Warm, pre-conditioned bleed air enters the cooling path through the pack flow control valve and is directed to the primary heat exchanger. The air is then cooled before entering the compressor section of the air-cycle machine, where it is compressed to a higher pressure and temperature.

After compression, the air is cooled again in the main heat exchanger before entering the turbine section, where it expands. This expansion generates power to drive both the compressor and the cooling air fan. The removal of energy during this expansion process significantly reduces the air temperature, resulting in a very low air temperature at the turbine discharge.