Aircrewman Mechanical (AWF) Test 2 Practice

Cooling and dehumidifying cabin air is done by the air cycle machine. It takes bleed air from the engines or APU, cools it through heat exchangers with ram air, then expands it in a turbine inside the ACM. This expansion lowers the air temperature and removes moisture, giving cooled, dry cabin air. The environmental control unit oversees and routes conditioned air, but the actual cooling/heating work is performed by the ACM. The heater core provides heating when needed, not cooling, and the bleed air valve simply controls how much bleed air is supplied.