Two kinds of landing gear

Answer 1

There are many different kinds of landing gear that can be categorized by their geometry and their internal design. There are fixed landing gears that do not retract. These are usually a support that is made of spring steel that has a axle for a wheel. This example is found on small Cessna aircraft. Other fixed landing gear that are attached at a pin joint and have a shock strut to absorb landing loads. Helicopters are good examples as many have a fixed landing gear. The simplest landing gear shock strut is designed to stroke and absorb energy and it has an axle for either 1 or 2 wheels. These usually rotate on a trunnion at the top of the gear to allow retraction by pivoting of the entire gear. A drag brace locks it down into position. Larger gear have a bogie beam or pivot beam that have multiple wheels, either 4 or 6. The bogie beam attaches to the shock strut and is allowed to pivot during landing and taxi. It will have an actuator or locking mechanism to hold the bogie beam in proper position to allow it to retract in to the wheel well. Internal Design The simplest design is the lower half of the strut(called the Piston) is designed to stroke into the upper half (Outer Cylinder). As it does, the piston forces the fluid through an narrow opening (orifice) that restricts the movement and allows the gear to absorb energy. Many Nose landing gears are of this simple design. Other gear designs will allow the Piston to stroke to a point where it contacts a 2nd Stage. This 2nd stage will have higher pressure or an enclosed volume of air that acts as a final cushion to stop the gear. Some gears have a 2nd Chamber at the top of the gear that has its own piston and orifice. As the Piston strokes, the internal pressures build up and push against the 2nd Stage and it begins to stroke and also resist the forces. This example is found in the DC10 or MD11 Main landing gear.

Answer 2

In general one type is with one tail (skid) wheel mostly in small and old type aircraft. Present day most off the planes have tri-cycle type of landing wheel configuration. To further classification is fixed and retractable , one with float for landing on water and enclosed wheel for landing on ground.