Landing gear are a part of a plane which helps it to move when not in flight . It makes it possible to land and take off of  an airplane  . And generally the landing gears don’t only have tiers , there are skids that are used in the landing of an helicopter , there is skis which allows the planes to land on ice and after take off they retract , and the planes can be landed on the water too with the use of a landing gear called floats these floats will help to keep the plane afloat on the water . But in a typical aircraft usually wheels are involved with shock absorber . These shock absorbers are used to absorber the force of impact and they push the wheels towards the ground for a better contact with the ground . There are many types of shock absorbers used .

They are shock absorbers that is a combination of pressurized air and oil . This mechanism is attached to the wheel this absorbs the impact forces that is experienced while landing . Because if there were no suspensions then the impact force is not absorbed but it pushes the ground as a reaction for the impact force that allows the plane to bounce and lose control .

And in lighter aircrafts there are rubber disks used instead of olio struts , and even simple spring steel bar or steel bar used to absorb the impact force .

The aircraft tier can withstand up to 250 to 1000 times the normal pressure experienced by a passenger car . And the temperature can fall up to -50 degree during the flight and reach up to 60 degrees during landing on runways due to the friction . The threads on these tiers are made in such a way that it removes the water and improve its friction . The main materials used in these tiers are rubber , Nylon chord , and steel  . They are bounded together by a process called vulcanisation .

Conventional landing gear or tail wheel type landing gear . In this arrangement there are 2 weeks slightly in front of the centre of gravity of a plane because during the landing of the plane it should not topple over . And there is a smaller wheel supporting the tail called the skid . They are cost efficient and easier to handle or maintain . As the nose wheel ( main wheel ) supports most of the weight , the skid supports lesser weight and hence it can be made smaller and lighter , this in turn reduces the drag . This type of arrangement is able to sustain a larger duration of use even on rough grounds because of its structure . But there are a few disadvantages to this assembly , it is more subjected to nose over ( tipping over,) . As this arrangement is tilted upwards there is a poorer ground visibility . And the other arrangement of the landing gears is the tricycle gear arrangement . In this arrangement the nose wheel is in the front and the main wheel is slightly away from the centre of gravity . They are the easiest to land and take off that is why they are most used landing gear arrangements . In this as the plane is not tilted up the visibility is much better. And this much easier to land.