Aircraft air conditioning

Air conditioning systems create a safe and comfortable environment for passengers and crews inside the aircraft cabin: significant amounts of cooled fresh air are hence brought into the pressurized cabin in order to maintain a comfortable cabin environment and also to ensure avionics and electronics ventilation and/or cooling. The air conditioning system processes high pressure, high temperature air which is most of the time taken or “bled” from the aircraft engines (engine bleed air system). The core of the air conditioning system consists of air conditioning packs based on the so-called air cycle machines using air bearing technology allowing higher reliability. These air cycle machines are usually pneumatically driven but can also be either electrically or mechanically driven. Various components like heat exchangers, re-heaters, condensers, water extractors, flow control valves, sensors or controllers are also part of the system. Once the cooled air is blown into the cabin, it needs to be ducted to the appropriate zones and circulated in the cabin. This is accomplished by the so-called cabin distribution system. Ventilation and heating Some consumers may require local ventilation. This function is performed by the ventilation control system, basically made of electrically driven fans, valves, sensors, controllers and software. Some others may require local cooling. This is typically ensured by a vapor cycle system. Various components like compressors, heat exchangers, evaporators, condensers, water extractors, sensors and controllers are part of the system.