ATPL Airframe Practice Test 2025 - Free ATPL Airframe Practice Questions and Study Guide

In a cabin air conditioning system that utilizes an air cycle machine, the mass airflow is routed from the secondary heat exchanger outlet to the turbine inlet. This routing is essential for the operation of the air cycle machine, which employs principles of thermodynamics to condition the air in the cabin.

The airflow process begins in the secondary heat exchanger, where the air has been cooled and dehumidified before reaching the turbine. When the conditioned air exits the secondary heat exchanger, it is at a lower temperature and pressure. Routing the air to the turbine inlet allows the turbine to expand the air, significantly reducing its pressure and temperature further. The process of expansion in the turbine ultimately helps in cooling the cabin air, contributing to effective air conditioning.

Understanding this airflow path is crucial because it impacts the overall efficiency and effectiveness of the air conditioning system, ensuring that passengers experience a comfortable environment during flight. Proper airflow routing through the components maintains the necessary thermodynamic cycles that provide adequate cooling by utilizing the principles of compression, expansion, and heat exchange.