In modern aircraft, the flying performance, design of the airframe, engines, armament, or the military purpose are the features of principal interest, while the efficiency of the undercarriage is usually known only to a limited number of specialists. Shock-absorber legs, wheels and brakes are now such highly developed structural components that they deserve special attention. In the following, modern types of wheels and bra kes are described in detail and following, modern types of wheels and brakes are described in de the theoretical basis for the calculation of the landing process discussed.

Economical organisation and practically inexhaustible supplies of raw material in our country create exceptionally favourable conditions for the rapid development of the plastics industry. The raw material is drawn from the by-products of various branches of the chemical and agricultural industries.

By their technical properties, plastics present many advantages over many other materials. Some of them are as strong as metal, as transparent as glass, and as light as wood. Plastics are endowed with high dielectric properties, great thermo-stability, and low conductibility for sound and heat; they can be machined, pressed, moulded, and have a pleasing exterior.