the plane take off

The principle of lift The aircraft is a heavier aircraft than air, so it needs to consume its own power to obtain lift And the ** of lift is the effect of the air on the wing in flight In the following diagram, there is a schematic profile of the wing 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 the 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 the 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 of the wing f1 is less than that of the lower surface f2 The resultant force of f1 and f2 must go upward, which produces lift From the principle of the wing, we can also understand the working principle of the propeller The propeller is like a vertical wing, with the bulge facing forward, Smooth backward facing The resultant force of the pressure when rotating is forward, pushing the propeller forward, thereby driving the aircraft forward Of course, the propeller is not simply convex and smooth, but has a complex curved surface structure The old propeller is a fixed shape, and the later design adopts a design such as a relative angle that can be changed to improve the performance of the propeller Power principle: turbojet engine Turbofan engine Ramjet engine Turboshaft engine Flight needs power to make the aircraft move forward, and more importantly, to make the aircraft gain lift Early airplanes usually used piston engines as power, and four-stroke piston engines were the main The principle of this type of engine is shown in the figure, which is mainly to inhale air, mix with fuel and ignite and expand, drive the piston to reciprocate, and then convert it into the rotary output of the drive shaft: The power emitted by a single piston engine is very limited, so people connect multiple piston engines in parallel to form a star or V-piston engine The picture below shows a typical star piston engine Most modern high-speed aircraft use jet engines. The principle is to suck the air in, mix it with the fuel, ignite, and spray the expanded air backwards, and its reaction force pushes the aircraft forward In the engine profile diagram of the figure below, a compressed air fan sucks in air from the air intake, and the compressed air is one by one, so that the air can better participate in the combustion The orange-red cavity behind the fan is the combustion chamber, where the mixed gas of air and oil is ignited, and the combustion expansion is sprayed backwards, pushing the last two fans to rotate, and finally discharging the engine gas, thus completing an outside The last two fans are mounted on the same bottom bracket as the front compressor fan, so the compressor fan continues to suck in the empty work cycle

The ascent of the aircraft is based on Bernoulli's principle, that is, the greater the velocity of the fluid, the less its pressure; The smaller the flow velocity, the greater the pressure.

The specific reason: because the wing is subjected to upward lift. The streamline distribution of the air around the wing when the aircraft is flying refers to the asymmetry of the shape of the wing cross-section, the streamline above the wing is dense and the flow velocity is large, and the streamline below is 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 wings, which allows the aircraft to fly.

The main function of the wing is to provide lift for the aircraft to support the aircraft to fly in the air, and also play a certain role in stability and control. Ailerons and flaps are generally installed on the wings. Manipulating the ailerons allows the aircraft to roll; Lowering the flaps increases the lift coefficient of the wing.

Classification of aircraft:

Aircraft are not only widely used in civil transportation and scientific research, but also an important part of the modern military, so they are divided into civil aircraft and military aircraft. In addition to passenger planes and transport aircraft, civil aircraft also include agricultural aircraft, forest protection aircraft, aerial survey aircraft, medical rescue aircraft, tour aircraft, business aircraft, sports aircraft, experimental research aircraft, meteorological aircraft, aerobatic performance aircraft, law enforcement aircraft, etc.

Aircraft can also be classified by the shape, number, and relative position of the components

1. According to the number of wings, it can be divided into monoplane, biplane and multiplane. According to the position of the wing relative to the fuselage, it can be divided into lower monoplane, medium monoplane and upper monoplane.

2. According to the plane shape of the wing, it can be divided into straight-wing aircraft, swept wing aircraft, forward-swept wing aircraft and delta-wing aircraft.

3. According to the position of the horizontal tail and whether there is a horizontal tail, it can be divided into normal layout aircraft (the horizontal tail is behind the wing), canard aircraft (the front fuselage is equipped with a winglet surface) and tailless aircraft (no horizontal tail); Normal layout aircraft have single vertical tail, double vertical tail, multiple vertical tail and V-tail types.

4. According to the use, it can be divided into fighters, bombers, attack aircraft, and interceptors. According to the type of propulsion device, it can be divided into propeller aircraft and jet aircraft;

5. According to the type of engine, it can be divided into piston aircraft, turboprop aircraft and jet aircraft; According to the number of engines, it can be divided into single-engine aircraft, twin-engine aircraft and multi-engine aircraft.

6. According to the type of landing gear, it can be divided into land aircraft, seaplanes and amphibious aircraft.

It can also be classified according to the flight performance of the aircraft:

1. According to the flight speed of the aircraft, it can be divided into subsonic aircraft, supersonic aircraft and hypersonic aircraft.

2. According to the range of the aircraft, it can be divided into short-range aircraft, medium-range aircraft and long-range aircraft.

The wing airfoil of the aircraft is not a plane, but slightly convex, the upper surface of the wing is convex and causes the upper surface air flow tube to shrink, the air flow velocity is accelerated, and the air flow on the lower surface produces a flow velocity difference, according to the Berlian equation, the greater the fluid flow velocity, the smaller the pressure, therefore, there is lift on the wing, when the aircraft is faster, the greater the flow rate difference, the greater the lift, when the lift exceeds gravity, the aircraft can take off.

Flying Principle 1. Glide.

The straight-line or curvilinear motion of an aircraft on the ground that does not exceed the specified speed is called taxiing.

The basic requirements for taxiing are that the aircraft starts taxiing smoothly, maintains speed and direction during taxiing, and enables the aircraft to stop at a predetermined position. The plane starts to move from a standstill, and the pull or thrust force must be greater than the maximum static friction force, so the throttle should be increased appropriately when the aircraft starts taxiing. After the aircraft starts to move, the friction decreases, so you should reduce the throttle as appropriate to prevent the acceleration from being too fast and keep the take-off and glide smooth.

In the coasting, if you want to increase the coasting speed, you should gently increase the throttle, so that the pull or thrust is greater than the friction force, produce acceleration, increase the speed, to reduce the coasting speed, you should retract the throttle, if necessary, you can use the brake.

Two. Takeoff.

The movement process of an airplane from the beginning of taxiing to leaving the ground and rising to a certain height is called takeoff.

The principle of maneuvering for the take-off of an airplane.

The aircraft glides from the ground to the ground and lifts off the ground as a result of the lift increasing until it is greater than the aircraft's gravity. And only when the speed of the aircraft increases to a certain point, it is possible to produce enough lift to support the gravity of the aircraft. It can be seen that the take-off of an airplane is an acceleration process with increasing speed.

The take-off process of the piston propeller aircraft with less residual pulling force can generally be divided into four stages: take-off and run, off the ground, small angle ascent (or a section of level flight), and ascent. A propeller aircraft with sufficient residual pull, or a jet aircraft with sufficient residual thrust, can accelerate and ascend the aircraft, so take-off is generally divided into three stages, namely take-off, ground departure and ascent.

a) The purpose of the take-off run is to increase the speed of the aircraft until ground clearance is obtained. The greater the pull or thrust, the greater the residual pull or thrust, and the faster the aircraft will grow. During takeoff, in order to increase the speed as soon as possible, you should push the throttle to the maximum position.

When the wing takes off, the speed increases because the upper wing is more curved than the lower and remains in a linear shape. If the speed is large, the flow rate will be large, and if the flow rate is large, the air pressure above will be greater than the air pressure below, so the downward air pressure wing will have an upward support force! Therefore, the take-off of the aircraft is based on the formation of the upper and lower air pressure difference.

Airplanes can fly by relying on the lift generated by the wings to take off.

Fixed-wing aircraft or fixed-wing aeroplane, often referred to as an airplane (English: aeroplane), refers to a heavier-than-air aircraft that flies in the atmosphere by the forward thrust or pull force generated by the power unit and lift generated by the fixed wings of the fuselage. It is one type of fixed-wing aircraft and is also the most common one, and the other type of fixed-wing aircraft is the glider.

Aircraft can be divided into jet aircraft and propeller aircraft according to the type of engine they use. On July 30, 1923, China's first double-decker propeller open-cover aircraft was successfully developed by the Guangdong Aircraft Factory.

How can an aircraft weighing several hundred tons fly? Don't believe it.

Turboturbojets, due to the high thrust of the engine, are generally divided into two phases when taking off, namely the "acceleration and climbing" phase. The end of takeoff is when the plane climbs to a height of 25 meters, and the height of 25 meters is artificially set to avoid the houses near the airport: to ensure the safety of the aircraft.

The take-off of a propeller aircraft can be divided into three stages: the first stage is the take-off run. The second stage is the level flight acceleration stage.

The third stage is the climb phase.

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, the air on the surface of the wing will become viscous if the speed is too large, and the Reynolds number should be taken into account, at that time there is another formula, which is very complicated.

The plane takes off by lift. In a real wing that generates lift, the airflow always converges at the trailing edge, otherwise there would be a point at which the airflow velocity is infinity at the trailing edge of the wing. This condition is known as the Kuta condition, and only when this condition is met can the wing generate lift.

In an ideal gas or at the beginning of the wing's movement, this condition is not met and a viscous boundary layer is not formed. Usually the airfoil (wing cross-section) is longer than the lower distance, at the beginning in the absence of circulation, the upper and lower surface airflow velocity is the same, resulting in the lower airflow to reach the trailing edge when the upper airflow has not reached the trailing edge, the rear station is located at a point above the airfoil, the lower airflow must bypass the sharp trailing edge and meet the upper airflow.

The principle of airplane flight is that the airplane relies on the difference in air pressure between the upper and lower wings to provide lift, because as long as the aircraft moves forward (whether taxiing on the runway or flying in the air), the air pressure under the wing will be greater than the air pressure above the wing.

The take-off process of a jet consists of three phases: ground taxi, ground lift, and accelerated climb. The aircraft first taxied to the take-off line, braked the wheels, put the flaps in the take-off position, and increased the engine speed to the maximum, then released the brakes, and the aircraft began to accelerate and slide under the action of thrust.

With the development of high-speed and heavy-duty aircraft, the ground clearance speed has increased significantly, and the runway length and take-off distance have been correspondingly lengthened. Atmospheric temperature, pressure, runway conditions, and piloting techniques all affect an aircraft's take-off performance. Taking off against the wind, increasing engine thrust, reducing wing loads, and using lift increases can shorten the running distance and improve take-off performance.

Heavy aircraft sometimes use thrusters to shorten take-off runs. Carrier-based aircraft use catapults to achieve short take-offs. In addition, the rotors, propellers, and fans can be driven directly by the power unit or by the power unit to generate thrust lift to support the weight of the aircraft and achieve vertical take-off.

Fixed-wing aircraft refers to an aircraft with wings, one or more engines, propelled by its own power, and capable of being denser than air in space or the atmosphere. If the density of the aircraft is less than air, then it is a balloon or an airship. If there is no power unit and can only glide in the air, it is called a glider.

The airplane is one of the most significant inventions of the early 20th century, recognized as invented by the American Wright brothers. Their flight on December 17, 1903, was recognized by the Fédération Internationale de Nautical (FAI) as "the first controlled, sustained powered flight of a heavier-than-air aircraft", and in the same year they founded the Wright Aircraft Company.