What is the function of the CABIN ALT knob?

The CABIN ALT knob primarily functions to increase or decrease the cabin altitude during manual pressurization. This knob allows pilots to manually adjust the cabin pressure to maintain a comfortable environment for passengers and crew, especially during ascent or descent phases when automatic systems might be overridden or require manual input.

When the aircraft climbs, the CABIN ALT knob can be used to manage the cabin pressure to ensure it matches the external atmospheric conditions while keeping within safe operational limits. Adjusting this setting is crucial in scenarios where precise control over cabin pressure is necessary, such as in response to unexpected changes in altitude or performance of the pressurization systems.

It’s important to note that while some functions like depressurization or emergency release are crucial for safety, they are not the primary purpose of the CABIN ALT knob during normal operations. The other options do not accurately describe the core function of the knob in the context of cabin pressurization management.