Pneumatic systems are also known as vacuum or pressure systems, the power of many functions that are important for the aircraft. Electric instruments, platforms, windows, air conditioning, doors and autopilot devices are some of the many operations that work with pneumatic system. The pneumatic and hydraulic systems are similar and use compressed fluids. The property of the fluid can be liquids such as water, oil or something that flows. And both fluids and gases flow, since they are considered fluid; however, there is a big difference in the characteristics of the two.
Liquids can not be compressible; One liter of water still occupies about a quarter of a gallon of space, regardless of the force with which it is compressed. But the gases can be compressed, a quarter of air can be compressed in a lot of space. Taking into account these differences, gases and liquids are fluid and can be made to transmit power. The type of unit used to provide pressurized air for pneumatic systems is determined by the system's air pressure requirements.