When you ask people what the primary function is of a landing gear they largely say it is meant to land the aircraft, yet thats just what the words stands for. This is slightly appropriate, one of the three main functions is energy absorption (at getting). (1. 1. 1a). However when the aircraft has touched the ground it must stop, so here is an other main function of the getting items; braking (1. 1. 1b). The final step and also the last main function is made for taxi control, quite simply: to manoeuvre the aircraft on earth (1. 1. 1c).
When an aircraft has reached its vacation spot, it must descend and land on a runway from an airport terminal. To do this it is using the landing products of the aircraft. When the aircraft hits the ground the landing gear is the interface of aircraft to floor. Depending on various factors like: climate, aircraft fill, aircraft configuration and aircraft balance the getting products must absorb the impact energy and must transfer this lightly to the aircraft framework. However, not only at landing, when an aircraft is on surface while manoeuvring the landing gear has to bear the total weight associated with an aircraft and absorb the energy while braking, taxiing, take off roll, landing spin, steering and towing. With only a strut and wheels there is absolutely no chance of surviving a direct effect with a sizable aircraft. Which means landing gear is provided with distress absorbers. The distress absorber may be an unbiased element, or integrated with the getting items strut or in area braces. The tires of a getting gear are also used for shock absorption. Aircraft wheels are much more stronger as auto tires for automobiles. Getting gear tyres are made to resist high take-off and landing rates of speed and large great shock loads upon landings.
1. 1. 1b Braking
Another challenge of an landing gear is to avoid the aircraft while moving on the runway. The landing gear may use the tires to achieve this challenge. But the tires cannot stop by itself, they want brakes to decelerate. Virtually all commercial aircrafts have only brakes at the primary landing items to slow down the aircraft and use at each main gear wheel multiple disk hydraulic driven brakes. Those brakes are handled in journey deck. Pilots can make three inputs for braking; manual brake, car brake system and parking brake. The manual brakes are controlled by brake pedals mainly located near the top of the rudder pedals. The auto brake system provides computerized braking during take-offs and landings so the pilot can perform other tasks. The vehicle brake system can be placed in different settings to apply accurate braking configurations. To keep up position for a longer time on earth a auto parking brake can be used so the aircraft does not need wheel chocks.
1. 1. 1c Taxi cab control
The last function of the landing items is taxi control. To manoeuvre the plane on earth at low speeds the landing gear has steering facilities therefore the plane can move alone and do not have to get moved by the tug. At modern commercial aeroplanes the nose landing gear is equipped with a hydro-mechanical system to go the nose gear. Steering is performed by the pilot either from a tiller in the cockpit or the rudder pedals. Some aircrafts with an increase of than two main products products (bogies) need also to regulate these extra models to manoeuvre the airplane safely.
Landing items types
Not every airplane gets the same landing items configuration. To understand why modern commercial aircrafts use a tricycle products configuration (nose wheel equipped aeroplanes) there first will be viewed to other kinds of configurations (1. 1. 2a) to comprehend the benefits. Not only the benefits will be described but also the building of the tricycle gear configuration (1. 1. 2b).
1. 1. 2a Getting gear configurations
For aircraft technicians, the landing items is not their most liked part of an aircraft because it is not needed in flight but nonetheless it does impact the journey performance. Because the first aircraft technicians have tried all kind of configurations to fit best under an average aircraft. Each configuration has its advantages and disadvantages, to discover you will see take a look at several configurations available to engineers.
Taildragger gear
Bicycle gear
Single main gear
Quadricycle gear
Ad 1 Taildragger gear
The taildragger equipment also called a typical landing equipment (Physique. . . ) contains two main equipment devices (1) and a small wheel or skid to support the tail (tail unit) (2). This sort of construction ruled the plane design from about 1910 till 1950. Nowadays this settings is trusted on small propeller-driven aircrafts, because it's ease. Isn't only used because of its simplicity, it has additionally some benefits.
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Main gear units
Tail unit
Figure. . . : Taildragger items as seen on the Spitfire
The two main products units can easily be adapted to create low pull in air travel and because the tail wheel is small there is less weight. After you go through the taildragger settings (Physique. . . ) you will notice the nose of the aircraft is already entitled, therefore the wings curently have an larger perspective of attack. This means when the aircraft rolls down the runway the wings create more lift therefore the airplane needs less length of runway. Besides the propeller of an propeller-driven plane has a higher level above the bottom, what could save the propeller from damage.
But this settings does likewise have some disadvantages. The handling characteristics aren't that good. This is because the centre of gravity is situated behind the key gear units. Which could ends in a ''ground loop''. A ground loop is actually an uncontrolled switch while on earth. With all the centre of gravity behind the main gear devices, any change will naturally increase in rate because of momentum. When getting and using the brakes way too many at rollout, this may bring about a capsizing airplane. These cases could easier appear when one main items unit touches down first or with heavy crosswind. To avoid, pilots must fall into line a approach very carefully to keep the plane on a straight journey until it involves a stop, this is finished with constantly rudder modifications. Some aircrafts provide an locked tail device to keep moving in a straight line during landing.
Ad 2 Bicycle gear
The bicycle equipment consist of two main equipment units across the centre line of the aircraft and very often sideways two small outrigger gears mounted on the wing (Physique. . . ). This sort of configuration is not so common but is a solution for aeroplanes with lengthy and lean fuselages or high wing airplane. This configuration is in fact very limited to airplane with wings that create high lift up at a minimal angle of harm, as rotation with this construction is impossible.
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Main gear units
Outrigger gear
Figure. . . : Bi-cycle gear as seen on Boeing B-47
Only one of the benefits is lower weight and drag than the taildragger or tricycle construction.
For the pilot this construction is challenging, because she or he must maintain an extremely level attitude during take-off and getting while carefully controlling airspeed. The pilot has to land the plane without any rolling movement because that might lead to the airplane to land on one of the outrigger equipment.
Ad 3 Single main gear
The one main products (Amount. . . ) contain one main items unit (1) and a much smaller auxiliary tailwheel (2) over the centreline. For stability an outrigger equipment (3) is mounted over the wing. This configuration is nearly the same as the bicycle products and is practical for use on light planes like gliders. The one main gear is merely like the bicycle gear lightweight and low drag.
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Main items unit
Auxiliary tailwheel
Outrigger gear
Figure. . . : One main items as seen on a Lockheed U-2
Ad 4 Quadricycle gear
The quadricycle products (Body. . . ) consist of four main gear units (1) about mounted along the fuselage. This settings is also similar to the bicycle items and has been used sometimes on cargo plane. For cargo plane maybe it's ideal because the aeroplanes floor can reach a very low level above the bottom what is straightforward for loading or unloading cargo.
Just like the bicycle configuration the pilot must maintain an extremely level frame of mind during take-off and getting. A quadricycle equipment is also very delicate for spin, crosswinds, and proper fall into line of a procedure. The Boeing B-52 comes with an extra crosswind products (2) installed to make crosswind landings. A major disadvantage also is four main items units which contain a much higher weight and drag.
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Main products units
Crosswind gear
Figure. . . : Quadricycle items as seen on the Boeing B-52
1. 1. 2b Tricycle Gear
The tricycle products generally consist of two main products models and one nose area gear product. Nowadays this type of configuration is mostly used in aviation especially for commercial aeroplanes. The tricycle settings has one steering wheel in leading and two or more main tires located close to the centre of gravity. The main reason why it is mostly used is the ease of operating the tricycle gear aircraft on ground. This is not the only edge the tricycle products has a series of advantages:
stability in braking
steady touch down without threat of aerodynamic jump (like taildragger equipment)
high pilot presence during taxiing (because of level aircraft)
horizontal floor (people comfort and easy cargo launching)
low drag during take-off acceleration
The tricycle gear has more configurations (Number. . . ). The most frequent (& most simple) has a double main landing gear unit and solitary nose gear product (1). For some airplane this is good enough to tolerate the aircraft weight. For airliners beyond 300. 000 kg of maximum take-off mass you can find need for an extra landing gear product located under the fuselage (2), or even two main getting gear products located under the wing (3). That is needed to make the top pressure on all landing gears suitable.
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Figure. . . : Tricycle items configurations
Those extra landing gear units are called bogies. When an aeroplanes has extra landing gear systems it is named a multi-bogie products configuration. The heavier the airplane becomes, a lot more wheels are added to the bogie to spread the surface pressure on the runway pavement. The nose wheel could also get an extra steering wheel or even a supplementary nose gear product.
Unfortunately the tricycle products configuration has a larger weight and pull as a result of large nose wheel gear device. Aircrafts with a tricycle construction almost always require retraction mechanisms to lessen drag. Another challenge at tricycle products configurations is building a properly balance fill by the key gear versus the nasal wheel. Once you will put too little load on the key wheels, braking effectiveness will reduce. When putting too little insert on the nasal area wheel the aircraft is sacrificing its steering efficiency. Loading the aeroplanes must be carefully done to balance the aircraft to avoid the plane from street to redemption over on its tail.
