Overview
The function of the air system is to keep the engine at a satisfactory temperature, internally and below the cowling. Its function is also to make sure the compressor operates smoothly.
Air supplied by the LP compressor is divided into two flows. Some air flows through the bypass duct and some flows through the core engine. Bleed air comes from different stages of the HP compressor to keep the engine at a satisfactory temperature. Some of this air goes through ducts for engine anti-icing. Air also seals parts of the engine internally. Some bypass air helps to keep a satisfactory temperature in the accessory/fire zones and to remove flammable fumes.
It is necessary to control the airflow to make sure the engine operates smoothly through the power range. A system which automatically adjusts the volume and direction of the airflow through the compressor does this. At the same time, some air bleeds from two stages of the compressor to atmosphere.