What function does the CREW RATIO knob provide?

The CREW RATIO knob is used to change the proportions of hot air between the left-hand and right-hand cockpit floor, allowing for better temperature regulation and comfort for the crew. This functionality is critical in managing the thermal environment of the cockpit, particularly in varying flight conditions and during different phases of flight. Crew comfort can significantly affect performance and decision-making, so having control over the distribution of heat helps ensure that both the pilots are adequately accommodated, especially when one side may require more heating than the other due to factors like sunlight or aircraft maneuvering.

Each of the other options describes functions that are typically managed through different controls or systems in the aircraft, illustrating that the CREW RATIO knob is specifically tailored for managing hot air distribution rather than those broader thermal or environmental aspects.