1) Framed landing gear: used in early small aircraft, consisting of pillars, struts, shock absorbers, wheels and other parts. Can only bear axial force, can not bear the bending moment, use rubber block or spring, elastic rope to absorb shock.
2) Pillar landing gear: The structural type commonly used in modern aircraft consists of shock absorbing strut, retracting actuator, axle, torsion arm, brake device and wheel. The shock absorbing strut is the main part of the landing gear, which functions as parking support, sliding and landing damping. The working medium in the shock absorbing strut (or shock absorber) is hydraulic oil and compressed air. The retractable actuator acts as a transmission when retracting, and the function of the torsion arm is
a) preventing the inner and outer cylinders of the shock absorbing strut from rotating relative to each other;
b) When the landing gear is subjected to the lateral force, the anti-torsion effect is applied, and the wheel and the brake device are installed on the axle.
3) Rocker-type landing gear: It is characterized in that the pillars are separated from the shock absorbers and function separately from each other. The lower ends of the pillars are hinged to the rocker arms, and the lower part of the rocker arms has axles for mounting the wheels and brakes. When the wheel is hit by landing or sliding, the rocker arm is rotated around the hinge point, thereby compressing the shock absorber (the upper end is connected with the pillar and the lower end is connected with the rocker arm), and the shock absorption effect is superior to the pillar type. Because of the low structural height, it is mostly used by jet fighters.
4) Multi-wheeled (small car type) landing gear: adopted by large aircraft, the basic structure type is pillar type, the lower wheel frame, the wheel frame has front and rear axles, and two sets of wheels (including brakes) are installed at both ends of the axle. The wheels are arranged in a trolley (there are also 4 wheels arranged in a row). The purpose is to distract the forces. There are auxiliary shock absorbers in front, and some have no runner mechanism to avoid the phenomenon of dragging.