Aircraft Cabin Environmental Control Systems

Throughout the operation of an aircraft, whether on the ground or in the air, the crew and passengers must be kept in comfortable conditions. They must be neither too hot nor too cold, they must have air to breathe and they must be kept in comfortable atmospheric pressure conditions. This is by no means easy, given the rapid changes in climatic conditions and internal temperatures seen by aircraft in flight from one destination to another.

The environmental control system must cope with widely differing temperature conditions, must extract moisture and provide air with optimum humidity, and must ensure that the air in the aircraft always contains a sufficient concentration of oxygen and that it is safe to breathe.

Modern systems do this and more, for the term ‘environmental control’ also includes the provision of suitable conditions for the avionic, fuel and hydraulic systems by allowing heat loads to be transferred from one medium to another. In addition to these essentially comfort related tasks, environmental control systems provide de-misting, anti-icing, anti-g and rain dispersal services.

Major design drivers for the environmental control system are thermal comfort, pressurization and cabin air quality. However, these parameters cannot be considered independently. They interact between themselves and with other parameters, which may or may not be controllable by the system designer. These interactions occur in a highly complex manner. Research has led to a good understanding of the basic functions to allow safe and comfortable aircraft environmental conditions.

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