Aircraft braking during landing
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Aircraft braking during landing

Airplane braking during landing

 

To safely land the aircraft is extremely important service brake. Reducing the landing distance is possible when using a variety of devices, from standard brakes to aerodynamic complex devices. The most common method of braking is considered aerodynamic. In this case, a sharp increase in the drag of the aircraft is applied. For aerodynamic braking, most airplanes in the implementation of landing are put forward brake special shields. In other types of aircraft, they are mounted in different ways:

  1. On the bottom or top surface of the wing.

  2. On each side of the fuselage.

  3. In the lower part of the fuselage.

It is much more pronounced use of the braking parachute. Such an arrangement is thrown on strong straps made of a special container, which is in the tail of the aircraft. Parachute quickly filled with ram air and dramatically slows down the ship, which significantly reduces the length of the landing run. In some cases, such inhibition reduces to 60% of the runway.

The braking force produced by the parachute is proportional to the square of the velocity. For this reason, the parachute should be released immediately after the moment of landing. Thus, the efficiency of the process increases. To release the parachute, the pilot, using a hydraulic or electric drive, opens the compartment in which the parachute pack is located. After that, an exhaust chute is thrown out, which draws the dome and the lines of the main parachute. There are different systems of brake parachutes: cruciform, belt and with circular slots. It is very important that the dome has sufficient air permeability. This provides the necessary stability and excludes the possibility of rocking the aircraft. However, at the same time, air permeability should not be too large, since the braking force can be greatly reduced.

As a rule, the parachute is attached to the aircraft through a shear pin. In the event that there is a big overload, it is cut off, preventing the flow of very high voltages. Brake parachutes experiencing a huge load and therefore wear out quickly. If the wind blows side, their use difficult.

beautiful landing

Operating braking parachutes in the domestic aviation began about 70 years ago. In 1937 year to deliver the high latitudes of the Arctic Soviet aircraft used a braking parachute. However, while their operation is calculated purely on military aircraft.

Almost all passenger and military aircraft have a wheel brakes. The principle of operation is not very different from car brakes. The only difficulty lies in the fact that the brakes of the aircraft wheels during braking must absorb huge amounts of energy, especially when braking heavy types of aircraft that have high landing speed.

On deceleration speed is directly proportional to affect power brakes, experience and skill of the pilot, the coefficient of friction of pneumatics. Effectiveness depends on the ability of the wheel brakes to absorb and dissipate the resulting heat during the braking process.

In 20-ies in the air began to spread spacer drum brakes. Coated soft organic material to brake pads pressed against the inner surface of the drum cylinder of mild steel. But the energy consumption of such brakes is not sufficient even to light aircraft. They replaced the brake chamber. They had a cylindrical drum. Pads are replaced with plates of frictional material arranged around the circumference on the surface of the rubber ring chamber.

During braking, the chamber under pressure is liquid or air. As a result, the plate pressed against the inner surface of the drum. So use the entire circumference of the brake drum, provides uniform contact surfaces.

But the chamber brake are ideal for large wheels and chassis operation multiwheel trucks or wheels of small diameter led to the need to create a new type of brake. Thus designers invented disc brakes.

When small amounts of these different brake high energy and can develop a strong braking force. They are excellent for forced cooling. Disc brakes multitype and is still used in the world of aviation.

plane landing

The multi-disc brake consists of several fixed thin discs that alternate with rotating discs. Between disks in the disinhibited state there is a gap and a wheel. When braking, the disks are compressed, rub against each other and develop the braking force. Even a small volume multi-disk brake can absorb a lot of kinetic energy. In addition, there are single-disk brakes with fixed friction liners, located in pairs on both sides of a strongly rotating disc. During braking, each pair is pressed against the disk by a piston of a hydraulic separate cylinder.

In the original designs of these brakes discs made of low-carbon steel were used, and after that they were replaced by alloy wheels, which retained hardness and wear resistance in a wide range of temperatures. Frictional pairs to alloys have become perfectly suited for cohesion in the method of cast iron and bronze. The addition of various additives - ceramics, graphite, aluminum oxide and others - affects the physical and mechanical properties of the material. To reduce the weight of brakes, engineers and scientists are looking for new materials. Wheel brakes with curved heat treatment materials have been created. They are covered with reinforced carbon fibers. Each such brake is much lighter than usual and retains its strength at high temperatures.

The new brakes persists vibration, creaking and uniformity of braking. These brakes have strong resistance to wear. Modern wheel brake absorb large amounts of energy. For example, the multi-disk brake wheel aircraft "Boeing-707» absorbs 6,15-106 kg * m kinetic energy. Due to the allocation of a large quantity of heat is very often necessary to protect the installation housing and wheels bus special heat shields and the use of artificial cooling disks.

In some brake designs blown huge amount of air which is supplied from the compressor motor in the other water spray is applied specifically to the disks. There are also special circulation system with heat exchangers. In the initial stage mileage wheel brakes ineffective. At low speeds, the aerodynamic brake is applied, which at higher speeds create more stress. Thus, the wheel brakes and aerodynamic interact.

The landing conditions differ among themselves depending on the state of the runway (runway), weather and other. Therefore it is extremely important, how much the pilot masterfully possesses ability of braking. As a result of a lot of refinement of the research on aircraft, braking automatons were installed, which make it possible to achieve the coefficient of friction of pneumatic elements. The coefficient of friction, which is obtained by the operation of the braking automaton, can be twice as large as its value. The efficiency of braking increases with increasing load on the wheels, which is why it is very important to reduce the lift of the wings faster after landing. Flaps are removed immediately.

For turboprop and piston aircraft has long been applied braking thrust reverser screws. Before planting, changing the angle of the blades. Screw attached to a negative value, which then leads to a rearward thrust. Even more effective is a reversal of the thrust on the aircraft with turbojet engines. After the turbine engine gas flow is directed opposite to the original motion. It produces negative thrust, the aircraft braking.

plane parachute

Thrust reverser allows the braking of the aircraft, not only during the run, but also directly in the air before landing. This in turn leads to increased reduction of the landing distance. There are gas-dynamic and mechanical methods of deflection for reverse thrust. In a first embodiment the flow is deflected by means of a jet of compressed air in the second - part of the gas flow is deflected deflectors. By creating a reversible device, designers take care that the flow of hot gas without melting skin of the aircraft.

All of the above on-board braking facilities allow you to greatly reduce the length of the run at landing, but still it remains relatively large. A drastic reduction in the mileage is possible with the use of stationary devices installed at certain aerodromes (mainly aircraft carriers). Basically, such delay devices are represented by strong cables - aerofinisher. They stretch across the runway at an altitude of 10-15 cm above the deck of an aircraft carrier or a runway. Through the system of blocks, the ends of the cables are connected to the pistons of the hydraulic power cylinders. During landing, the aircraft hooks onto the cable with the hook installed. The bulk of the kinetic energy of the aircraft is spent on the advancement of the piston in the cylinder. Through 20-30 m the aircraft stops.

 

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