What is regulated by the Cooling Air Control Valve (CAV Valve)?

The Cooling Air Control Valve, commonly referred to as the CAV Valve, specifically regulates the flow of air across the heat exchanger. This component plays a vital role in managing the temperature of air that is directed to different parts of the aircraft, particularly in the cooling system. By controlling the amount of airflow over the heat exchanger, the CAV Valve ensures that the temperature of the air being circulated within the cabin or to other systems is maintained at an optimal level.

When the CAV Valve adjusts the airflow, it influences how effectively heat is absorbed or dissipated, which is crucial for maintaining comfort for passengers and proper functioning of onboard equipment. This regulation of airflow not only aids in temperature control but also in overall system efficiency and performance.

In contrast, the other options refer to different functions that are not the primary responsibility of the CAV Valve. The temperature of the cabin air is indeed affected by the flow of air across the heat exchanger, but it is not what the CAV Valve directly regulates. The isolation of engine bleed air pertains to a different system that manages the pressurized air taken from the engine, while the pressure within the fuel lines is a concept linked to fuel management systems, unrelated to the operation of the CAV Valve.