Landing gear - a system consisting of columns, which allow the aircraft to carry out the parking lot, moving cars, or water aerodrome. With this system is landing and taking off of aircraft. The system consists of a rack chassis on which are mounted wheels, floats or skis. It should be noted that the term "chassis" is quite extensive, as some components of the racks, and they may have a different structure.
The chassis is required to meet the following specific requirements:
Handling and stability of the vehicle when moving on the ground.
Have the necessary throughput and not to cause damage to the runway.
Should allow aerial vehicles to carry out turns on 180 degrees when taxiing.
Eliminates the possibility of tipping the aircraft or touch other parts of the machine, except the chassis when landing.
The absorption of impact forces during landing and traveling over rough terrain. Fast vibration damping.
Low levels of resistance in the run-up and high braking performance when run.
Relatively quick cleaning and production of chassis systems.
Have an emergency release system.
Exclusion of oscillation racks and gear wheels.
The presence of the alarm system on the status of the chassis.
In addition to these indicators, landing gear must meet the requirements to the entire structure of the aircraft. These requirements are:
Strength, durability, rigidity at minimum weight display.
The minimum aerodynamic resistance of the system in the retracted and extended position.
High rates of technological design.
Durability, comfort and economy of the operation.
Varieties chassis systems
1) wheeled chassis
Wheel chassis may have a different circuit layout. Depending on the application, design and weight of the aircraft designers have resorted to the use of different types of racks and the arrangement of the wheels.
Location wheel chassis. Basic schemes
Tailwheel landing gear, often referred to as a two-post scheme. In front of the center of gravity are two main support and the auxiliary support is behind. The center of gravity of the aircraft is located in the front struts. This scheme was used by planes during World War II. Sometimes the tail wheel had no wheels, and was represented by a crutch, which slipped on landing and served as a brake on the unpaved airfields. A striking example of this scheme is the chassis such aircraft as the An-2 and DC-3.
The chassis with the front wheel, such a scheme is also called the tricycle. For this scheme was established three racks. A bow and two behind, and cling to that center of gravity. The scheme began to be used more widely in the postwar period. An example of the aircraft can be called Tu-154 and Boeing 747.
The system of bicycle landing gear. This scheme involves placing two main bearings in the body of the aircraft fuselage, a front, and the second behind the center of gravity of the aircraft. There are also two legs on each side, near the wing tips. This scheme allows you to achieve high performance aerodynamics of the wing. In the same place there are difficulties with the technique of landing and location of weapons. Examples of such aircraft are Yak-25, Boeing B-47, Lockheed U-2.
Multibasic chassis used on aircraft with a large take-off weight. This type of gear allows to evenly distribute the weight of the aircraft on the runway, which reduces the degree of damage to the strip. In this scheme, the front can be two or more racks, but this reduces the maneuverability of the machine on the ground. To improve the maneuverability of multibasic apparatus main supports can also be controlled as nasal. Examples multiterabit aircraft is IL-76, «Boeing-747».
2) ski gear
Ski gear is used for aircraft landing on snow. This type is used in airplanes for special purposes, usually a car with a small mass. In parallel with this type can be used and the wheels.
The components of the landing gear
Depreciation rack ensure smooth progress of the aircraft during the escape and acceleration. The main task is damping impacts on landing. The system uses a nitrogen-oil type shock absorbers feature spring carries pressurized nitrogen. To stabilize the dampers are used.
Wheels mounted on planes, may vary according to the type and size. Wheel drums are made of high-quality magnesium alloy. The local offices of their stained green. Modern aircraft are equipped with pneumatic type wheels without cameras. They are filled with nitrogen or air. Wheel tires have a tread pattern excepting longitudinal drainage grooves. Using them as fixed degree of deterioration of rubber. Incision tire has a rounded shape, which allows maximum contact with the web.
Pneumatics aircraft equipped with drum or disc brakes. Brakes drive can be an electric, pneumatic or hydraulic. With the help of this system reduces the path length after planting. Aircraft equipped with a large mass of multi-drive systems to improve their effectiveness establishes a system of forced cooling type.
The chassis has a set of rods, hinges and braces that allow fixing, cleaning and release.
The chassis is removed in large passenger and cargo aircraft and combat vehicles. As a rule, have a fixed landing gear aircraft with low speed and low mass.
Issue and retraction of the aircraft
Most modern aircraft are equipped with hydraulic drives for cleaning and landing gear. Prior to that used pneumatic and electrical systems. The main system components are the cylinders, which are attached to the front of the aircraft and the body. To fix the position of using special locks and spacers.
Designers aircraft trying to create the most simple system chassis that reduces the degree of damage. Still, there are models with complex systems, can serve as a vivid example of Tupolev planes. When cleaning the chassis machines Tupolev it rotates 90 degree, it makes for a better placement in niche gondolas.
To fix the rack in the retracted position using locking hook type earring which latches disposed at the front of the aircraft. Each aircraft has a system of signaling the position of the chassis, with the released position lamp is green. It should be noted that lamps are provided for each of the supports. When cleaning rack illuminates the red lamp goes out or just green.
The production process is one of the most important, so the planes are equipped with additional systems and emergency release. In case of failure of the main rack release systems use alarms that fill cylinders with nitrogen under high pressure, which ensures release. In the extreme case, some aircraft have a mechanical opening system. Release racks across the flow of air allows them to be opened by its own weight.
Light aircrafts have a pneumatic braking system, apparatus with a large mass equipped with hydraulic brakes. Management of the system is a pilot from the cockpit. It is said that every designer has developed its own braking system. As a result, there are two types, namely:
Trigger lever, which is mounted on the control stick. Pressing the trigger pilot leads to inhibition of all-wheel machine.
The brake pedal. The two cockpit mounted brake pedal. Pressing the left pedal to brake the wheels left side, respectively, the right pedal controls the right side.
Racks aircraft have antiyuzovye system. This saves the wheel of the aircraft from explosions and fire at landing. Domestic cars were equipped with the releasing equipment with sensors inertia. This allows you to gradually reduce the speed by gradually enhance braking.
Modern electric automatic braking allows you to analyze the parameters of rotation, speed and braking to choose the best option. Emergency braking of aircraft carried out more aggressively, despite antiyuzovuyu system.
What happens if you sit without chassis
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